Natural immunity from prior infection granted stronger levels of protection against the Delta variant of COVID-19 than vaccination alone, the Centers for Disease Control and Prevention (CDC) said in a study released Wednesday.
Before Delta became dominant, individuals who had natural immunity were experiencing higher case rates than individuals who were only vaccinated, the study found, but after Delta took hold, those with natural immunity caught COVID-19 less frequently than those who were only vaccinated.
— Adriel Bettelheim (@abettel) January 19, 2022
The study examined four categories of people — unvaccinated and vaccinated who survived a previous COVID-19 infection, and unvaccinated and vaccinated who had never been infected — in California and New York between May and November 2021. The highest case rates were among those who had neither been vaccinated or previously infected. The most protection against infection and hospitalization was in those who had both been vaccinated and survived an earlier bout with the virus.
The agency cautioned that the data in question only measured results against the Delta variant and that Omicron may present new challenges that alter the calculus of natural immunity versus vaccination.
Biden administration officials and some public health experts have repeatedly downplayed the effectiveness of natural immunity against COVID-19, but this study is only the latest to indicate that recovery from prior infection can at least rival, if not surpass, that offered from vaccination alone. Most research has shown that for maximum protection against reinfection or severe illness, those who were previously infected should still get vaccinated.
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