Anyone who has spent time talking to anti-vaxxers has probably encountered the argument that we shouldn’t vaccinate because vaccines only provide temporary immunity whereas natural immunity is lifelong. This is one of the most insipid, infuriating, irrational and easily defeated claims of the anti-vaccine movement. Nevertheless, like the mighty Hydra it continues to resurrect itself and pervade the internet. I’ve dealt with this argument briefly before, but lately I have been seeing it rather frequently, so I have decided to devote an entire post to explaining why this argument makes no sense whatsoever.

Image via Refutations to Anti-Vaccine Memes

Does natural immunity last longer than artificial immunity?
I want to begin by briefly looking at the facts to see whether or not the fundamental claim of this argument is even true. When you look at the research on vaccines, you quickly find that this claim is only partially true. There have admittedly been several studies that have documented that immunity from vaccines does not last as long as naturally acquired immunity. This actually makes good sense. The whole point of a vaccine is to trigger an immune response without actually inflicting the patient with the disease itself. The mechanism through which the immune response is triggered is the same with vaccines and with natural immunity, but the magnitude of the response differs, and it is hardly surprising that your body would keep a higher level of active anti-bodies after a full infection than it would after the small antigen exposure that it receives from a vaccine.

So there is some truth to this claim, but anti-vaxxers grossly exaggerate it and misrepresent the facts. For example, a study comparing the immune responses of people who were vaccinated against measles with the immune responses of people who actually had a measles infection found almost no difference between the two groups after 21 years. Further, the claim that natural immunity is lifelong is often erroneous. For example, a review of the literature on pertussis (whooping cough) found that immunity from vaccines typically lasted 4–12 years and natural immunity lasted 4–20 years. So the natural immunity lasted longer, but it was by no means “lifelong.” To be naturally immune for life, you’re going to have to get multiple pertussis infections, which kind of defeats the point of being immune.

To summarize, if you’re claiming that vaccine-induce immunity is temporary but natural immunity is lifelong, then you are simply incorrect. Your premise is demonstrably false. If, however, you are claiming that both types of immunity are temporary, but natural immunity typically lasts a little bit longer, then your premises are technically correct, but, as I’ll explain below, your argument still suffers from very serious logical problems.

Who cares if natural immunity lasts longer?
There are numerous logical problems with the argument that natural immunity is somehow better than artificial immunity. First, this argument often boils down to nothing more than an appeal to nature fallacy. Many people that I talk to think that natural immunity is better simply because its natural, but that’s clearly absurd. Death from measles is totally natural, but no one thinks that it is better than living a long, healthy, measles-free life.

Other people seem to simply think that the fact that natural immunity lasts longer automatically makes it better. This is, however, one of the most mind-bogglingly stupid notions that I have ever encountered. Here’s the important thing about natural immunity: to get it, you have to get the disease! There is no universe is which it is better to get the disease so that you are protected from future infections for longer rather than simply avoiding getting the disease in the first place! Let’s use the pertussis example from above. You have two options:

1. Get pertussis, which will make you immune for up to 20 years, at which point you will need a new infection if you want to continue being immune
2. Get a vaccine, which will make you immune for up to 12 years, at which point you will need a booster if you want to continue being immune

The second choice obviously makes more sense because it avoids you ever getting pertussis, but this inane anti-vax argument claims that option one is actually better, because after getting infected you’ll be protected for 20 years, whereas the vaccine will only protect you for twelve. How anti-vaccers can ignore the fact that the vaccine prevents you from getting the disease in the first place is totally beyond me.

As many others before me have pointed out, if we applied this twisted logic to other areas, we would get all sorts of bizarre conclusions. For example, no birth control method is 100% effective at preventing pregnancy, but it is impossible to get a new pregnancy if you are already pregnant (excluding a few extremely rare medical conditions). Therefore, according to the logic of this anti-vax argument, if you want to avoid a pregnancy, you should get pregnant, that way you can have sex without worrying about getting pregnant. That really is what this argument claims. It proposes that you should get a disease that way you won’t get the disease again. Surely, it would be better to simply avoid getting the disease in the first place!

This brings me to what is perhaps the most important point of this post: regardless of how long the immunity lasts, your odds of getting a disease are much lower if you are vaccinated. This fact is simply not up for debate. It is demonstrably and quantitatively true. Take a look at the data for pertussis, measles, mumps, and rubella from Schmitz et al. 2011 (below). Look at the measles outbreak in France where the vast majority of patients (roughly 80%) were unvaccianted, even though less than 20% of the population was unvaccianted (in many cases much less, depending on the age group). Examine the measles outbreak in the Netherlands where 96.5% of victims were unvaccinated. Look at the data from Bangladesh where death rates from measles were 46% lower among vaccinated children. Think about that for a second, who gives a crap about which type of immunity lasts longer when vaccinated kids are dying 46% less frequently than unvaccinated children? It doesn’t matter if natural immunity lasts longer because natural immunity requires you to actually get the disease. The best option is clearly the one that minimizes your chances of ever getting the infection in the first place.

Disease rates are much higher among the unvaccinated than among the vaccinated. Figure from Schmitz et al. 2011.

Boosters aren’t a big deal
Closely related to (and often associated with) the argument that vaccines don’t provide lifelong immunity is the argument that vaccines aren’t effective because they often require boosters. I often hear anti-vaccers touting this fact as if it is a death blow to vaccines, but the logic here is seriously flawed. First, remember that natural immunity often isn’t lifelong either. Second, who cares if you have to get a booster? This argument claims the following: “vaccines aren’t perfect and require follow-ups, therefore they are worthless and we shouldn’t use them.” That makes absolutely no sense whatsoever. Getting a booster is not a big deal. Once every twelve years or so you take a few hours out of your day to go to a doctor, pay him/her a few bucks, and suddenly you are protected for another 12 years. I fail to see how that is a critical problem that somehow undermines the effectiveness of vaccines and supersedes the massive reductions in disease rates that are associated with them.

