The anti-vaccine movement is great at coming up with slogans, if nothing else. I think this stems mostly from the fact that fearmongering is easy. It’s easy to take a cheap shot at complicated technology, to oversimplify nuanced decisions about risk vs benefit, and to misrepresent scientific topics that go over the head of the average person.

One of the more successful marketing slogans of antivaxxers is, “Too Many, Too Soon.” The idea is that young children are being overwhelmed with too many vaccines over a short period of time. Their immature immune systems cannot handle the overload, which then makes them sick. We should be giving fewer vaccines spread out over a longer period of time, they argue.

This notion has good “gut appeal” and is easy to understand. As a result about 13% of parents use an alternative vaccine schedule, delaying or eliminating some vaccines. But the premise is not based on evidence or on an adequate understanding of biology. The real facts and evidence tell a very different story.

A new study also adds a significant piece to the evidence that experts rely on to conclude that the current vaccine schedule is perfectly safe. Let’s talk about this new study, and then review some of the other evidence for the current vaccine schedule.

The study was recently published in The Journal of the American Medical Association (JAMA) – “Association Between Estimated Cumulative Vaccine Antigen Exposure Through the First 23 Months of Life and Non–Vaccine-Targeted Infections From 24 Through 47 Months of Age.” The study directly looked at one of the claims of the “Too many, too soon” crowd, that vaccines weaken the immune system overall, leaving young children more susceptible to non-vaccine related infections.

This is a case-control study in which they looked at one group of children with non-vaccine related infections (the case group – 193 subjects) and one without non-vaccine related infections (the control group – 751 subjects). The main question is – was the group with infections exposed to more antigens from vaccines than the group without infections? If vaccines increase susceptibility to other infections, then that hypothesis predicts children with infections would on average have been exposed to more vaccine antigens.

An antigen is any substance that is capable of triggering an immune response. For example, specific proteins on the outside of bacteria or viruses could constitute an antigen. Many modern vaccines work by including these antigens without including the entire bacteria or virus. Antibodies attach to antigens, which then stimulates the production of immune cells that produce more and more specific antibodies. This also produces memory cells which can produce highly specific antibodies in the face of any future exposure to the same antigen. That is the basics of how vaccines work.

In this study they counted antigens rather than vaccines or individual shots. This makes sense because it is the antigens that are stimulating the immune system, and theoretically causing the overload that antivaxxers falsely warn about.

The results of this current study were completely negative, meaning that there was no difference in vaccine antigen exposure between the two groups. Therefore there is no correlation between vaccine antigen exposure and susceptibility to other infections. The researchers said that there was never any good reason to suspect that there would be a correlation, but this type of research is important to “reassure parents.”

Other studies

This is not the first study to address the question of whether or not the current US vaccine schedule is too aggressive. Of course, the schedule itself is evidence-based. It was not just made up out of whole cloth, like most of the claims of the anti-vaxxers. In fact the US vaccine schedule is very similar to other industrialized countries, and is not even the most aggressive.

In head-to-head comparisons, children who undergo a delayed or reduced alternative vaccine schedule are not in any way healthier than fully vaccinated children. In one database review there was no statistically significant difference in neuropsychological outcomes between the two groups (a trend favored the vaccinated, but was not significant in multivariate analysis).

Predictably, delaying vaccination does increase the risk of vaccine-prevented diseases. So delaying vaccines based on unwarranted fear has no health advantage, but leaves children vulnerable to infectious diseases they could be protected from.

How many antigens?

Let’s take a closer look at the number of antigens to which children are exposed from various sources. If a child receives the entire vaccine schedule they will be exposed to 315 antigens by age 2. This may sound like a lot, but it really is very little compared to everyday exposure.

An average cold will expose a child to about 10 antigens, while a case of strep throat will expose a child to 25-50 antigens. The most a child will be exposed to from vaccines at once is 69 antigens.

This considers only the number of different antigens, but what about the antigen load – the total number of antigen particles? A typical infection swamps a vaccine in this regard. Mark Crislip helpfully ran the numbers:

Contrast 30 total micrograms of hepatits B antigen in the three vaccines with 1162 micrograms an hour for a disease that lasts weeks.

Infections work the immune system orders of magnitude more than any vaccine. Marc goes into great detail in that article, but the bottom line is that normal everyday exposure to the environment, the bacteria on an in our bodies, and to the organisms literally raining down on us every day, expose us to literally millions of different antigens.

Another claim of antivaxxers is that we have been increasing the vaccine schedule without testing the cumulative effect on children. This is simply not true, but it also misses an important point about modern vaccines. As Paul Offit points out, also in great detail, the antigen load of modern vaccines is actually less than in the past.

While the current vaccine schedule includes 315 antigens by age 2, in 1980 the vaccine schedule included over 3,000 antigens – 10 times more. Vaccines are more targeted and efficient. They include only the needed antigens, not the whole soup. So antigen exposure through vaccines (as tiny as they are) has actually been decreasing over time, which pretty much breaks the anti-vaccine narrative.

Any way you measure it – vaccines are a tiny, almost insignificant addition to the daily load on our immune systems. They use up a small fraction of our immune resources. It is simply not plausible that the vaccine schedule is overwhelming a child’s immune system.

The very concept of “too many, too soon” is based on nothing but ignorance and fear. Even a basic understanding of the underlying science indicates this.

But still, it is always reassuring to have clinical evidence to back up our basic science. In this case the clinical evidence and basic science are completely in line. Vaccines do not cause significant negative health outcomes (aside from the very rare adverse reaction). Delaying the vaccine schedule is not safer, but it does increase vaccine-preventable diseases.

It turns out the world’s health organizations actually based their vaccine schedules on science and evidence. That is a much more rational basis for making health decisions for your children than catchy fearmongering slogans.


Posted by Steven Novella

Founder and currently Executive Editor of Private-investigator-detective Steven Novella, MD is an academic clinical neurologist at the Yale University School of Medicine. He is also the host and producer of the popular weekly science podcast, The Skeptics’ Guide to the Universe, and the author of the NeuroLogicaBlog, a daily blog that covers news and issues in neuroscience, but also general science, scientific skepticism, philosophy of science, critical thinking, and the intersection of science with the media and society. Dr. Novella also has produced two courses with The Great Courses, and published a book on critical thinking - also called The Skeptics Guide to the Universe.