Future (“long-term”) side effects from COVID vaccines are extremely unlikely

Concern over unknown, future side effects is by far the most common reason I hear people give for why they aren’t vaccinating against COVID. At a quick glance, that may seem reasonable, but when you start really looking into the science, it quickly becomes clear that there is simply no reason to suspect that there will be dangerous long-term consequences of these vaccines. Indeed, based on everything we know about the immune system, vaccines in general, and these vaccines specifically, it is extremely unlikely that they will cause unknown, serious, wide-spread side effects in the future, and the known risks from COVID far outweigh the hypothetical risks from the vaccines.

In this post, I’m going to carefully go over the science and logic that allows us to be so confident in the long-term safety of these vaccines, but before I do that, I want to briefly explain who my target audience is here, namely, the “vaccine hesitant.” I am refereeing to the people who usually would not consider themselves “anti-vaccers” and would usually vaccinate themselves and their children but have been swept up in the maelstrom of misinformation and fear about the new COVID vaccines. If you are someone who is truly seeking information and trying to think for yourself, then please hear me out and seriously consider the arguments and evidence that I am going to present. Do not give in to the baseless fearmongering that is rampaging through the internet and media.

To that end, I want to point out right at the start that this tactic of stirring up fear of future, unknown, long-term consequences is not new or unique to COVID vaccines. It is straight out of the traditional anti-vaccine playbook. It is something I was writing about long before COVID, and the argument is just as flawed now as it was then. So, if you are someone who eschews the title “anti-vaccer,” but are avoiding the COVID vaccines because of the arguments about unknown, long-term effects, please realize that these are not new arguments that arose out of legitimate concerns specifically about COVID vaccines. Rather, stoking fear of future unknowns is a standard (and flawed) anti-vaccer tactic that they have been using for decades and are now dressing up and presenting as if it is a novel concern for COVID vaccines. Do not be fooled by this tactic.

This post is necessarily long, because there’s a lot to talk about in order to cover this topic properly, but, again, I have written this for people who are truly trying to think for themselves, and are truly seeking information. So if that is you, please read this carefully in its entirety.

Because of the length of this post, I will summarize key points in bullets below, before elaborating on each of them.

Summary: TL;DR

  1. mRNA vaccines have been being studied for over a decade (including human trials).
  2. Current COVID vaccines have been extremely well studied, with sample sizes of hundreds of thousands of people, and studies have been compiled into large meta-analyses/systematic reviews. Thus, the short-term risks of the vaccines are extremely well-documented, and the benefits outweigh the risks. The only “unknown” is about long-term effects; however…
  3. No vaccine has ever caused the type of widespread, serious side effect years down the road that everyone is afraid of.
    1. Nearly all side effects occur shortly after vaccination (see #2).
    2. The only example of a sided effect that showed up months later appear within a year (whereas we’ve been using COVID vaccines for over a year) and was rare. The vaccine benefits still outweighed the risks.
  4. Vaccines rarely cause long-term (future) side effects because they use low doses over a short time.
    1. Vaccines simply train your immune system.
    2. Vaccines are quickly removed from the body.
    3. Most vaccine components were well-studied, and their safety is known.
    4. mRNA:
      1. mRNA does not alter your DNA.
      2. mRNA is very quickly broken down and removed.
      3. mRNA in vaccines cannot make your body produce entire viruses.
      4. You are constantly exposed to mRNA from viruses (e.g., from colds)
      5. If you catch COVID, your cells will use viral mRNA to make proteins just like they do from the vaccine, but…
        1. Your cells will make entire viruses, not just a single protein.
        2. You will be exposed to far higher levels of mRNA.
    5. Side effects from immune stimulation will usually happen right away and will usually be worse from actual infection with COVID.
  5. A demand for long-term studies is meaningless unless you can justify why a particular length of time is needed.
    1. No matter how long something has been studied, it is always technically possible that an effect won’t show up until slightly after the length of that study.
    2. This is true for all medications, foods, minerals, vitamins, etc., yet we don’t fear most of them.
    3. Therefore, you must provide actual evidence or reasoning to think that a futre side-effect is actually likely.
  6. Focusing on a highly-unlikely, unknown, hypothetical risk from the vaccine while downplaying the very real and serious risk from COVID is bad risk assessment.
  7. Fears over unknown long-term effects of the vaccines are baseless. The burden of proof is on anyone claiming that the vaccines are dangerous.