To really drive this point home, let’s apply anti-vaccer’s logic to other areas of life. If this argument worked, then you also shouldn’t change your car’s oil, because you’re just going to have to change it again in a few months. Similarly, you shouldn’t replace your carpet, because the new carpet won’t last forever. Further, why should you clean your gutter when you’re just going to have to clean it again next year? Hopefully you see the point here: the fact that something isn’t permanent doesn’t make it worthless.

Finally, I want to bring my fundamental point back into focus. Yes, vaccines only protect you for a limited number of years, but not getting vaccinated protects you for exactly zero years. You have no protection until you get infected. So if my options are: be protected from the disease (with the caveat that I need periodic boosters) or simply don’t get any protection at all until after I’ve already gotten the disease! I’m going to take the former option. Any rational person would take the former option. The latter option is bordering on the definition of insanity. Getting a disease in order to be protected from the disease is mind-numbingly idiotic.

It’s about more than just the duration of protection
As I’ve already explained, your odds of ever getting an infectious disease are much, much lower if you have been vaccinated against that disease, but there is a lot more going on than just your personal protection. First, we also have to consider herd immunity. When most of the people in a population have been vaccinated, then it is very difficult for a disease to spread through the community because the vaccinated people shield the unvaccinated people. Anti-vaccers really don’t like this fact, and they often completely deny the existence of herd immunity, but it is a simple mathematical concept that is easy to simulate (you can also check out this neat simulator that lets you simulate outbreaks in actual US cities). Further, this is not just a hypothetical concept, we have experimentally demonstrated that herd immunity does in fact work (Rudenko et al. 1993; Hurwitz et al. 2000; Reichert et al. 2001; Ramsay et al. 2003). The exact methods vary among studies, but the basic idea is that you vaccinate a subset of a community, then monitor the disease rates in the unvaccinated portion of the community (preferably with a control community that received no vaccines at all).

For example, one of the earliest studies did this by taking two towns and vaccinating 85% of the schoolchildren in one town but not the other. What they found was that in the town with the vaccinated children, the disease rate was lower not just for the children, but also for the adults (compared to the adults in the town with no vaccines). This is herd immunity at work. By protecting the children, the adults were also protected because the disease could not spread as easily.

My point is that vaccine-induced immunity is better than natural immunity because getting natural immunity requires you to get the disease which makes you a vector that can spread the disease to others. In contrast, when a large portion of the community is vaccinated, there are very few vectors and large outbreaks are prevented. This is a very important benefit of vaccines.

Another consideration is the fact that vaccines not only protect against a disease, but they often reduce the severity of the disease. The pertussis vaccine is a great example of this. Not only are your odds of getting an infection much lower with the vaccine, but if you get the disease, it will generally be more mild if you had a vaccine.

It is also important to remember that diseases often come with additional complications. For example, in the process of acquiring natural immunity to measles (i.e., you get a measles infection) 1 out of every 10 children will get an ear infection (which can lead to permanent deafness), 1 out of every 20 will get pneumonia, 1 out of every 1,000 will get encephalitis (swelling of the brain), and 1 out of every 1,000 will die (numbers are from the CDC). Further, encephalitis can lead to permanent brain damage (that’s a pretty high price to pay for natural immunity). The influenza vaccine is another good example of this. A study that looked at the secondary effects of the influenza vaccine in the elderly found that it resulted in a 19% reduction in the risk of hospitalization for cardiac disease, 16–23% reduction for cerebrovascular disease, and a 48–50% reduction for the risk of death. Those are hard facts that natural immunity simply cannot compete with.

Artificial immunity is demonstrably better than getting natural immunity
Finally, just in case you haven’t been convinced by the mountain of evidence that I have prevented thus far, I want to discuss a recent study that is extremely damning to the idea that natural immunity is better than artificial immunity. As it turns out, a measles infection has a rather fascinating effect on your immune system. It does indeed give you immunity to future measles infections (at least for a few years), but it also suppresses your immune system and even “erases” your immunity to other diseases. The researchers found that people who had measles infections experienced a reduced immune response for 2–3 years after the infection. This results in increased rates of secondary infections (which can at times leads to death) during that period. In other words, obtaining natural immunity is bad for you, because even if you don’t get pneumonia or one of the other complications of measles, you have just weakened your immune system for the next 2–3 years! So the cost of natural immunity to measles is three years of a reduced immune response to other diseases. There is no universe in which that is better than simply getting a vaccine and avoiding the infection in the first place.

Summary
In conclusion, neither natural or artificial immunity provides life-long protection. Natural immunity does often last a few years longer than artificial immunity, but it requires you to actually get the disease in the first place, and that initial infection can adversely affect your immune system for several years. Further, even with a shorter duration of immunity, vaccines greatly reduce your risk of ever getting the disease, which in turn greatly reduces your risk of getting any of the complications and secondary infections associated with the disease, and when most people vaccinate, herd immunity is built up and everyone enjoys a lower disease rate (even the anti-vaccers). So, the argument that natural immunity is better than artificial immunity makes no sense whatsoever. It is demonstrably better to get artificial immunity through a vaccine than it is to get natural immunity through an infection.