The Italian study, which is a preprinted review and re-analysis of previous studies and has not been peer-reviewed, suggests that the boosters are effective in the short term for restoring protection against the virus. But within a few months, this rapidly diminishes. “Booster doses found to restore VE [vaccine effectiveness] at levels comparable to those obtained immediately after administration of the second dose. However, a rapid decline in booster VE versus Omicron was observed, with less than 20% VE against infection and less than 25% VE against symptomatic disease at 9 months after booster,” the authors wrote in the paper released Wednesday. It’s a critical question to understand, given that the amps became widely available about 9 months ago in the United States, and that a new surge is now happening with omicron’s BA.5 variant — which appears to be better at re-infection of humans by any other previous strain of the virus. Overall, the researchers found that nine months after administration, two doses of a vaccine were less than 5% effective in 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 received a first booster dose at any time since they became available, and only about 5% of Americans have received a second booster dose.