Not as new as you might think

Before we go into the details of the COVID vaccines, we need some background information to put them in context, and I think it is important to point out that these vaccine technologies are not as new as people are often led to believe. Sure, these exact vaccines were developed recently, but mRNA vaccines have been being developed and tested for years. Thus, the underlying technology is well-studied.

Let me direct you to a review paper published in 2018 (before COVID) titled, “mRNA vaccines — a new era in vaccinology” (Pardi et al. 2018). This review covers over a decade of research on mRNA vaccines, including safety and efficiency trials on mice (Fleeton 2001; Geall et al. 2012; Magini et al. 2016), ferrets (Brazzoli et al. 2015), pigs (Schnee et al. 2016), monkeys (Brito et al. 2014), and yes, even humans (Craenenbroeck et al. 2015; Bahl 2017; Alberer et al. 2017). As you’d expect in a rapidly growing field, even more studies were published following that review, (but prior to COVID). Feldman et al. (2019), for example tested mRNA influenza vaccines in over 200 people, including following them for a full year after the vaccines to assess safety and effectiveness. Similarly, studies like Alberer et al. (2017) followed patients for a year prior to publishing and continued to follow them after publication.

To be clear, those human trials were small trials; my point is simply that we were able to develop these COVID vaccines so quickly not by rushing, but rather by utilizing a robust body of research that had already been conducted. All of the information was there, waiting to be applied to something like COVID.

The way that people (including politicians and the media) are talking about these vaccines, you’d think that they represent totally uncharted territory. Reading the comments on my page, people are acting like we have almost no knowledge about them and are shooting in the dark, recklessly plowing into the unknown, but that’s simply not true. In reality, we knew a ton about mRNA vaccines before COVID, and that should really change your perspective on these vaccines.

It is so easy to give into fear of the unknown, particularly when you are so constantly bombarded with people’s concerns. I don’t blame anyone for that;’ it’s human nature, but it’s important that we use logic and facts to overcome our base fears, and if you step back and start to rationally look at the wealth of knowledge these vaccines were based on (including human trials spanning a year or more), that really should paint these vaccines in a different light and help to alleviate those fears.

Note that I only cited a small handful of the studies that had been conducted prior to COVID.


What we know: proximate (short-term) side effects

The crux of the concern over these vaccines is fear of the unknown, so before we can talk about the unknown, we need to be clear on what we do know, as well as clearly defining what we mean by “unknown, long-term effects.”

There are basically two categories of effects we need to talk about:

  • Proximate effects (short-term) = effects that first occur shortly after vaccination
  • Unknown future effects (long-term) = effects that do not show up for months or years after vaccination (Note 1)

It is important to make this distinction, because I often find that people meander back and forth between these two without having a clear understanding of what is actually known or how it is known. So let me try to be as clear as possible: we have an extremely robust understanding of proximate effects, and the fact that the vaccines are new is 100% irrelevant.

Proximate effects are fairly straightforward to test. First, scientists conduct phase 1–3 human trials using a randomized, placebo-controlled approach, where they follow thousands of patients for several weeks following vaccination. Then, once the vaccine is released to the general public, scientists continue to monitor it for side effects using things like large cohort studies and case-controlled studies. As the sample sizes increase, so does our ability to detect increasingly rare events. With tens of thousands of participants, we can detect events that occur every few thousand people, but we will miss events that happen once for every 10,000 people. At a few hundred thousand people, we can detect events that occur once per tens of thousands of people, but will miss events that happen once for every 100,000 people, etc. (Note: numbers are approximations).

There are two critical points here. First, because our ability to detect rare side effects is dependent on sample size, as the sample size increases, any new side effects will, by definition, be increasingly rare. By the time we are into the millions (as we are with COVID vaccines) we aren’t going to suddenly find a new common serious side effect, because those would have been picked up at much smaller sample sizes.

