COVID-19 Booster Shot Wanes; Will A Fourth Dose Be Recommended?

A COVID-19 booster shot wanes fairly quickly for most recipients, although it continues to provide fairly good protection against severe novel coronavirus infection, according to a new study. Protection against contracting the Omicron variant dropped more precipitously, however, leading to questions about the need for an additional dose. Here are more details.

ATLANTA – A new report from the national Centers for Disease Control and Prevention had both good and bad news about booster COVID-19 vaccines.

The article in the Morbidity & Mortality Weekly Report advises that vaccine effectiveness (VE) against COVID-19–associated emergency department/urgent care (ED/UC) visits and hospitalizations were higher after the third dose than after the second dose. It cautions, however, that the level of protection waned with time since vaccination.

“During the Omicron-predominant period, VE against COVID-19–associated ED/UC visits and hospitalizations was 87% and 91%, respectively, during the 2 months after a third dose and decreased to 66% and 78% by the fourth month after a third dose,” according to CDC researchers. “Protection against hospitalizations exceeded that against ED/UC visits.”

The study was conducted because, while public health officials knew that protection waned after 2 doses of mRNA COVID-19 vaccines, the durability of protection after 3 doses wasn’t clear.

“In a multistate analysis of 241,204 ED/UC encounters and 93,408 hospitalizations among adults with COVID-19–like illness during August 26, 2021–January 22, 2022, estimates of VE against laboratory-confirmed COVID-19 were lower during the Omicron-predominant than during the Delta-predominant period, after accounting for both number of vaccine doses received and time since vaccination,’ the study team explains. “During both periods, VE after receipt of a third dose was always higher than VE following a second dose; however, VE waned with increasing time since vaccination.”

The authors emphasize that, during the Omicron-predominant period, mRNA vaccination was highly effective against both COVID-19–associated ED/UC encounters at 87% and COVID-19 hospitalizations at 91% within 2 months after a third dose. Effectiveness waned, however, declining to 66% for prevention of COVID-19–associated ED/UC encounters by the fourth month after receipt of a third dose and to 78% for hospitalizations by the fourth month after receipt of a third dose.

So what does that mean for the possible recommendation of a 4th dose in the United States, especially since preliminary data from Israel, where an additional dose beyond the booster is being provided to adults 60 and older.

The Israeli Health Ministery said preliminary data suggests that the fourth vaccine dose for those older adults offers threefold protection against serious illness and twofold protection against infection in the current wave driven by the Omicron variant.

The figures are based on 400,000 Israelis who received the fourth vaccine and had received three doses at least four months ago.

At a recent White House briefing on COVID-19 response, Anthony Fauci, MD, director of the National Institute of Allergy and Infectious Diseases, predicted the possibility of a “need for yet again another boost — in this case, a fourth-dose boost for an individual receiving the mRNA — that could be based on age, as well as underlying conditions.”

“So, I don’t think you’re going to be hearing, if you do, any kind of recommendations that would be across the board for everyone,” Fauci added. “It very likely will take into account what subset of people have a diminished, or not, protection against the important parameters such as hospitalization.”

Fourth doses already are CDC recommended for certain immunocompromised adults and children in the United States.

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