I wrote recently that HHS Secretary Robert F Kennedy stated that there are too many vaccines given to children — the anti-vaccine community has long stated that this harms the immune system of children.

Yes, we administer more vaccinations today than we did in 1986, but we protect children against more diseases today than we did 40 years ago. That’s a good thing. In 1986, we had childhood vaccines for only seven diseases. In 2025, we will protect against 17 different diseases with vaccines. Again, that’s a good thing.

As I wrote previously, children received over 3000 antigens in vaccines in 1986, but they receive fewer than 200 antigens today. Once again, that’s a good thing — children are protected against more diseases with fewer antigens.

This post will debunk the myth that too many vaccines cause harm to a child’s immune system. The immune system of children and adults is quite robust and is not harmed by a few vaccines.

Multiple vaccines harm the immune system – the myth

The basis of this myth is that there are numerous vaccinations given to children. The meme above, pushed by a lot of vaccine denialists, seems to indicate that the number of vaccines has increased over the years, and as I discussed above, it has. The 2025 CDC recommended vaccine schedule actually states that between 34 and 41 vaccinations are given to children six years of age and younger, depending on the child.

There are even some anti-vaccine activists who use larger numbers for vaccines by counting the number of antigens in each vaccine. For example, they may consider that a quadrivalent flu vaccine counts as four shots.

From this “multiple vaccines harm children” myth, it branches into a lot of sub-myths. One is based on a claim about the scary toxins in the vaccines, and the kids are getting more of them with all of the scary vaccines. This is not an issue

But the bigger sub-myth is that multiple vaccines somehow damage the immune system, because “that’s too many antigens for the young child’s immune system.” They make claims that these excess vaccines “use up” the immune system (yes, use up). Or that because vaccines aren’t natural, they mess up the immune system.

This trope about the immune system contradicts what we know about the immune system. If I could make just one scientific claim, it’s that the immune system, even of children, is powerful, robust, and complex. Our immune system is the result of a hundred million years of mammalian evolution and millions of years of human evolution, which has protected our species from billions of different bacteria and viruses.

Multiple vaccines harm the immune system – the science

If you’re worried about too many vaccines, here’s what the experts say:

• Do Children Get Too Many Immunizations? The Answer is No, Mark Crislip — “Delaying vaccines increases the time during which children are susceptible to certain diseases, some of which are still fairly common. Chickenpox, whooping cough, influenza, and pneumococcus still cause hospitalizations and deaths in previously healthy children. Spacing out or separating vaccines will also require more doctor visits, which will increase overall costs as well as the number of times the children must experience any associated discomfort and stress.”
• The Problem With Dr Bob’s Alternative Vaccine Schedule, Paul A. Offit, MD Charlotte A. Moser, BS — “At the heart of the problem with Sears’ schedules is the fact that, at the very least, they will increase the time during which children are susceptible to vaccine-preventable diseases. If more parents insist on Sears’ vaccine schedules, then fewer children will be protected, with the inevitable consequence of continued or worsening outbreaks of vaccine-preventable diseases. In an effort to protect children from harm, Sears’ book will likely put more in harm’s way.” (Note: this is in reference to Dr. Bob Sears, who used to promote an “alternative” vaccine schedule because there are too many vaccines, but after too many run-ins with the Medical Board of California, he may be staying away from pushing false vaccine information.)
• Alternative Vaccination Schedules, Mark Crislip (Science Based Medicine) — “The preponderance of information in the medical literature on vaccinations is as clear as any topic in medicine. Vaccines are effective and they are safe. The best bet for keeping your child, and your community, healthy is to get vaccinated and to do it on schedule. There are people who see the issue differently, and is often the case, the reasons are more subtle and complicated that one would except. And there is still much to be understood as to why people do and do not participate in the vaccination schedule.”

Let’s take a look at what actually happens in the real world with children’s immune systems. In other words, what does a few vaccines matter in the scheme of all the possible antigens a child encounters during their young life?

In this paper, researchers discovered that:

• In each cubic meter of air, there are between 1.6 million and 40 million viruses.
• In each cubic meter of air, there are between 860,000 and 11 million bacteria.

A child inhales about 5 liters of air per minute (or about .005 cubic meters), so an infant inhales a few hundred thousand viruses and bacteria every minute of every day of the year. Moreover, the researchers discovered that many were unknown species of viruses and bacteria, so the immune system has to adapt to them with each breath.

Thus, the 34-41 vaccinations and 200 or so antigens are not even a significant number compared to the millions upon millions of viral and bacterial antigens that enter a child’s lungs every day or week. The tiny number of antigens introduced by vaccines barely registers on the immune system’s massive and robust power to deal with antigens.

The anti-vaccine world fails to realize the incredible power of the immune system. It “memorizes” literally billions, if not a 1000 times more, of antigens that could cause harm to the infant.

The handful of antigens introduced by vaccines is critical because those antigens are from dangerous pathogens – the immune system just adds that information about these pathogens into its memory bank, it doesn’t get overwhelmed by it.

The complicated and powerful immune system doesn’t get weakened by the “knowledge” from the vaccines. It just moves on to the next antigen, one of the few million that it sees every day.

The immune system does not get weaker unless the child has a chronic disease or malnutrition. You can’t make it stronger, but vaccines cause it to adapt to that particular antigen, so that it “remembers” what to do the next time it encounters that antigen.

Summary

This is easy. Vaccines simply cause the development of adaptive immunity to a pathogen or antigen. This is something that happens a million times a day in a healthy child, teenager, and adult.

As Paul Offit summarized in his landmark paper about multiple vaccines:

Current studies do not support the hypothesis that multiple vaccines overwhelm, weaken, or “use up” the immune system. On the contrary, young infants have an enormous capacity to respond to multiple vaccines, as well as to the many other challenges present in the environment. By providing protection against a number of bacterial and viral pathogens, vaccines prevent the “weakening” of the immune system and consequent secondary bacterial infections occasionally caused by natural infection.

So, more evidence that vaccines do not do what vaccine deniers claim they do. And they do precisely what scientists think they do–save lives.

So, do multiple vaccinations overwhelm the immune system? That’s definitely a myth unsupported by real science.

Citations

• Offit PA, Moser CA. The problem with Dr Bob’s alternative vaccine schedule. Pediatrics. 2009 Jan;123(1):e164-9. doi: 10.1542/peds.2008-2189. Review. PubMed PMID: 19117838.
• Offit PA, Quarles J, Gerber MA, Hackett CJ, Marcuse EK, Kollman TR, Gellin BG, Landry S. Addressing parents’ concerns: do multiple vaccines overwhelm or weaken the infant’s immune system? Pediatrics. 2002 Jan;109(1):124-9. Review. PubMed PMID: 11773551.
• Whon TW, Kim MS, Roh SW, Shin NR, Lee HW, Bae JW. Metagenomic characterization of airborne viral DNA diversity in the near-surface atmosphere. J Virol. 2012 Aug;86(15):8221-31. doi: 10.1128/JVI.00293-12. Epub 2012 May 23. PMID: 22623790; PMCID: PMC3421691.

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