CDC: Prior infection protected people better than vaccinations during delta surge

WHAT YOU NEED TO KNOW:

• A previous Covid-19 infection protected people better than vaccinations did during the delta wave, according to CDC.
• Researchers analyzed data from May to November 2021 to determine the impact of vaccination and previous Covid-19 infection.
• The CDC study did not include cases from the latest omicron surge.

People who had previously been infected with Covid-19 were better protected against the Delta variant than those who were vaccinated alone, a CDC study revealed. The study result suggested that natural immunity gave stronger protection 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. Protection was lowest among those who had never been infected or vaccinated, the study found.

Nevertheless, vaccination remains the safest strategy against COVID-19, according to the report published in U.S. Centers for Disease Control and Prevention (CDC) Morbidity and Mortality Weekly Report.

The CDC study did not include cases from the latest omicron surge.

“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. “We know that vaccination is still the safest way to protect yourself against Covid-19.”

For the study, health officials in California and New York gathered data from May through November 2021, 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 when the Alpha variant was dominant, Silk told the briefing.

“Before the Delta variant, Covid-19 vaccination resulted in better protection against a subsequent infection than surviving a previous infection,” he said.

In the summer and fall of 2021, however, when Delta became the predominant circulating iteration of the virus in the United States, “surviving a previous infection now provided greater protection against the subsequent infection than vaccination,” he said.

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.

One important limitation to the study was that it ended before the administration of vaccine booster doses was widespread.

Dr. Erica Pan, the state epidemiologist for the California Department of Public Health, said in an email that: “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.”

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.

Source: Reuters