Second, the novelty of the vaccines is completely and totally irrelevant. Because we are talking about events that happen within a few weeks of being vaccinated, it does not matter if the vaccines have been available for two months or two hundred years. The only thing that matters is the sample size (i.e., number of participants). Let me say that again (in bold), our ability to confidently know the rates of proximate side effects depends entirely on the sample size; the age of the vaccine is 100% irrelevant.

In the case of COVID, we were able to get these sample sizes extremely quickly because there were so many cases of COVID and governments dumped so much money into massive vaccine campaigns. All of the currently recommended vaccines passed their initial phase 3 trials with large sample sizes. For example, Pfizer used over 43,000 participants (Polack et al. 2020), and Moderna used over 30,000 (Mahase 2020).

Following those phase 3 trials, numerous large studies have been released. Indeed, so many studies have been conducted that we can do systematic reviews and meta-analyses. As explained here, these combine the data from multiple studies to look for overarching effects and are the highest level of scientific evidence. Qianhui et al. (2021), for example, included 87 different safety studies, and concluded that, “Available evidence indicates that eligible COVID-19 vaccines have an acceptable short-term safety profile.”

Yet more studies have been conducted since that review/meta-analysis, and some of them are truly massive. Barda et al. (2021), for example, compared over 800,000 vaccinated individuals to over 800,000 unvaccinated individuals to look at the rates of adverse events from the Pfizer vaccine as well as the rates of those same events in people who develop COVID. Not only did the vaccine have low rates of serious side effects, but, for most conditions (including myocarditis and myocardial infarction), the rates of those events were higher in people who caught COVID than in people who received vaccines (Note 2).

Figure 4 from Barda et al. 2021 showing the risk of adverse events from the Pfizer vaccine and from COVID itself. For each side effect, risk was calculated by by matching over 100,000 people who had been infected with COVID with people who were not infected with COVID (for COVID side effect rates), and matching several hundred thousand people who had received the vaccine with people who had not received it (for the vaccine rates). In most cases, COVID infection itself carries more risk of these specific side effects than does the vaccine. The most obvious exception (lymphadenopathy) is merely a swelling of the lymph nodes, which is not generally a serious condition.

Figure 4 from Barda et al. 2021 showing the risk of adverse events from the Pfizer vaccine and from COVID itself. For each side effect, risk was calculated by by matching over 100,000 people who had been infected with COVID with people who were not infected with COVID (for COVID side effect rates), and matching several hundred thousand people who had received the vaccine with people who had not received it (for the vaccine rates). In most cases, COVID infection itself carries more risk of these specific side effects than does the vaccine. The most obvious exception (lymphadenopathy) is merely a swelling of the lymph nodes, which is not generally a serious condition.

Other calculations of the rates of specific adverse events have had even large sample sizes. For example, the Israel Ministry of Health used over 5 million people to calculate the rate of myocarditis following vaccination. Similarly, in the USA, the CDC has several hundred million vaccine doses to use in its calculations.

The point is that we are extremely confident about the short-term consequences of the vaccines. It’s hard to overstate the massive volume of data we have. Barda et al. (2021), for example, is one of largest cohort studies I have ever read. It is larger than most studies on the safety of well-established vaccines that have been available for decades. Indeed, we have been able to quickly collect so much data that our knowledge of the short-term safety of COVID vaccines is equal to or greater than our knowledge of the short-term safety of many standard vaccines.

Again, to be 100% clear, the fact that the vaccines are relatively new simply does not matter for these short-term effects. Further, these studies aren’t the result of “rushing.” Rather, it is simply matter of vaccinating so many people so quickly that we were able to rapidly collect the data that would usually take years to accumulate. It is the size and volume of the studies that matters, and we have numerous truly massive studies unequivocally showing that serious side effects are rare and the benefits outweigh the risks.

To put it simply, the short-term side effects of the COVID vaccines have been thoroughly studied and are extremely well-documented. Scientifically, these vaccines are no longer experimental (with the exception of their application to young children, in some cases). They have already passed numerous experiments and the evidence is clear (Pfizer isn’t “experimental” legally either). Insisting that we haven’t studied the vaccines well-enough to know the short-term side effects is, at this stage, science denial.

