COVID Boosters Might Be Less Than 20% Effective After a Few Months: Study

An Italian review of COVID studies found that boosters restore vaccine effectiveness against omicron initially, but that protection falls off quickly

COVID booster shots appear to be less than 20% effective against infection with the omicron variant of the virus just a few months after the booster is given, a new study found this week.

The Italian study, which is a pre-print review and re-analysis of prior studies and has not been peer-reviewed, suggests boosters are effective in the short term to restore protection against the virus. But over just a few months, that wanes quickly.

"Booster doses were found to restore the VE [vaccine effectiveness] to levels comparable to those acquired soon after administration of the second dose; however, a fast decline of booster VE against Omicron was observed, with less than 20% VE against infection and less than 25% VE against symptomatic disease at 9 months from the booster administration," the authors wrote in the paper released Wednesday.

It's a crucial question to understand, given that boosters widely became available about 9 months ago in the United States, and that a new surge is now happening with the BA.5 variant of omicron -- which appears to be better at reinfecting people than any past strain of the virus.

Overall, the researchers found that nine months after administration, two doses of a vaccine were less than 5% effective at stopping a symptomatic omicron infection, and three doses were no more than about 22% effective.

According to the CDC, less than a third of Americans have had a first booster dose at any point since they became available, and only about 5% of Americans have had a second booster dose.

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