On November 19, 2021, the FDA announced that it amended the emergency use authorizations (EUA) for both the Moderna and Pfizer-BioNTech COVID-19 vaccines authorizing use of a single booster dose for all individuals aged 18 years and older after completion of primary vaccination with any FDA-authorized or approved COVID-19 vaccine.

The EUA for a single booster dose for individuals aged 18 years and older for the Moderna (administered as half of the dose of a primary series dose) and Pfizer-BioNTech COVID-19 vaccines is based on the FDA's analysis of immune response data that supported use in the previously authorized populations for boosters.

With regard to the Moderna COVID-19 Vaccine booster dose, the FDA examined the immune response data from 149 participants who were age 18 years and older from the original clinical studies who received a booster dose at least 6 months after their second dose and compared it to the immune responses of 1,055 study participants after completing their two-dose series. The antibody response against the SARS-CoV-2 virus 29 days after a booster dose of the vaccine demonstrated a booster response.

For the Pfizer-BioNTech COVID-19 Vaccine booster dose, the FDA examined the immune response data from approximately 200 participants aged 18 through 55 years who received a single booster dose about 6 months after their second dose. The antibody response against the SARS-CoV-2 virus 1 month after a booster dose of the vaccine, when compared with the response 1 month after the two-dose primary series in the same individuals, demonstrated a booster response.

Since Moderna and Pfizer-BioNTech initially submitted safety and effectiveness data on a single booster dose following primary vaccination to the FDA, additional real-world data have become available on the recently increasing number of cases of COVID-19 in the United States and on the risk of myocarditis and pericarditis following vaccination with these vaccines. These additional data allowed the FDA to reexamine the benefits and risks of the use of these vaccines in the general adult population.

The FDA has determined that the benefits of a single booster dose of either the Moderna or Pfizer-BioNTech COVID-19 vaccines outweigh the risks of myocarditis and pericarditis in individuals aged 18 years and older when used following completion of primary vaccination to provide continued protection against COVID-19 and the associated serious consequences that can occur, including hospitalization and death.

Both of the manufacturers of the mRNA vaccines are conducting postauthorization/postmarketing studies to evaluate known serious risks of myocarditis and pericarditis. In addition, the FDA and the CDC have several systems in place to continually monitor COVID-19 vaccine safety and allow for the swift detection and investigation of potential safety concerns.

The FDA noted that the fact sheets for both vaccines for recipients and caregivers and for healthcare providers contain information about the potential adverse effects (ADRs), including the risk of myocarditis and pericarditis and the most commonly reported ADRs by individuals who received a booster dose of the vaccines were pain, redness and swelling at the injection site, as well as fatigue, headache, muscle or joint pain, and chills. They also indicated that swollen lymph nodes in the underarm were observed more frequently following the booster dose than after the primary two-dose series.

In the press release, Acting FDA Commissioner Janet Woodcock, MD, stated, "Throughout the course of the COVID-19 pandemic, the FDA has worked to make timely public health decisions as the pandemic evolves. COVID-19 vaccines have proven to be the best and highly effective defense against COVID-19. Authorizing the use of a single booster dose of either the Moderna or Pfizer-BioNTech COVID-19 vaccine for individuals 18 years of age and older helps to provide continued protection against COVID-19, including the serious consequences that can occur, such as hospitalization and death."

The content contained in this article is for informational purposes only. The content is not intended to be a substitute for professional advice. Reliance on any information provided in this article is solely at your own risk.


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