The Centers for Disease Control and Prevention said on Thursday that during the Delta wave of Covid infections, both vaccination and having a prior infection provided protection against infection and hospitalization from the virus.
Scientists reviewed data from New York and California to determine the level of protection offered by vaccines, previous infection, and both. Between May and November 2021, people who were unvaccinated and did not have a prior Covid-19 infection remained at the highest risk of infection and hospitalization, while those who were previously infected, both with or without prior vaccination, had the greatest protection.
Viruses are constantly changing, the CDC explained on its website.
“These changes occur over time and can lead to the emergence of new variants that have new characteristics, including ones that impact the level of immunity vaccination and/or prior infection can provide. The level of protection offered by vaccination and surviving a previous infection changed during the study period. Vaccination remains the safest strategy for protecting against Covid-19,” the health agency said.
The CDC analysis was conducted before the emergence of the Omicron variant and the findings cannot be applied to the current Omicron wave, the agency said.
Also, the study ended before booster shots were widespread, thus it doesn’t reflect a benefit of additional vaccine doses. The CDC analysis did not include information on the severity of initial infection.
