The United States Drug Agency (FDA) authorized this Tuesday a fourth dose of the anticovid vaccines of Pfizer–BioNTech o Moderna for people over 50 years of age, at a time when the authorities are warning about a possible new wave of the pandemic.
The FDA said in a statement that it based its decision on emerging evidence that an additional booster dose, given four months after the last, improved protection against severe COVID-19 and was not associated with new safety concerns.
Additionally, immunocompromised individuals who have already received four injections, with the last one at least four months ago, are now eligible for a fifth dose. These people include those who have received organ transplants.
The vaccine Pfizer it will be available to immunocompromised people over 12 years of age, while the Moderna vaccine will be available to those over 18 years of age.
“Current evidence suggests some decline in protection over time against severe outcomes of COVID-19 in older and immunocompromised people,” FDA Senior Scientist Peter Marks said in explaining the decision.
The FDA said data from Israel, where the effects of a fourth dose administered four months after the third dose in 700,000 people, they found that an additional injection was safe.
He also cited data from a study of 154 health care workers whose antibody levels, including against delta and omicron variants, rose two weeks after receiving the fourth dose.
A study published by Israeli researchers in the New England Journal of Medicine this month indicated that three doses of messenger RNA vaccines of the current generation had peaked in terms of the immune response generated.
In other words, while three doses boost immunity levels, the fourth dose restores antibody levels to where they were shortly after the third.
Experts noted that the benefits for younger, healthier people remain unclear, saying new vaccines will likely need to be developed as the virus continues to mutate seasonally.