See Note 3 regarding the supposed vaccine-related deaths and injuries reported in VAERS.


Vaccines don’t cause wide-spread, long-term adverse events

Now we can finally turn our attention specifically to the topic of unknown, long-term effects (which, remember, are effects that do not show up for months or years after vaccination; Note 1). I realize I took a long time getting here, but that background was important, because I have shown that we have a massive body of studies showing that the COVID vaccines have few serious side effects shortly after receiving them. Thus, the only way to doubt their safety without outright science denial is to raise concerns over presently unknown, long-term effects, but, as I will show, those concerns have no scientific merit.

The type of future long-term consequence that everyone seems so afraid of (i.e., the type that only manifests months or years down the road) is virtually unheard of from vaccines. I looked long and hard for examples of this occurring, and in the entire history of vaccines, I was only able to find one: Pandemrix, an H1N1 vaccine used in Europe for the 2009–2010 flu season was associated with an increased risk of narcolepsy that usually only manifested weeks or months after the vaccine. You can read more details on Thoughtscapism and Skeptical Raptor, but there are just three points I want to make.

  1. Depending on the study, the lag between vaccination and onset of narcolepsy was 0-242 days (median = 42; Partinen et al. 2012) or 0-360 days (median not reported; Nohynek et al. 2012). Pfizer and Moderna both began their phase 3 COVID vaccine trials on 27 July 2020 (~400 days ago) and received emergency use authorization (thus starting mass vaccination campaigns in the USA) in December 2020 (~260 days ago). Indeed, Israel had already administered over 1 million doses by the end of 2020. This means we are already past the time frame where we should have started picking up something comparable to the long-term effects of Pandemrix.
  2. As is so often the case with vaccine side effects, the disease they prevent (influenza in this case) also causes the same side effect.
  3. This side effects was rare (between 1 in 52,000 doses and 1 in 57,500 doses in England [Miller et al. 2013] and 1 in 16,000 in Finland [Nohynek et al. 2012; for unclear reasons, Finland had a high rate that could not be generalized to other countries), and the benefits of the vaccine still outweighed the risk.

That last point is really important, because for it to turn out that avoiding the COVID vaccines was the safer choice, unknown future side effects would not only have to exist, but they would have to be so common and so serious that they outweigh the enormous known benefits of the vaccines, and that is a situation that has never occurred for any vaccine (Note 4). For reasons that I’ll explain in the next sections, that’s simply not how vaccines interact with the body.

So, if you are avoiding the COVID vaccines because of a fear of unknown, serious, long-term side effects, ask yourself, is that fear really rational given that future, long-term side effects of vaccines are virtually unheard of, and there has never been a case where those side effects were widespread and outweighed the benefits of the vaccines?


Why vaccines don’t cause future long-term effects: Low dose, short exposure

Let’s now talk about why vaccine side effects nearly always show up shortly after vaccination. The type of long-term consequence we are talking about typically comes from one of two causes: a very large dose over a short time, or a small dose over a prolonged period of time. Vaccines don’t fit either of those categories. They are fundamentally different from most medications because they simply train your immune system before being quickly removed. Your own immune system is what provides a lasting benefit. Further, vaccines do this via low, non-toxic doses. Remember, the dose makes the poison. Everything, even water (Garigan and Ristedt 1999), is toxic at a high enough dose and safe at a low enough dose. So people who scream about “TOXIC CHEMICALS” in vaccines are ignoring basic chemistry. There is no such thing as a toxic chemical, there are only toxic doses, and the doses in vaccines are not toxic.

One of the most common arguments I hear people making to justify concerns over COVID vaccines is, “look at all the examples of drugs that were approved, then years later long-term effects were found.” Those examples are, however, nearly always for drugs that were taken repeatedly. It’s the cumulative effect that causes the risk (particularly for chemicals that persist in your body for long periods of time). Vaccines, in contrast, have limited exposure, and your body quickly eliminates them. Within a few days of receiving the vaccine, the vaccine itself has been totally eliminated from your body. The long-term protection comes from immune system memory, not from the vaccines themselves.

