ii. Vaccine Approval

III. COVID-19 Vaccine FAQs

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ii. Vaccine Approval


The U.S. Food and Drug Administration (FDA) is responsible for regulating vaccines and vaccine safety in the United States. They have issued specific guidelines for applications for either Emergency Use Authorization or Biologic License Application for COVID-19 vaccines.

All potential vaccines must first demonstrate safety and effectiveness in clinical studies, including tens of thousands of volunteers. Volunteers in these studies must be followed on average for at least 2 months to monitor side effects before an application can be filed with the FDA. The criteria for determining safety and effectiveness used by the FDA are made public in their guidelines for submission of a vaccine for authorization or approval. If the FDA decides that a vaccine meets its safety and effectiveness standards, it can make these vaccines available for use in the United States.

After a vaccine is approved for use, the FDA continues to gather post-licensure data to assure the vaccine’s safety. CDC and FDA encourage the public to report possible side effects (called adverse events).

In California, we have a Scientific Safety Review Workgroup, which will also look at the clinical trial data before the vaccine is approved for distribution within the state.

Visit these pages to learn more about vaccine safety and approval:


On May 10, 2021, the FDA granted Emergency Use Authorization for use of the Pfizer vaccine in adolescents down to age 12. The original Emergency Use Authorization for the Pfizer vaccine, which covered persons down to age 16, was expanded to include younger adolescents. No other COVID-19 vaccines are currently authorized for persons below age 18 in the United States.

In the clinical study supporting this authorization, 2,260 participants ages 12 through 15 years old enrolled in an ongoing randomized, placebo-controlled clinical trial in the United States. Of these, 1,131 adolescent participants received the vaccine and 1,129 received a saline placebo. More than half of the participants were followed for safety for at least two months following the second dose. The most commonly reported side effects in the adolescent participants, which typically lasted 1-3 days, were pain at the injection site, tiredness, headache, chills, muscle pain, fever and joint pain. With the exception of pain at the injection site, more adolescents reported these side effects after the second dose than after the first dose, so it is important for vaccination providers and recipients to expect that there may be some side effects after either dose, but even more so after the second dose. The side effects in adolescents were consistent with those reported in clinical trial participants 16 years of age and older.

In terms of effectiveness, the immune response of adolescents was at least as good as the immune response of the older participants. An analysis of cases of COVID-19 occurring among participants, 12 through 15 years of age, seven days after the second dose was also conducted. In this analysis, among participants without evidence of prior infection with SARS-CoV-2, no cases of COVID-19 occurred among 1,005 vaccine recipients and 16 cases of COVID-19 occurred among 978 placebo recipients; the vaccine was 100% effective in preventing COVID-19.

There is currently only limited evidence regarding whether the vaccine prevents person to person transmission of the virus, and the duration of protection from the vaccine is not yet known.

Read more: FDA Authorizes Pfizer-BioNTech COVID-19 Vaccine for Emergency Use in Adolescents