The FDA approves in the US the fourth dose of the vaccine against covid-19 for people over 50 years of age

Vials of Moderna and Pfizer vaccines. Charles Krupa (AP)

The drug regulatory body in the United States has authorized this Tuesday a fourth dose of the coronavirus vaccines from the Pfizer-BioNTech or Moderna laboratories for people over 50 years of age and cases of immunosuppression.

We would be facing the second booster vaccine, which could be injected as long as four months have passed after the first support dose.

Now, the Centers for Disease Control and Prevention (CDC) have the last word to give the green light to their recommendation.

Through a statement, the US Food and Drug Administration (FDA) ensures that scientific evidence suggests that there is "some decrease in protection" of vaccines over time, so a second reinforcement "It would help increase the levels of protection of people at higher risk."

Pfizer's vaccine 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.

The decision comes at a time of great uncertainty, the cases of covid-19 have fallen to very low levels after the huge spikes experienced during the months of December and January due to the spread of the highly contagious omicron variant.

According to FDA scientist Peter Marks, "the benefits" of a second booster dose "outweigh the risks" of its application.

In making this decision, the drug agency relied on data provided by the Israeli Ministry of Health, which already administers second Pfizer booster doses to adults, and independent studies on Moderna, among other analyses.

In Israel, the effects of a fourth dose given four months after the third were studied in 700,000 people, and a further injection was shown to be safe.

The FDA 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 current-generation mRNA vaccines 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.

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