Two of the most persistent anti-vaccine tropes are that unvaccinated children are healthier than vaccinated children and that “natural” immunity is better than “artificial” immunity. There has never been any evidence to support these claims, and plenty of evidence that they are wrong (Schmitz et al. 2011; Grabenhenrich et al. 2014), but two recent studies have shed new light on just how wrong they are. These studies built on previous work and showed that infection with the measles virus actually destroys memory cells, resulting in “immune amnesia” for years to come. In other words, becoming infected with measles makes you far more likely to be infected with other diseases for several years after the original measles infection. It actually weakens your immune system, rather than building it.
Before I can talk about these studies and their implications, I need to briefly explain how the immune system and vaccines work. I have done so in more detail here, so I’ll be brief. When a pathogen first enters your body, it is attacked by the innate immune system, which provides a non-specific response. In other words, it does not have specific cells for fighting specific pathogens. While this is happening, however, your adaptive (aka acquired) immune system goes into action. This immune system is more specific and generates T and B cells (specialized immune cells) that are specific for targeting a particular pathogen. This is a very powerful arm of your body’s immune defenses and is vital for fighting things like measles infections. It takes time, however, for your body to learn to recognize a new pathogen and build appropriate cells and subsequent antibodies to respond to it. While this is happening, the pathogen multiplies, and you become sick.
After the infection (assuming you survived). Your body maintains memory T and B cells for that pathogen so that it can respond quickly in the future. Your body also retains antibodies from the initial infection which can respond immediately to future infections by that pathogen. This is how natural immunity works.
Vaccines activate the same system, but do so by presenting your body with the antigens (proteins your body uses to recognize pathogens) for the pathogen in question (or a dead or weakened version of the pathogen) rather than giving you the live, healthy pathogen. This causes your body to go through the same cycle of producing B and T cells and releasing antibodies that it would go through for a real infection, but there is one critical difference: you don’t get the disease. This is the fundamental reason why it is absurd to argue that natural immunity is better than artificial immunity. To get natural immunity, you first have to get the disease! It is literally arguing that it is better to get the disease so that you don’t get it again rather than just never getting it in the first place!
But what about the claim that getting a disease helps build the immune system? As you can hopefully now see, it only “builds” the immune system in that it teaches the body how to respond to one particular pathogen, which is exactly what vaccines do without ever making you sick. There is, however, another catch here, which is where the new studies come in. As it turns out, while measles infections are “building” the immune system by teaching it how to respond to the measles virus, they are also destroying memory cells and greatly weakening the immune system. You see, immunity can be lost. This is true for both natural immunity from infections and artificial immunity from vaccines (though the latter can be easily remedied with boosters). Over time, memory B cells and T cells die, and the number of antibodies circulating in your body for a particular pathogen diminish. This can eventually lead to a loss of immunity. This also means that, in concept, a pathogen could destroy existing immune cells and make you vulnerable to diseases that you were previously protected against. We now know that this is exactly what the measles virus does.
We’ve known for a long time that measles virus infections have a suppressive effect on the immune system, andt5hat suppression is partially why secondary infections are so common for measles patients. This knowledge goes back at least as far as 1908 (Pirquet 1908) and has been corroborated by more recent research (Griffin 2010; de Vries et al. 2012), but what we didn’t realize was just how severe this suppression was or how long it lasted for. Several studies on mice found that viral infections could actually take out previously existing memory cells and, presumably, put the mice at risk for future infections (Selin 1996; Kim and Welsh. 2004), but, as regular readers of this blog know, animal studies are useful starting points, but they only go so far, and we really need studies on humans to get a clear picture of the situation.
Compelling epidemiological evidence of measles having a lasting impact on human immune systems arrived in 2015, when researchers found that measles infections increased mortalities from other infections for 2–3 years after the measles infection (Mina et al. 2015)! This result was corroborated by a large cohort study (one of the most powerful study designs) that found increased infection rates for diseases (other than measles) for five years following infection with measles (Gadroen et al. 2018). These studies provided really good evidence that measles did something harmful to the immune system, but we still weren’t quite sure what it was doing.
This brings us finally to the two recent studies: Petrva et al. (2019) and Mina et al. (2019). Both of these studies took blood samples from children before and after natural infection with the measles virus, and Petrva et al. looked at the effect on B cells, while Mina et al. looked at the effect on circulating antibodies. They both found the same thing: the measles virus reduced the diversity of the immune system (B cells or antibodies) thus putting patients at risk for other diseases. In other words, the virus destroys the components of your immune system that had previously learned to respond to other diseases. Thus, the natural immunity you had to those diseases is gone (or at least greatly diminished) and you are susceptible to them again. Further, this impact was not small. Mina et al found that severe measles infections caused children to lose 11–62% (median = 40%) of their existing antibody repertoire! That’s a huge loss.