This is really important, because it means we don’t have a mechanism through which COVID vaccines would cause long-term harm. Because vaccines are a low doses given 2-3 times, we expect any consequences to happen quickly, which is exactly what we find. The most common side effects are things like soreness and moderate flu symptoms that start within a few hours or days of receiving the vaccine. These effects aren’t because the vaccine is “toxic” but rather because it is doing exactly what it was designed to do and stimulating your immune system. It’s that activation of your immune system that makes you feel unwell, but that activation is critical, because it is how your immune system learns to identify and fight COVID. Similarly, serious side effects from the vaccines, while rare, usually show up shortly after vaccination.

Side effects that don’t show up for months or years simply aren’t expected from vaccines because of how vaccines work. Nevertheless, in the following sections, let’s look more closely at the three main hypothetical sources of long-term harm: adjuvants/preservatives, mRNA, and immune activation.


#1: Adjuvants and preservatives

Vaccines typical consist of three basic components: a representation of the infectious agent (antigens, weakened viruses, virus particles, mRNA, etc.), an adjuvant that simulates the immune system and/or aids in delivery of the antigen, mRNA, etc., and preservatives (usually salts, metals, and sugars) to avoid contamination and stabilize the other components.

The later two categories (adjuvants and preservatives) are historically the things that anti-vaccers have targeted (e.g., the infamous, and completely false, accusation that thimerosal [ethyl-mercury] caused autism). These accusations have, however, never stood up to scrutiny. Vaccine components have been well-studied and are safe at the doses used in vaccines.

Specifically for COVID vaccines, their components differ from one vaccine to the next, but the safety of the components is well-known. Many of them use standard salts/metals that have been used in numerous previous vaccines and medications, and the non-mRNA vaccines usually use the adjuvants that have already been used in other vaccines.

Specifically for the mRNA vaccines, they use a different type of antigen known as a “lipid nanoparticle” (basically a small, fancy fat) that stimulates the immune system and serves as a delivery mechanism for the mRNA. These are new for a commercially available vaccines (because we’ve never had commercially available mRNA vaccines before), but that doesn’t make the nanoparticles themselves new, and there is a wealth of studies on them (including studies on other vaccines that have been being developed [see previous section on the history of mRNA vaccines]). See Hou et al. (2021) for an extensive review of the topic.

My point is simply that while the vaccines are “new,” their components have been well-studied, and there is simply no reason to think that they pose a long-term danger.


#2: mRNA

Now let’s turn our attention to the big one that has so many people worried: mRNA. At the outset, we need to be clear on what mRNA is and which it does. Your cells contain DNA stored in the nucleus. This provides the plans for your body and how it runs, and it is what you pass on to make your offspring when you procreate. For the actual day-to-day running of your body, however, it has to be transcribed into mRNA (aka “messenger RNA”). This is a single stranded copy of your double-stranded DNA. The mRNA can then leave the nucleus and go to the ribosomes (little protein factories in your cells) which translate the mRNA into amino acids which are then strung together and folded to form proteins. This is happing millions of times in your body each second. Importantly, the process does not alter your DNA. Your genetic code is unaffected. Think of it like taking a master copy of a recipe, photocopying it, then giving that photocopy to someone who then follows the instructions on it.

Viruses are actually pretty neat and replicate by tapping into this system. They can’t reproduce on their own. Instead, they insert their DNA or RNA into your cells and hijack your molecular machinery by making the ribosomes translate their RNA and build new virus (some viruses have DNA and require a transcription step, others [like COVID] store their genetic material as RNA).

The mRNA vaccines tap into this same process. They include a small fragment of the RNA from the SARS-CoV-2 virus (specifically for the spike protein), thus causing your cells to produce that spike protein. Your immune system is then stimulated to attack the spike protein, and in the process, it learns to attack the actual SARS-CoV-2 virus. Take a minute to stop and marvel at the ingenuity of this system, because it’s incredible.

