CDC: Natural immunity six times stronger during the Delta wave than vaccination

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Natural immunity was six times stronger during the delta wave than vaccination, according to a new report from the U.S. Centers for Disease Control and Prevention.

The report, published Jan. 19, analyzed COVID outcome data from New York and California, which make up about one in six of the nation’s total COVID deaths.

The study has limits — namely, it was done before the omicron wave and doesn’t factor in any information about boosters. It does, however, broadly agree with studies from other countries.

Vaccines were more effective at preventing infection or serious illness than natural immunity from prior infections before the delta variant became the dominant strain. After delta became the main strain, vaccines alone grew weaker against the virus and natural immunity got much stronger. This could be due in large part to the fact that vaccines began wearing off around the time delta spread, according to the study.

“Importantly, infection-derived protection was greater after the highly transmissible Delta variant became predominant,” reads the report, “coinciding with early declining of vaccine-induced immunity in many persons.”

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