Now, you may be wondering what affect the vaccine has. Does it suppress the immune system like an actual infection does? Mina et al. (2019) looked at this as well, and no, it doesn’t. All that it does is make children immune to measles. That’s it. This makes good sense if you understand what is going on here. The measles virus actually infects cells (including memory B and T cells), which is why it can do so much damage to you and your immune system. Vaccines don’t do that. They can’t infect anything because the either don’t contain the pathogen at all, or contain a dead or weakened version of it that can’t infect you. Thus, all that they do is teach your immune system how to respond to a pathogen without any of the damaging effects of actually becoming infected with the pathogen.
Before concluding this post, I also want to point out that another common anti-vaccine myth is that natural immunity is lifelong, whereas artificial immunity is temporary. The papers discussed in the post very clearly show that natural immunity can also be temporary and acquiring natural immunity for one disease can actually cost you previous immunity to others. Further, vaccine-induced immunity often lasts just as long as natural immunity (Jokinen et al. 2007), and even in cases where natural immunity does last longer, it is often not life-long (Wendelboe et al. 2005), and, again, the vaccine prevents you from ever getting the disease in the first place (and their protection can be extended with boosters).
In short, the notion that unvaccinated children are healthier than vaccinated children is not only wrong, it is backwards. Recent research shows that diseases like measles actually do a lot of damage to your immune system and rob you of immunity you had previously acquired to other diseases. This puts you at risk for a wide range of diseases beyond the one that the vaccine protects against. In other words, not only does “natural” immunity to diseases like measles require you to actually get the disease before you can be protected against it, but it also weakens your immune system and makes you susceptible to many other diseases. Vaccines save lives and keep you healthy. It’s that simple.
Rebuttal to a popular anti-vaccine article on this topic
- More anti-vaccine cherry-picking: A rebuttal to, “Should you be afraid that measles can give you immune amnesia?”
- 100 bad arguments against vaccines
- Vaccines and autism: A thorough review of the evidence (2019 update)
- Vaccines don’t “bypass the immune system”
- Vaccines don’t give lifelong immunity, but they are still better than natural immunity
- Vaccine injuries and confirmation biases
- Why are there so many reports of autism following vaccination? A mathematical assessment
- Yes, vaccines did save us from disease: a graphic analysis
- Grabenhenrich et al. 2014. Early-life determinants of asthma from birth to age 20 years: a German birth cohort study. Journal of Allergy and Clinical Immunology 133:979–988.
- Gadroen et al. 2018. Impact and longevity of measles-associated immune suppression: a matched cohort study using data from the THIN general practice database in the UK. BMJ 8
- Griffin, DE. 2010. Measles virus-induced suppression of immune responses. Immunol. Rev. 236: 176–189
- Jokinen et al. 2007. Cellular Immunity to Mumps Virus in Young Adults 21 Years after Measles-Mumps-Rubella Vaccination. Journal of Infectious Diseases 196: 861–867.
- Kim and Welsh. 2004. Comprehensive early and lasting loss of memory CD8 T cells and functional memory during acute and persistent viral infections. J. Immunol. 172: 3139–3150
- Mina et al. 2015. Long-lasting measles-induced immunomodulation increases overall childhood infectious disease mortality. Science 348: 694–699.
- Mina et al. 2019. Measles virus infection diminishes preexisting antibodies that offer protection from other pathogens. Science 366:599–606
- Petrva et al. 2019. Incomplete genetic reconstitution of B cell pools contributes to prolonged immunosuppression after measles. Science Immunology 4: eaay6125
- Pirquet, C. 1908. Das Verhalten der kutanen Tuberkulinreaktion während der Masern. Dtsch. Med. Wochenschr. 34:1297–1300.
- Schmitz et al. 2011. Vaccination status and health in children and adolescents. Medicine 108:99–104.
- Selin 1996. Reduction of otherwise remarkably stable virus-specific cytotoxic T lymphocyte memory by heterologous viral infections. J. Exp. Med. 183: 2489–2499
- de Vries et al. 2012. Measles immune suppression: Lessons from the macaque model. PLOS Pathog. 8: e1002885.
- Wendelboe et al. 2005. Duration of Immunity Against Pertussis After Natural Infection or Vaccination. Pediatric Infectious Disease Journal 24: S58–S61.