Health officials in California and New York reported on Wednesday that people who were previously infected with COVID-19 were better protected against the delta variant than those who were vaccinated alone, suggesting natural immunity against that variant. Had a more powerful shield than vaccines.
The study found that protection against Delta was highest among people who had been vaccinated and had survived a previous COVID infection, and lowest among those who were never infected or vaccinated. went.
Nevertheless, vaccination remains the safest strategy against COVID-19, according to the report published in the US Centers for Disease Control and Prevention (CDC) Morbidity and Mortality Weekly Report.
The results do not apply to the Omicron version of the virus, which now accounts for 99.5 percent of COVID-19 cases in the United States.
“The evidence in this report does not change our vaccination recommendations,” Dr. Ben Silk of the CDC and one of the study’s authors said at a media briefing.
“We know that vaccination is still the safest way to protect yourself from COVID-19,” he said.
For the study, health officials in California and New York collected data from May to November, which includes the period when the delta variant was dominant.
This showed that people who had survived a previous infection had lower rates of COVID-19 than those who were vaccinated alone.
Silk told the briefing that this represents a change from the period when the alpha version was dominant.
“Prior to the delta version, COVID-19 vaccination resulted in better protection against subsequent infection than survival from a previous infection,” he said.
In the summer and fall of 2021, however, when Delta became the major circulating iteration of the virus in the United States, “avoidance of past infection now provided greater protection against subsequent infection than vaccination,” he said.
But gaining immunity through natural infection carries significant risks. According to the study, as of November 30, 2021, approximately 130,781 residents of California and New York had died of COVID-19.
The analysis did not include information on the severity of the initial infection, nor does it account for the full range of disease caused by prior infection.
An important limitation to the study was that it was finished before the administration of vaccine booster doses became widespread.
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 that they provide additional protection for people with prior infection. provide.
“Outside of this study, recent data on the highly infectious Omicron variant suggests that receiving a booster confers significant additional protection against infection, hospitalization, and death,” Pan said.
Silk said CDC is studying the impact of vaccinations, boosters and pre-infections during the Omicron boom and expects to release further reports when this data becomes available.
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