January 20, 2022

CDC: Those recovered from COVID-19 less likely than vaccinated to get Delta variant

Editor's Note

The Centers for Disease Control and Prevention, on January 19, released a study showing that in New York and California, both vaccination and prior infection offered protection against COVID-19, but those who had recovered from COVID-19 were less likely than vaccinated individuals to get infected during the Delta wave.

Among the findings:

  • From May to November 2021, case and hospitalization rates were highest among those who were unvaccinated and who had not had a previous COVID-19 infection.
  • Before Delta became the predominant variant in June, case rates were higher in those who had a previous COVID-19 infection than those who were vaccinated alone.
  • By early October, after Delta became dominant, case rates were lower in those who had a previous infection than those who were vaccinated alone.
  • With the Omicron variant, evidence suggests decreased protection from both vaccine- and infection-induced immunity.

Further studies are needed to establish duration of protection from previous COVID-19 infection by variant type, severity, and symptommatology, including for the Omicron variant, the researchers say.


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