In the world, the BA.2 subvariant, also known as the silent Omicron, is already predominant, according to a report by the World Health Organization (WHO). Faced with the risks of an increase in cases caused by the most transmissible strain of covid-19, health authorities are beginning to indicate the fourth dose of the vaccine. This can be called the second booster dose.

This Tuesday, the team from the Center for Disease Control and Prevention (CDC) reinforced the importance of people over 50 years old receiving the fourth dose of the vaccine against covid. 

An additional shot “is especially important for those 65 and older, and those 50 and older with underlying medical conditions that increase their risk for severe disease from COVID-19, as they are the most likely to benefit from receiving an additional booster dose at this time,” Dr. Rochelle Walensky, director of the U.S. Centers for Disease Control and Prevention, said in a statement Tuesday.

Why is the fourth dose of the vaccine important?

Boosters are important because there’s evidence of “some waning of protection over time against serious outcomes from COVID-19 in older and immunocompromised individuals,” said Dr. Peter Marks, director of the Food and Drug Administration’s Center for Biologics Evaluation and Research

“Based on an analysis of emerging data, a second booster dose of either the Pfizer-BioNTech or Moderna COVID-19 vaccine could help increase protection levels for these higher-risk individuals,” Marks added.

In the same line of reasoning, the epidemiologist at the University of California at Los Angeles, Dr. Robert Kim-Farley, warned of the natural decline in immunity against covid over the months. “In some studies, a fourth dose has been able to bring the antibody level back up to what it was shortly after the third dose. That would imply additional protection,” said the expert in an interview with the LA Times.

Although it is possible to measure the production of new antibodies with the booster and know that there are no safety risks, scientists still evaluate the quality of the immunogenicity rate, that is, how well current vaccines provoke an immune response. To understand the issue, an Israeli study is underway.

It is worth remembering that, until then, the fourth dose of the vaccine was only authorized for people over 12 years of age, as long as they had some degree of immunosuppression (immunosuppressed).

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