Study Shows Natural Immunity More Protective Than Vaccination During Delta Surge

(Reuters/Hamodia) —
A man administers himself a COVID-19 test North Las Vegas, Nevada. (AP Photo/John Locher)

People who had previously been infected with COVID-19 were better protected against the Delta variant than those who were vaccinated, suggesting that natural immunity was a more potent shield than vaccines against that variant, California and New York health officials reported on Wednesday.

Protection against Delta was highest, however, among people who were both vaccinated and had survived a previous COVID infection, and lowest among those who had neither been infected nor vaccinated, according to the study, published in the CDC’s Morbidity and Mortality Weekly Report.

For the study, health officials in California and New York gathered data from May through November, which included the period when the Delta variant was dominant.

It showed that people who survived a previous infection had lower rates of COVID-19 than people who were vaccinated alone.

That represented a change from the period prior to Delta, when vaccination resulted in better protection against a subsequent infection than did surviving a previous infection.

Likewise, a portion of the study measuring hospitalizations — which was conducted only in California but not New York — showed that vaccination provided stronger protection than natural immunity prior to the Delta period, but that during Delta, natural immunity gave better protection against hospitalization than did the vaccine.

But acquiring immunity through natural infection carries significant risks. According to the study, by November 30, 2021, roughly 130,781 residents of California and New York had died from COVID-19.

“The evidence in this report does not change our vaccination recommendations,” Dr. Ben Silk of the CDC and one of the study’s authors told a media briefing. “We know that vaccination is still the safest way to protect yourself against COVID-19.”

The analysis did not include information on the severity of initial infection, nor does it account for the full range of illness caused by prior infection.

One important limitation to the study was that it ended before administration of vaccine booster doses was widespread. Also, results do not apply to the Omicron variant of the virus, which now accounts for 99.5% of COVID-19 cases in the United States.

Dr. Erica Pan, state epidemiologist for the California Department of Public Health, said in an email that the study “clearly shows” that vaccines provide the safest protection against COVID-19 and they offer added protection for those with prior infections.

“Outside of this study, recent data on the highly contagious Omicron variant shows that getting a booster provides significant additional protection against infection, hospitalization and death,” Pan said.

Silk said the CDC is studying the impact of vaccination, boosters and prior infection during the Omicron surge and expects to issue further reports when that data becomes available.

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