The Food and Drug Administration on Tuesday authorized a second booster dose of the Pfizer-BioNTech and Moderna Covid-19 vaccines for adults 50 and older.
People are eligible to receive the additional dose at least four months after receiving their first booster, the the FDA said in a statement.
Dr. Rochelle Walensky, director of the Centers for Disease Control and Prevention, expected to post a statement signing the additional shot shortly.
The FDA had already authorized a fourth injection for immunosuppressed people. On Tuesday, the FDA also authorized a fifth injection, or a second booster, for that group. Previously, immunocompromised people were allowed to receive a three-dose primary series of a vaccine followed by a booster.
Tuesday’s decision bypasses the independent panel of experts from both the FDA and the CDC, which issued recommendations to agencies during the pandemic on whether they should authorize additional injections and, if so, for which groups.
The proportion of people who have received their first booster remains low in the United States, with less than 50 percent of those eligible for a booster having received one, according to CDC data.
Officials may have a hard time persuading people to get a second booster as Covid cases, hospitalizations and deaths remain low, according to some people. lack of urgency and having a reduced fear of illness, experts say.
Also, many say that the US mishandled the pitch of the first booster shot last year when he confusingly authorized the dose.
The move comes as federal health officials assess whether an extremely contagious disease omicron subvariant, known as BA.2it will become a substantial threat at home as it spreads across Europe and other parts of the world.
The subvariant accounts for about 55 percent of new cases in the country, according to the latest CDC data.
Both Pfizer and Moderna asked the FDA this month to authorize a second booster, arguing that an additional booster is now needed because research shows the protection of the initial booster wanes after a few months. Pfizer’s application was limited to adults age 65 and older; Moderna’s was for all adults.
Among the studies cited is A study from the CDC, which found that the effectiveness of the Pfizer and Moderna vaccines against hospitalization fell from 91 percent two months after the initial booster dose to 78 percent after four months. The study included the months of December and January, when the omicron variant was rapidly spreading across the US.
experts They are divided on whether an additional dose is needed at this time, noting that while the protection against infection is relatively low, two doses and a booster still provide great protection against serious illness, hospitalization, and death, especially in young, healthy people.
However, many experts noted that a second booster may be needed for certain groups, such as older adults or people with underlying medical conditions, in the future.
Other countries, including Chile, Israel and Sweden, already allow a fourth dose of vaccine for certain vulnerable populations.
John Moore, a professor of microbiology and immunology at Weill Cornell Medical College, said the FDA’s decision to allow a second booster for people up to age 50 “seems overly cautious” because there isn’t a lot of data showing that people under 65 years of age would benefit from the additional shot.
He also questioned the timing, noting that Covid cases and hospitalizations remain at low levels and there is no sign yet of an increase in cases during the summer months.
“So what if there is a sudden increase in winter?” Moore asked. “Would people then be expected to get dose 5 in the fall? Is the repetitive boost now going to be national policy?”
Dr. Paul Offit, a vaccine expert at Children’s Hospital of Philadelphia and a member of the FDA’s advisory committee, also questioned the agency’s reasoning for including the younger age group.
He also said he is concerned about the possibility of “immune depletion” frequent reinforcements. This is when the immune system does not mount the same type of antibody response as it did with the previous injections.
The second boosters use the same formulation and dosage as the initial adult boosters: 30 micrograms for Pfizer and 50 micrograms for Moderna.
Both companies said the extra boosters were generally well tolerated by people in the trials.