The Why of the When: The Infant Vaccine Schedule

It always brightens my day to have parents bring their newborn into my office for check ups. I love to help parents do everything they can do to keep their child healthy. Is the car seat ok? What foods should the child eat? Is the house appropriately safety proofed? Of course, I also get questions about vaccines. Do they have to get so many and ultimately are they safe? My answer is always that the benefits of the vaccines outweigh the risks and that the parents should be proud that they are doing what they can to keep their child healthy.

I try to emphasize that the timing of the vaccines is important. Physicians and scientists don’t pick these timelines out of a hat.  They are the result of understanding how a child’s immune system works, previous testing to see how children’s immune systems respond to vaccines at various ages, and knowing when a child may get exposed to a particular bacteria or virus.

To review, antibodies are proteins created by particular white blood cells to ward off bacteria and viruses. Antibodies are, for the most part, specific for the particular bacteria or virus.  An antibody to the bacteria that causes meningitis won’t necessarily do anything to protect your child against whooping cough. (As an aside, studies have shown that giving the measles vaccine does help to prevent other deaths from other infectious diseases as well but that’s a different blog topic for another blog post!).

The immune system of a newborn is pretty fascinating. At birth, babies have a difficult time creating their own antibodies. Fortunately, mom passes on antibodies through the placenta.   While this provides the baby some protection, over the next 6-12 months, mom’s antibodies start to decline. The rates of antibody decline for particular viruses and bacteria are different.

Another interesting factor is if we give a vaccine for a particular disease to a child who still has some of mom’s antibodies for that disease, the child may not generate their own antibodies. This is particularly true with measles, which is why we wait until a year of age to give the first measles vaccine. With other infections, like hepatitis B, mom may not have antibodies to pass on to the child and children can contract hepatitis B within the first month of life.  Thus, we give a hepatitis B vaccine before the child is discharged from the hospital after being born.

Finally, for some infections like Human papillomavirus (HPV) or bacterial meningitis, exposure is highest when kids are in their teens so we try to vaccinate them before they are exposed. And for HPV, we’ve just learned that if we give it to kids 11-12, they have a better immune response than older teens so that they only need two vaccines instead of three.

As always, I encourage you to ask your doctor or provider if you have questions.  There can be some minor leeway with timing but be assured there is a lot of science behind the immunization schedule.   The goal is to make children and families as healthy as possible, as safely as possible.


We are participating in the CDC's NIIW Blog-A-Thon. Check out other contributions on the CDC Blog-A-Thon page

Andy Pasternak, MD, MS

Dr. Andy Pasternak is a family medicine practitioner who founded the Silver Sage Center for Family Medicine in Reno, NV. Silver Sage Center for Family Medicine provides high quality health care for the entire family, treating the entire spectrum of medical conditions ranging from simple ear and sinus infections to more complex problems like heart disease and cancer.