Second booster offers short-term COVID-19 protection, study finds

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The U.S. government, as well as pharmaceutical companies that manufacture COVID-19 vaccines, have promoted booster shots as a way to ramp up protection when inoculation from the initial round of vaccines begins to decrease. A new study has found that protection from a second booster dose of Pfizer's offering begins to wane after about four weeks, though its effectiveness against severe illness lasts longer.

Drawing on records from about 1.2 million people aged 60 or older, the findings published in The New England Journal of Medicine showed that protection against infection from the virus plateaued about four weeks after the fourth shot was administered. Among those who didn't get the second booster, the infection rate was about twice as high.

By the eighth week after the shot, however, the added protection all but evaporated, with the infection rate almost identical between those patients and the ones who had foregone a second booster.

More encouraging was the second booster's lasting effectiveness against severe COVID-19. A month after getting the shot, the rate of severe disease was 3.5 times lower in that group than in those who had only received three shots. That protection still held after about six weeks.

WHAT'S THE IMPACT

The results provide evidence for the effectiveness of a second booster dose of the Pfizer/BioNTech vaccine, at least in terms of preventing severe reactions to the coronavirus. 

While protection against actual infection wanes quickly, this isn't a surprising development. It has long been known that the vaccines are better at preventing acute disease than the infection itself. A November 2021 study in the BMJ confirmed this, finding that breakthrough infections can occur even in countries and locales with high vaccination rates.

The boosters have shown the ability to provide needed protection for people who are immunocompromised, including those with cancer, who are often given immunosuppressive treatments that weaken their innate immune defenses. 

If cancer patients become infected, they are not only susceptible to developing severe COVID-19 but also risk interruptions to their cancer treatment or monitoring. Because of this, COVID-19 vaccination is recommended for all cancer patients, as is a third booster vaccination, given that immunity wanes over time, according to research published in the European Journal of Cancer.

The results could inform ground-level care at hospitals and health systems as clinical staff struggle to keep up with routine patient care during a relentless pandemic that has strained resources and stretched staff and margins.

THE LARGER TREND

The Food and Drug Administration in March authorized both Pfizer and Moderna to give a second booster dose of their COVID-19 vaccines to individuals aged 50 and older and to those who are immunocompromised. The additional shot follows the completion of a three-dose primary vaccination series at least four months after the first booster.

In addition, the FDA authorized a second booster dose of the Pfizer-BioNTech COVID-19 vaccine for individuals aged 12 and older with certain kinds of immunocompromise at least four months after the first booster. This includes people who have undergone solid organ transplantation or who are living with an equivalent level of immunocompromised conditions.

A second booster dose of the Moderna COVID-19 vaccine may be administered to individuals aged 18 and older with the same kinds of immunocompromise, also at least four months after the first booster, the FDA said.

The Pfizer vaccine was authorized previously under Emergency Use Authorization (EUA) as a single booster administered to individuals aged 12 and older who had completed the primary vaccination series, as well as to those 18 and older who completed primary vaccination with another authorized or approved vaccine. 

On January 31, the FDA approved the Biologics License Application for Moderna's COVID-19 vaccine to prevent the disease in people 18 and older. Previously, Moderna's vaccine was available under EUA in the U.S.

Twitter: @JELagasse
Email the writer: jeff.lagasse@himssmedia.com