Vaccines for Children Under 5: Experts Answer Parents’ Questions

Finally, virtually every American will be eligible for a COVID-19 vaccine, with protective shots available for children younger than 5—a year and a half after the oldest Americans started getting immunized.

The U.S. Food and Drug Administration (FDA) has authorized the Moderna and Pfizer COVID-19 vaccines for children ages 6 months to 5 years; previously, only children 5 and older were eligible for a vaccine. This will give nearly 18 million children added protection against the virus, which has disrupted daily life for much of their young lives.

The Moderna vaccine will be given in two doses, one month apart. The Pfizer vaccine will be given in a three-dose series, with the first two doses given three weeks apart and the third dose given two months after the second dose.

We asked UNC Health pediatric infectious diseases specialists Thomas H. Belhorn, MD, PhD, and Zach Willis, MD, MPH, to answer some common questions parents may have.

Are the COVID-19 vaccines safe and effective for children under 5?

Yes. The FDA found the Moderna and Pfizer vaccines to be effective and safe in children under age 5. Both vaccines protected children from infection, but more importantly, from severe illness and death even if children were infected.

In clinical trials, the Moderna vaccine was 50 percent effective at preventing a COVID-19 infection in children younger than age 2 and 37 percent effective in children ages 2 to 5 years.

“Data on a Moderna booster is still being evaluated, but it is likely that a booster dose of the Moderna vaccine will be recommended,” Dr. Belhorn says.

The Pfizer vaccine was 76 percent effective at preventing a COVID-19 infection in children younger than age 2 and 82 percent effective in children ages 2 to 4 years.

“Studies in children 6 months of age and older have shown the vaccines significantly reduce the chance of a COVID-19 infection,” Dr. Willis says. “In addition, we expect the vaccines for younger children will provide protection from the most severe outcomes of COVID-19, such as hospitalization and death.”

Why did it take so long to make this vaccine available to the youngest children?

Vaccine studies were first conducted in adults. Once they were found to be safe and effective in adults, clinical trials included adolescents and then young children, moving down to 6 months of age. Vaccine manufacturers wanted to make sure the vaccines were both safe and effective in adults before progressing to the youngest children in the same studies.

“There are good reasons why the youngest children are the final group in a vaccine rollout. All clinical trials on humans prioritize safety, but growing children are a special population,” Dr. Belhorn says. “Researchers wanted to make sure they had as much information as possible on safety, efficacy, dosage and immune response before giving the vaccines to children.”

Pfizer initially tested a two-dose regimen that was proven safe but did not produce a strong enough antibody response, necessitating testing a third dose and delaying approval.

How were the vaccines tested in this age group?

Children were given the vaccines, and then researchers collected data that included safety studies by monitoring these children for any side effects or new signs of symptoms. Researchers then ran blood tests to see if the vaccine created a strong immune response.

To find out how effective the vaccines were in children who received the actual vaccine compared to children who received the placebo, children in both groups were followed to see if they got a COVID-19 infection.

“The children who received either vaccine were much less likely to get a COVID-19 infection than the children who received the placebo,” Dr. Willis says.

How do parents choose between the vaccines?

Vaccine studies to date have shown that the two vaccines are very similar in safety and effectiveness.

“There is no preference of one of these two vaccines, and both are recommended for use,” Dr. Belhorn says. “You may choose a vaccine based either on personal preference or which vaccine is available.”

What types of side effects should parents expect?

Side effects are minor and similar to other vaccines. The clinical trial data for this age group showed no serious side effects.

Side effects may include irritability and crying in the youngest children (under age 3) and feeling tired in the older age group (over age 3). In clinical trials, 8 to 20 percent of children had a short-term fever following vaccination.

“There is no need to premedicate before your child gets the vaccine, but it is fine to give acetaminophen (Tylenol) or ibuprofen (Advil) after vaccination for aches or fever,” Dr. Willis says.

If very young children have low rates of serious illness, why bother vaccinating them?

While it is true that young children are less likely to have serious illness with COVID-19, data from the Centers for Disease Control and Prevention (CDC) show that COVID-19 is the fifth leading cause of death in children ages 1 to 4, Dr. Belhorn says. Doctors are also still learning about long COVID, in which COVID symptoms last for weeks or months, which can also affect children.

Children with COVID-19 can infect older individuals who are more likely to get a serious illness. Infected children and their peers continue to experience school and day care closures and quarantines because of the virus.

If my child had COVID-19 recently, should they be vaccinated?

Yes, and they can receive the COVID-19 vaccine after they have recovered from the illness.

“Children who have had COVID-19 previously can still have re-infection with a new variant, and vaccines and boosters can help prevent that,” Dr. Belhorn says. “The vaccines provide better immunity than natural infections in many settings.”

How long will it take for a vaccinated child to be protected?

Children have high antibody levels within two weeks of finishing the vaccine series, Dr. Wilis says.

The Pfizer vaccine needs three doses for maximum effectiveness, and studies show it is not as effective unless a child receives all three doses. The Moderna vaccine is effective after the initial two-shot series. There is not yet a booster shot from either manufacturer for children younger than 5.

Once my child is vaccinated, can we relax precautions?

You can feel safer after your child is vaccinated, but additional precautions such as masking indoors and avoiding crowded areas are still recommended in some settings, especially in areas where the COVID-19 infection rates are high.

“We would recommend vaccinating young kids as soon as possible,” Dr. Belhorn says. “At this time, we are still seeing large numbers of COVID-19 infections in all age groups. As we’ve seen in adults, even though protection against infection did decrease over time, breakthrough infections are still much less likely to be severe in vaccinated people than those who are unvaccinated.”


Visit unchealthcare.org/vaccine for the latest information on the COVID-19 vaccines and boosters.