Sensible decision-making about vaccinations

Should you vaccinate your children or not? That's the common question, but it's not the right question. Every disease is different, and if you are thinking about whether to vaccinate you should inform yourself about the risks of each disease and of each vaccine and make your decisions independently.

The standard scenario

When a serious disease is common, everyone wants to vaccinate. While there might be some danger to the vaccination, the danger of the disease is more serious and very clear. But when the vaccination program is successful and the disease becomes rare, then people worry that the risks of the vaccination are worse than the risks of the disease, and some people stop vaccinating.

There are really two versions of this idea. In one case, the parents think that no one should be vaccinating, because the vaccination has eradicated the disease. In the other, the parents feel that, given that most other people are vaccinating, the risks to their own child are less by not vaccinating. In the rest of this document I will discuss only the facts of the situation, and only mention briefly here that this choice puts you in the morally questionable position of being a "free rider": you profit from the risks that others are taking and that you are not willing to take yourself.

Evaluating risks

To make a sensible decision about whether to give your child a specific vaccine you have to understand the dangers of the disease and the dangers of the vaccine. The risks due to the disease are of course first the risk of catching it and then the seriousness of the disease when you have it. It's important to guard against the belief that your children have no chance of getting a disease merely because its incidence of has been reduced by vaccination and it is no longer so common.

The risks of a vaccine are harder to determine than the risks of a disease. Children are vaccinated and then a tiny number of them develop some problem. Is the problem caused by the vaccination? It's hard to tell, because unvaccinated children also develop problems. Only a very careful study of the incidence of a specific problem in unvaccinated children will determine cause and effect. Anecdotal evidence will be of no use here.

Because you are weighing one risk against another, it's important to think clearly. Don't let emotional reactions to diseases or vaccine reactions overwhelm your ability to weigh the odds. If one vaccinated child in a million has gotten a severe reaction, while one unvaccinated child in ten thousand has gotten a serious disease, you probably should vaccinate, even if the one child in a million was your own. You have to really find out the statistics, because what you hear about is often distorted by various biases. For example, many people think that driving is safer than flying, whereas it's quite the other way around. Presumably the reason for the misconception is that plane crashes often kill many people at once and so they are more newsworthy than the steady and much larger loss of life in automobiles.

Specific diseases

Here are some notes on some specific diseases against which vaccinations are available.


Polio in the United States fits the standard scenario quite well. The disease has been eradicated worldwide except for a few isolated areas. The chance that your unvaccinated child will get polio is very small, and one might argue that the disease is so well contained that even if no one in the States vaccinated it would still be OK. Because of this situation, standard practice in the U.S. is no longer to give the oral polio vaccine (OPV), which had a nontrivial incidence of serious side effects. Instead there is an inactivated vaccine (IPV) which as far as we know is free of side effects.

Hepatitis B

Hepatitis B is primarily transmitted sexually or from mother to child at birth, although there is apparently some risk of transmission in other sorts of close contact. If the mother is infected with Hepatitis B than the child should be vaccinated immediately after birth and also get immune globulin (antibodies). If the mother is not infected, it would seem unnecessary to vaccinate the child before the teenage years. Unfortunately, it is unusual to test the mother, and instead children are routinely vaccinated at birth and in infancy.


The situation with tetanus is utterly unlike the standard scenario. Tetanus isn't spread from person to person, so it makes no difference if other people vaccinate. Instead one gets it from bacteria that live in the ground. Since humans are not the primary host, the disease will never be eradicated. If you don't vaccinate your child against tetanus you risk a serious disease.


Pertussis (whooping cough) is a serious disease that is controlled by vaccinations but is nowhere near being eradicated. In fact, whenever people stop vaccinating against pertussis it comes back. Even if you are willing to be a free rider, your child still has a significant chance of being exposed.


The idea of not vaccinating against chickenpox (varicella) is completely different. Here people think that the disease is mild in children and they will deliberately expose their child, essentially using the disease itself as the vaccine. It is certainly correct that having had chickenpox is completely protective against getting a new case, whereas the long-term efficacy of the vaccine is not known. Even in the short term, it is not completely effective. But there are two problems with deliberately exposing your child to chickenpox. One is that is not always such a mild disease. In fact about 1 child in 100,000 who gets chickenpox will die of it. Of course that is a small number, but it is still much higher than the number of people dying from the vaccine, which is no more than 1 in 700,000. The other problem is that having had chickenpox puts you at risk for getting shingles later in life. Shingles is very unpleasant, and the chance of getting it from the chickenpox vaccine is much lower than if one has had the disease.

Specific vaccine risks

A lot of misinformation is being passed around about vaccine risks. Part of the problem is that people whose children become sick or die shortly after being vaccinated to tend to blame the vaccinations, even if there is no causal connection. Here are some specific issues that one often hears about.


Thimerosal is a mercury based preservative used in some vaccines. Some concern has arisen over harmful side effects due to mercury in injections, and as a result this preservative has been mostly eliminated. The only childhood vaccines that still contained thimerosal in 2003 are for influenza and tetanus/diphtheria, but not the much more commonly given tetanus/diphtheria/pertussis vaccine. Thus if you're concerned about mercury, the only vaccination to avoid is influenza.

"Fetal tissue"

One sometimes hears that vaccines contain "tissue from aborted fetuses", which is not true. No tissue that came from any fetus is in the vaccine. What is true is that some cell cultures were established decades ago using cells from aborted fetuses, and that viruses for vaccinations are grown in those cell cultures. But no cell that came from a fetus is part of the vaccine, and no abortions are performed as part of the process of vaccine production.

Autism and SIDS

Some concerns have been raised that vaccinations lead to SIDS or to autism. Several carefully done studies, however, have found no such link in either case.

What we did

We have vaccinated our twins according to pretty much the standard American recommendations. We didn't find out about the Hepatitis B situation in time for the mother to be tested, so we had the newborn vaccination, and then thought it was better to continue with the regular schedule. We would not have given our children the oral polio vaccine, but that was no longer recommended by the time that they were born.

Some closing words

If you don't want to decide for yourself about vaccinations, just do what your doctor recommends. If you do want to decide for yourself, then actually think about it for yourself. Inform yourself about the diseases and the vaccines and make a reasoned decision. Don't just go along with what you heard somewhere or what someone else is doing.

A few links

Here are a few links from the Centers for Disease Control: