How effective is the second COVID-19 booster dose?

The Centers for Disease Control and Prevention (CDC) updated its vaccination guidelines recently to recommend people 50 years of age and older receive a second COVID-19 booster dose.

Additional Booster Doses

Boosting with another dose of the vaccine can increase that immunity again, so public health officials authorized an initial booster shot for most people last year. But as new variants of the virus continue to emerge, it’s time to consider another booster dose for the wider population. Already, that second booster is recommended for certain people at high risk of COVID-19 disease who could benefit from the enhanced protection provided by the additional shot.

The U.S. Food and Drug Administration (FDA), with the CDC’s backing, also authorized a second dose to severely immunocompromised individuals ages 12 and up. But for individuals in these categories, the decision to get a second booster is a complicated one.

A second COVID-19 booster dose

The FDA and CDC have said most adults ages 50 years and older can get a second booster shot of Pfizer or Moderna at least four months after their first booster shot. According to a recent study from Israel that looked at how some people tolerated a fourth shot of the Pfizer vaccine, while some people gained immunity against the omicron variant, the protection did not last for long.

“These findings suggest that protection against confirmed infection wanes quickly,” said the study, which was published last Tuesday in The New England Journal of Medicine. The study found that protection started to wane after four weeks, but it did provide protection against serious illness.

Effectiveness of the second dose

According to Dr. Marcus Pereira of Columbia University Medicine, those ages 50 to 60 who are otherwise healthy and do not have any underlying health conditions should consult their doctors about whether it would be reasonable to wait until the COVID infection rate increases.

It takes about a week for the booster to kick in, and protection wanes quickly, according to the Israeli study. Dr. Pereira suggests that those who are severely immunocompromised or over age 65 should not wait to get the second booster because of the increased risk of catching COVID-19 in those groups.