Dr. Farber’s Blog

Vaccines Part 1

This will be a three-part blog. I will look first at vaccines in general, and then subsequently COVID and RSV vaccines. I am not going to dwell on anti-vaccine sentiments; I will start with the premise, backed by countless studies, that they are valuable. Indeed, vaccines are probably the second most effective public health measure ever (good hygienic measures, such as a safe water supply, are far and away the most important).

We need to go over some basic science to start. Don’t worry, there won’t be a quiz.

When our body is invaded by germs such as bacteria and viruses, it makes antibodies, proteins which can fight off the invaders. The body is then, in most cases, able to ‘remember’ the invader, so that it can mount a future antibody response if attacked again by the same germ.
Vaccines stimulate the body to make these necessary antibodies. There are two main categories of vaccines. The first are inactive ones, usually containing only parts of the germ. As such, the body can make antibodies to these important components, and thus are capable of fighting off infection. However, since they are inactivated, the vaccines are incapable of causing infection themselves. Most vaccines fall into this category.

The other class of vaccines is live ones. The three most commonly used in pediatrics are for rotavirus, MMR (measles-mumps-German measles, German measles being the popular term for rubella), and chicken pox (varicella). These viruses have been weakened (‘attenuated’ is the technical term), so that they do not cause infection themselves unless given to a patient with a markedly abnormal immune system.

Most vaccines have to be given several times to build up a sufficient response. This is referred to as the primary series. The Prevnar and Pentacel vaccines we give at two, four and six months of age fall into this category. Immunity often wears off over time, hence the need for booster vaccines. One such vaccine, which requires boosting throughout the lifetime, is tetanus, which should be given every ten years. Other vaccines do not seem to require boosters as adults; the vaccines for hepatitis A and B fall into this category. I said ‘do not seem to’ because, while their efficacy and safety have been well established, they have not been around long enough to see if, for example, a booster will be needed after 60 years.

(Just to give a digression with a little bit of medical trivia. Although we often refer to the MMR and chicken pox vaccines given at age 4 years as boosters, this is inaccurate. The second dose of these is given because some children do not mount a response to the first vaccine, rather than being needed to boost immunity. While it is possible to do a blood test to see if a given child actually needs this second vaccine, we do not do this for several reasons. The blood test is expensive. It can be difficult to draw blood in young children, and doing so is often more painful than the vaccine itself. Lastly, it requires an extra trip, and associated time spent, to go to the lab to have this done. We are quite certain that the second vaccine is safe, even if your child is already immune, so that giving the vaccine rather than testing the blood is the more practical approach).

Now that you have a grasp of the science, next time I shall move on to discuss the COVID vaccine. In the meantime, please make sure you and your loved ones have had, or soon get, their flu vaccines this year.