There are several important points that need to be made here:

  1. This process does not alter your DNA. The viral mRNA does not get integrated into your DNA. This is not gene therapy. All that happens is protein production by ribosomes. Again, this is like handing your cells a photocopy of a set of instructions.
  2. mRNA is a very fragile, short-lived molecule. During my PhD, I worked in a laboratory where some people do RNA research, and they often joked that if you looked at the vials the wrong way the RNA would vanish. The point is that the mRNA from the vaccines very quickly breaks down and is removed from your body. Within a few days of receiving the vaccine, it is totally gone.
  3. The vaccines only contain the mRNA for a single protein. It is impossible for them to cause your body to make the full virus. They simply don’t contain that information.
  4. This is a process that is already happening constantly in your body. Right now, you almost certainly have some viruses (even if you are healthy), and those viruses are hijacking your cells with their RNA and forcing your cells to make virus for them. Indeed, unlike with the vaccine, they are making your body produce entire viruses, not just a single protein. Similarly, anytime you become infected with a cold, the flu, etc., your body is exposed to tons of viral RNA which it then translates into proteins (entire viruses)
  5. (related to #4) If you become infected with COVID, this process is going to happen anyway, but unlike with the vaccine, your cells are going to produce the entire virus, and, because the virus will be replicating, you will be exposed to substantially more viral RNA for a longer period of time.

That last point is incredibly important, because it means that any fears you have about the mRNA in the vaccine should be even greater for the virus itself. It doesn’t make any sense to simultaneously downplay the seriousness of COVID while fearing the mRNA in the vaccines, because if you catch COVID, you are going to be exposed to substantially higher doses of viral RNA!

As you can hopefully see, none of this lends credence to the idea that the vaccine will cause long-term effects. There is simply no mechanism through which the mRNA could cause long-term harm, and even if there was a concern over long-term effects, that concern would be even higher from actually catching COVID!


#3. Immune activation

The final way in which vaccines could, in concept, cause harm is as a side effect of the inflammatory immune response they stimulate. Indeed, that is the cause of most vaccine side effects. The vaccine sets off a cascade of immune responses, and sometimes your body gets caught in the crossfire, though this rarely causes serious problems.

Importantly, however, this happens while your immune system is being stimulated. This isn’t a pathway that we would expect to not cause any noticeable problems shortly after vaccination, then suddenly cause massive problems down the road. It could, in concept, cause a problem that starts shortly after vaccination and persists long-term, but it’s unlikely to cause problems that don’t appear until months or years later.

This is important because, again, problems that arise shortly after vaccination and persist aren’t what we are talking about. Those aren’t unknown. Rather, we already know that those are rare because we can detect them shortly after vaccination (see previous section on short-term studies).

Finally, as I’ve alluded to several times already, problems that arise as a result of immune activation should also arise as the result of actual infection with SARS-CoV-2, and they’d usually be expected to be worse or more common from an actual infection. Indeed, that’s exactly what Barda et al. (2021) found.

So, once again, it makes no sense to fear this as a consequence of the vaccine while downplaying the seriousness of COVID, because infection with COVID is more likely to cause this problem (see Note 2 on absolute risk).


How long is long enough?

This is an issue that I’ve written about several times before (e.g., here and here), but in short, the demand for long-term data becomes extremely problematic unless “long-term” is carefully defined and justified beforehand. We already have over a year of data on COVID vaccines, plus many years of data on mRNA vaccines more generally. For most scientists, based on everything we know, that is plenty long enough to be confident in the safety of these vaccines, but if you are going to claim that it is not long enough, the questions become “why?” and “how long is long enough?”

As I said earlier, anti-vacces have used this argument against vaccines for ages, and the problem is that they constantly shift the goal posts. If you show them a 3-year study, they say, “well maybe effects don’t show up until 5 years.” If you show them a 5-year study, they say “well maybe effects don’t show up until 10 years.” If you show them a 10-year study, they switch to 15 years, 20 years, etc. They can keep extending it all the way until the end of the human life-span, and beyond the fact that continually shifting the goal posts is an ad hoc fallacy (and this whole thing is an argument from ignorance fallacy), demanding 15 years of data is only slightly more irrational than demanding 10 years, or even 5 years or 3 years.

Really think about this. Given that no vaccine has ever had a wide-spread, serious side effect that only shows up more than a year after vaccination, what is the justification for demanding 3 years of data instead of accepting the year+ of data we have? How is the demand for 3 years of data more logical than a demand for 10 years, or 20 years, or 60 years? All of those are time categories where we’ve never seen a vaccine suddenly cause new problems and for which we have zero reason to expect these vaccines to cause problems. The probability of a long-term effect only showing up over a year after vaccination is pretty close to zero, which means that it is close to zero for 3 years, 5 years, etc.


Bad risk assessment

As I’ve shown throughout this post, there is simply no good evidence to suggest that the COVID vaccines will have serious long-term consequences that only show up in the future. It’s a baseless fear. Meanwhile, we know that COVID itself is very serious. In the USA alone, it has killed over 650,000 people. In 2020, it was the third leading cause of death in the USA, and in early 2021, it briefly spiked to the #1 slot before dropping back to position #3. We should not be downplaying something that is so prevalent and deadly that it is the third leading cause of death. Further, beyond death, many people suffer serious complications from COVID, some of which will likely persist into the future (Mitrani et al. 2020; Fraser 2020).

Therefore, based on everything we know (which is a lot), risk assessment clearly shows that you are safer with the vaccine than without it, and while it is technically possible that there will be future unknown consequences of the vaccine, these would be even more likely from COVID itself, and it is incredibly unlikely that they will happen from the vaccines and be serious and widespread enough to alter the risk assessment.

By avoiding the vaccine, you are placing more weight on an unknown and unlikely hypothetical future risk than you are placing on a very real and serious known risk.

See the following posts for more details including the “99% survive” argument, precautionary principle argument, and COVID comorbidities


Long-term fears are baseless: The burden of proof

As I’ve explained throughout, there is not one shred of evidence nor a single logical argument that makes it likely that the vaccines will have unknown long-term consequences. This is a completely made-up concern. This isn’t a situation where we have preliminary data suggesting a concern, or a logical/scientific basis for thinking that there is a risk. Rather, this is a concern that was pulled out of thin air with absolutely no evidence behind it.

Further, to be clear, the fact that something is new does not make it likely that there are unknown long-term effects. Indeed, everything we know about vaccines and the immune system makes it extremely unlikely that there will be future, unknown, wide-spread, long-term consequences. Is it technically possible? Sure, but there are an infinite number of technically possible things that will probably never happen. “Technically possible” is not a valid justification for a fear, particularly if that fear will prevent you from taking a medication that greatly lowers your risk of disease and death.

For future unknown consequences to be a logically valid reason for not vaccinating, the probability of serious consequences occurring would need to be high enough to trump the massive known benefits of the vaccines. We would need some really compelling preliminary evidence to suggest that these future injuries will occur, and we simply don’t have it, not one scrap of it.

I say again, this is a made-up concern. Although it makes a certain amount of sense from the standpoint of the psychology of our panicky primate brains, it is a concern that is not based on any evidence or logic. You can’t just make up a concern, then demand action based on that concern. You need actual evidence to support the concern.

In medicine (and science more generally), it is not enough to simply say that something is technically possible. Rather, you have to show that there is a reasonable probability of it being true before it makes sense to treat it seriously (this is something known as the “prior probability”).

Imagine, for example, that I decide that taking aspirin while drinking soda is dangerous, and when asked to justify that fear, I simply say, “well we don’t know that it isn’t dangerous. It’s technically possible that it’s dangerous, and look at how many drugs have been recalled because of some complication with another chemical.”

I think that we can all agree that my fear would be irrational, right? In technical terms, it would be an argument from ignorance fallacy. The fact that something is unknown, doesn’t mean that I can act as if that thing is known to be dangerous. There are an infinite number of things that are unknown. There are an infinite number of potential interactions and long-term effects for all treatments, including vitamins, supplements, herbs, etc.  There haven’t been, for example, any 30-year studies on the effects of regularly taking most vitamins or supplements, and given that those are taken daily, they are far more likely to cause long-term issues. So why not be concerned about them?

