Beyond COVID-19: Why kids need other vaccines, too

A vaccine needle and syringe, along with a vial carrying a vaccine, are surrounded by symbols of immunization and health.
People don't see serious illnesses anymore because of vaccines. (Image: AdobeStock/Illustration: David Chrisom, Boston Children's)

As you consider immunizing your child, it’s natural to have questions about the safety and effectiveness of vaccines. But the detection of polio in New York illustrates how diseases that were once thought to have been eradicated can reemerge when vaccination efforts lag.

While COVID-19 vaccines have understandably drawn attention during recent years, it’s important to remember that immunization against older infectious diseases can also protect your child from serious illness.

For answers to your questions about childhood vaccines, we spoke with Dr. Kristin Moffitt, a pediatric infectious disease specialist at Boston Children’s.

How does a vaccine work?

Vaccines work by generating an immune response to specific germs — generally, viruses and bacteria. A vaccine uses a germ against itself by taking an inactive or weakened version, or just a piece of the germ, and showing it to the immune system ahead of time so it knows how to attack it. Once a child is vaccinated, they now have immunity to prevent them from either getting infected or very sick. Your child will need to have some shots more than once because some vaccines wear off over time or because scientists adapt vaccines to become even more effective.

Why should I vaccinate my child if some diseases aren’t spreading?

Polio and measles are diseases that were largely eradicated in the U.S. for years because of high vaccination rates but have lately reemerged because of a decline in vaccinated families. In 2022, testing confirmed poliovirus in 100 samples in New York.

If you’re holding off vaccinating your child because you don’t see certain diseases anymore, consider that we don’t see those diseases anymore because of vaccines. Vaccinations protect your family. But there’s also a more altruistic reason to be immunized, and that’s to maintain a community level of immunity and prevent the spread of disease. When a child is immunized, they’re protecting everyone they know, especially those who are immunocompromised or too young to be immunized. 

Can vaccines do more harm than good?

Extensive research and verification goes into the development, production, and testing of vaccines — a process that has been in place for decades. It ensures that vaccines provide a high level of protection against diseases and that they are safe. For example, studies have found no link between autism and the MMR vaccine that protects against measles, mumps, and rubella. Any vaccine can cause side effects, such as a low-grade fever or sore arm, but that’s a sign your child’s immune system is learning how to fight that particular virus or bacteria. Side effects typically disappear in a few days.

Is my infant too young to be vaccinated?

Extensive research shows that a child’s immune system won’t be overwhelmed by vaccine antigens that stimulate immunity. Infants have immature immune systems and are more susceptible to infections than older children are. Getting them started with the first round of vaccinations in the first few months of life helps them start building immunity against diseases.

Does my child need all of those shots close together?

The timing recommendations consider when pathogens are most dangerous to infants and children and what is known about the distribution of infections across age groups. A lot of science goes into the schedule of vaccines the Centers for Disease Control and Prevention (CDC) recommends for your child, and this includes evaluating the safety of vaccines given on this schedule.

How effective are vaccines?

While some vaccines need to be administered only once or twice to prevent disease, some need to be given annually or more frequently because those diseases change. The flu shot, for one, is revised each year to protect against the most common strains of influenza that are circulating, so how well a particular vaccine works varies year by year. COVID-19 vaccines are also now being updated to include the original versions with ones that target Omicron strains.

Learn more about the Division of Infectious Diseases.


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