COVID-19 vaccines for children and adolescents: What do we do and do not know? Harvard Health Blog


Vaccines have been announced as a key measure to slow the COVID-19 pandemic and one day end it. Every day, millions of American adults receive one of the authorized vaccines that has been shown to be very effective in preventing serious illnesses that could otherwise lead to hospitalizations and deaths. In the US, most people over the age of 65 they are now completely vaccinated, protecting the most vulnerable of our population.

As an infectious disease specialist, my answers to the following questions are based on what we know so far about infection and vaccines in children and adolescents. We will need to continue to fill in the gaps as we investigate and our understanding evolves.

What do we know about how COVID-19 affects children and adolescents?

Most COVID-19 infections in children are mild or show no obvious symptoms. However, a small percentage of children are infected

  • develop a severe inflammatory condition called MIS-C in the two to six weeks following COVID-19 infection. This can happen even in children with mild or asymptomatic symptoms.
  • he gets very ill and needs hospitalization or intensive care.

More than 400 children have died from COVID-19 infection. This is higher than the number of child deaths during the deadliest flu season in the last two decades.

Vaccination of children to prevent these results is one of the most important reasons driving vaccine studies in children. In addition, vaccination of children will be essential to achieve a level of immunity in the entire population, the immunity of the herd, enough to curb the emergence of dangerous variants and end the pandemic.

What do we know so far about COVID-19 vaccines in adolescents?

  • The Pfizer / BioNTech vaccine is authorized for use in people over 16 years of age.
  • Moderna and Johnson & Johnson vaccines are authorized for use in people over 18 years of age.
  • These authorizations were based on data from participants of these ages in placebo-controlled randomized trials demonstrating the safety and efficacy of these vaccines. Efficacy measures the functioning of a vaccine under the controlled circumstances of a study. Efficacy is the smooth running of a vaccine outside of a study, when people in the community receive it.

As states expand eligibility for COVID-19 vaccines, adolescents 16 years of age or older can receive the appropriate vaccine through the same sources that adults have had access to so far. Available vaccine sites may vary depending on the condition and location of your medical care. See the search map at VaccineFinder, or your state health board.

Vaccine research conducted to date or ongoing includes the following:

  • Pfizer / BioNTech has completed a trial in children aged 12 to 15 years. This trial used the same dose and schedule of the vaccine used in adults: two doses administered three weeks apart. The company announced in a Press release that the vaccine was safe and well tolerated, elicited strong antibody responses, and was 100% effective in preventing mild to severe infections in this age group. The FDA is reviewing the data and will consider authorizing this vaccine for use in this age group. If all goes well, we could expect this vaccine to be available for 12- to 15-year-olds in the coming months.
  • Moderna completed the enrollment of 12- to 17-year-olds in a similar trial with the same dose and schedule as in adults: two doses administered four weeks apart. Data from this trial are expected in the coming months.
  • Johnson & Johnson has begun a trial of its vaccine for a small number of 16- to 17-year-olds. If the vaccine proves to be safe and effective in this age group, the trial will continue with 12- to 15-year-olds.

What about COVID-19 vaccine trials for younger children?

  • Pfizer / BioNTech and Moderna have started testing in children aged 6 months to 11 years.
  • These trials will begin by testing smaller doses than those administered to older children, adolescents, and adults. This allows researchers to determine which dose is well tolerated and still causes strong antibody results in younger children.
  • Once the dose is established, a larger number of children in these age ranges will enroll in placebo-controlled trials to evaluate the effectiveness of these vaccines.

All of these steps will take a while so they can be done without cutting any safety corners. The first vaccines are likely to be available for younger children in late 2021 or perhaps early 2022.

What is not yet known about COVID-19 vaccines in children and adolescents?

  • The duration of COVID-19 vaccine-induced immunity in children should be monitored over time. The results of these studies will help experts decide whether children will need COVID-19 vaccine boosters in the future.
  • Researchers should also study whether COVID-19 vaccines can be combined with other vaccines that children commonly receive. For now, the CDC recommends that no other vaccine be given within 14 days of the COVID-19 vaccine. This is true for people of any age.
  • Researchers will need to evaluate the impact of these vaccines on protecting children from infection with COVID-19 variants. But biologically, there would be no reason to expect differences in vaccine coverage of variants in adults compared to children.

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