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.
After delta became the main strain, vaccines alone grew weaker against the virus and natural immunity got much stronger.
“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.”
During a time when the delta variant was the dominant strain on Oct. 3, it changed. Case rates in vaccinated people without a previous COVID-19 diagnosis were only 6.2 times lower than unvaxxed, uninfected people — three times less effective than pre-delta. They grew to 29 times lower among unvaccinated people with a previous diagnosis, and 32.5-fold among vaccinated people with a previous diagnosis of COVID-19.
Similar figures came from New York.