US: FDA and CDC guidelines on boosting doses of covid-19 vaccines

Under new FDA guidelines, Pfizer and Moderna mRNA vaccines have been approved for a booster dose in all adults after completion of their vaccination with an approved COVID-19 vaccine. The Doctors of the Therapeutic Clinic of the Medical School of the National and Kapodistrian University of Athens Theodora Psaltopoulou, Panos Malandrakis, Giannis Danasis and Thanos Dimopoulos (Rector of EKPA) summarize the relevant announcements.

The approval of the booster dose is intended to provide continuous and better protection against serious disease, especially as immunity declines over time six months after vaccination of individuals with the Pfizer or Moderna vaccine, or two months after vaccination with the Johnson vaccine.

The decision for the booster dose for all was based on data from the immune response elicited by the vaccines. In the case of Moderna, the 149 participants who received the extra dose at 6 months in the approving clinical trial were compared with 1,055 who simply completed the vaccination regimen, who increased the antibody titer one month after the boost. Respectively for Pfizer the data from 200 people who received the third dose and had a better antibody response were analyzed.

Data were presented from a prospective randomized Pfizer study in which 10,000 volunteers who had received the second dose of the vaccine were randomized to receive a third dose and the other half to take an inactive placebo. Sickness (but without the need for hospitalization) was found in six of the 5,000 people who received the third dose of the vaccine compared with 123 of the 5,000 people who received the placebo (ie did not receive a third dose of the vaccine). Therefore, boosting the vaccine was 95% effective in preventing SARS-CoV-2 disease.

Regarding the cases of pericarditis / myocarditis that have been described after the administration of mRNA vaccines, more recent data indicate that these are two cases per 1 million doses of vaccine. Common side effects after the booster dose were pain, redness and swelling at the injection site, fever, headache, myalgias, arthralgias and more often than the initial doses axillary lymphadenopathy at the vaccination site.

The CDC recommends that adults over the age of 18 have the opportunity to receive the booster dose six months after the second dose, while for adults 50 years and older there is a strong recommendation that the booster dose be given.

Source: ΑΠΕ-ΜΠΕ