UF Health expert Q&A on booster shots for kids

As cases of the omicron variant continue to surge, two federal agencies have approved booster shots of the Pfizer-BioNTech COVID-19 vaccine for 12- to 15-year-old children. 

Dr. Sonja A. Rasmussen, a professor in the departments of pediatrics and epidemiology at the UF College of Medicine and the UF College of Public Health and Health Professions, discusses what parents should know about the Pfizer booster shot.

Question: What is a booster shot and why is it needed?

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Answer: A booster is an extra dose of vaccine that helps immunity last longer. Booster shots are common for many vaccines. Many of the vaccines children already receive require booster doses, including the measles-mumps-rubella, or MMR, and hepatitis B shots. Adults also need boosters, such as an added dose of the tetanus shot every 10 years. The COVID-19 vaccines initially provided a very high level of immune protection. However, we have learned that our level of immunity declines over time. For most people, the vaccines still provide good protection against serious disease, hospitalization and death. But the waning immunity means more people who were vaccinated can get infected and mildly sick with COVID-19. In addition, the omicron variant that is causing most of the COVID-19 cases in the United States right now is highly contagious. To protect against the omicron variant, we need an even higher level of immunity. By getting a booster dose, we get that additional protection.

Q: Is this the same dose as the original Pfizer/BioNTech vaccine and how soon does booster shot immunity establish itself?

A: The booster dose is the same as each of the original two doses of the Pfizer vaccine. That dose has been shown to be safe and effective. It takes about one to two weeks for the booster shot to be effective. 

Q: How much is known about the booster shot’s ability to protect against the omicron and delta variants?

A: The good news is that the booster shot gives us the additional protection that we need to tackle those variants. It provides strong protection against severe disease, hospitalization and death from the omicron and delta variants. However, no vaccine is 100 percent effective. At this time, when there are so many people with COVID-19, we need multiple layers of protection. Until the numbers of cases come down, we need to continue to wear masks and avoid crowded places with poor ventilation.

Q: The Centers for Disease Control and Prevention recommended the Pfizer vaccine for children ages 12 to 15 in May. What data and important insights about the vaccine in that age group has the scientific community gotten since then?

A: At the end of 2021, over 18 million doses of Pfizer vaccine have been given to children and teens ages 12 to 15. The vaccine has been shown to be safe and effective in this age group. Side effects in this age group are similar to those seen in adults. They are typically mild and last one to three days.

Q: The FDA also significantly shortened the booster shot waiting period to at least five months for everyone over age 12. What were the data and factors driving that decision?

A: The time between the second dose of the Pfizer vaccine and the booster has been shortened from six months to five months. That is because studies show that by five months, protective antibodies had dropped to a level where additional protection was needed. Of note, the time recommended between the initial series and the booster doses differ, depending on the type of vaccine received. People (children or adults) who received the Pfizer vaccine should get the booster at least five months after their second dose. For adults who received the Moderna vaccine, the booster should be given at least five months after their second dose. For adults who received the Johnson & Johnson single dose vaccine, the booster should be given at least two months after their first shot.

Q: What has the scientific community learned about the prevalence of myocarditis among vaccine recipients after it was put into widespread use?

A: Myocarditis is an inflammation of the heart muscle that is a very rare condition caused by the mRNA (Pfizer and Moderna) COVID-19 vaccines. Myocarditis occurs more often in male adolescents and young adults and is more often seen after the second dose of the vaccine. When it is seen, it occurs within a week after vaccination. Most patients who develop myocarditis after receiving the vaccine respond well to medications and rest, and feel better quickly. 

We now have information on millions of teens who have received the Pfizer vaccine. In the group with the highest risk (males 18-26 years), the chance of getting myocarditis is about 1 in 10,000 to 20,000. The chance of getting myocarditis from a COVID-19 infection is higher than the chance of getting it from the vaccine. 

Also, studies from Israel have shown that the chance of getting myocarditis after a booster dose is similar after the second dose of vaccine. In a study of 44,000 children age 12 to 15 years old in Israel who received a booster shot, two developed mild myocarditis.

Q: Will we need to continue to have boosters?

A: We don’t know the answer to that question right now. That depends on two things: our immune systems and the virus. We will need to continue to study the immune response after booster shots to see if the protection wanes again. And we need to keep an eye on the virus: If it changes enough that our immune system has a hard time recognizing it, we might need to have additional shots. It is possible that shots might be needed every year, similar to the flu shots that are recommended annually.

Q: How soon will the booster vaccine be available and where can I get one?

A: The booster is available now at sites where the COVID-19 vaccine is offered. That includes UF Health sites, doctor’s offices, local pharmacies and the Florida Department of Health in Alachua County. If you need help finding a COVID-19 vaccine or booster, go to www.vaccines.gov or call 1-800-232-0233.

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