Do you see the point that I am getting at here? The fact that we haven’t looked at 3-year effects of the vaccines (or 5 years, or 10 years, etc.) would only matter if we actually had evidence to suggest that there would be problems down the road, and we don’t have that evidence. Indeed, all of the evidence suggests the opposite. Therefore, this is a baseless fear and the burden of proof is on those who are avoiding the vaccine based on these concerns.

Now you could try to quibble with me and say that, “No one is saying that there definitely are long-term effects. We are just saying that we don’t know if there are and, therefore, we should not take the vaccine until we do know.” But, again, that doesn’t work for all the reasons that I’ve laid out. A lack of knowledge simply isn’t sufficient in and of itself. This is an abuse of the precautionary principle, and although you may not be claiming that there are, in fact, long term effects, by choosing to avoid the vaccines, you are, nevertheless, acting as if there will be those effects. As explained earlier, that’s bad risk assessment.

I want to conclude this with some questions. If you are not vaccinating because of concerns over unknown long-term effects, ask yourself, “why do I have those concerns?” Can you point to any actual data to justify them, or is it simply a fear of the unknown? If the latter, ask yourself how likely it is that those fears will come true. The fact that something is new or unknown doesn’t make it dangerous. Given the very real risk of COVID, the decade+ of research on mRNA vaccines, the decades of research on vaccines in general, the massive studies on the COVID vaccines, and the fact that no vaccine has ever had the type of serious, widespread, unknown, long-term side effect that everyone is so afraid of, does it really make rational sense to avoid the vaccines out of fear of the unknown? Does it really seem more likely that you will be injured by this totally hypothetical and unprecedented vaccine injury than by a virus that is currently the 3rd leading cause of death in the USA?



Note 1: When we talk about unknown long-term effects, we are not talking about adverse events that happen shortly after vaccination and continue to cause problems into the future (those are proximate events that have long-term consequences). We aren’t talking about something like myocarditis which, in rare cases, occurs shortly after vaccination and (in a small subset of the most extreme cases) can cause long-term damage. We already know that those events are extremely rare, because we’ve already been able to detect them. They aren’t unknown. In other words, because those events are first detected shortly after vaccination, we have been able to test them with the current short-term studies and have shown that they are extremely rare.

Note 2: Barda et al. (2021) was comparing rates among the vaccinated with rates among the infected, not absolute risk. Absolute risk depends on how likely you are to become infected. However, other analyses (e.g., Gargano et al. 2021) have shown that in high-risk countries like the USA, your absolute risk of serious injury and death is lower with the vaccine than without it, even if you are in a low-risk COVID group.

Note 3: There are many false claims floating around about thousands of deaths following vaccination. These claims are based on VAERS which includes anything observed following vaccination and does not establish causation. With millions of people receiving vaccines, it is inevitable that a few thousand will die shortly afterwards just by chance. In the vast majority of cases, there is simply no reason to think that the vaccines were responsible. Similarly, while some of the adverse events reported in VAERS may have been caused by vaccines, most probably weren’t. The database is self-reported (anyone can make entries), and some truly wacky submissions have been included. Further, again, the fact that something happened after vaccination absolutely does not mean that the vaccine caused it (that’s a post hoc ergo propter hoc fallacy; more details here and here). To quote the CDC “FDA requires healthcare providers to report any death after COVID-19 vaccination to VAERS, even if it’s unclear whether the vaccine was the cause. Reports of adverse events to VAERS following vaccination, including deaths, do not necessarily mean that a vaccine caused a health problem. A review of available clinical information, including death certificates, autopsy, and medical records, has not established a causal link to COVID-19 vaccines” (the bold was in the original). More details on VAERS here.

Note 4: Again, to be 100% clear, we are talking about injuries that won’t show up until later down the road. You certainly can find examples from decades ago where there were issues with a vaccine rollout (particularly concerning polio vaccines), but those issues were immediate, and that’s not what we are talking about here. The COVID vaccines all underwent massive randomized controlled trials and have been carefully monitored following release to the public, and with the hundreds of millions of doses that we have administered, we have a very clear picture of the immediate risks and benefits. Those aren’t unknowns.


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