Natural immunity better protects against the Delta strain of COVID-19 than a vaccine, according to a study released by the Centers for Disease Control and Prevention (CDC) on Wednesday.
Researchers examined COVID-19 cases and hospitalizations from May through November 2021 in California and New York. The research team examined case and hospitalization rates among four cohorts of people: the unvaccinated and previously uninfected, the vaccinated and previously infected, the unvaccinated with a previous COVID-19 diagnosis, and the vaccinated with a previous COVID-19 diagnosis.
The study found that the natural immunity obtained through recovering from a bout of COVID-19 gave people a much greater degree of protection against the Delta strain of COVID-19 than receiving a COVID-19 vaccine. The study said:
By the week beginning October 3, compared with COVID-19 cases rates among unvaccinated persons without a previous COVID-19 diagnosis, case rates among vaccinated persons without a previous COVID-19 diagnosis were 6.2-fold (California) and 4.5-fold (New York) lower; rates were substantially lower among both groups with previous COVID-19 diagnoses, including 29.0-fold (California) and 14.7-fold lower (New York) among unvaccinated persons with a previous diagnosis, and 32.5-fold (California) and 19.8-fold lower (New York) among vaccinated persons with a previous diagnosis of COVID-19. During the same period, compared with hospitalization rates among unvaccinated persons without a previous COVID-19 diagnosis, hospitalization rates in California followed a similar pattern. These results demonstrate that vaccination protects against COVID-19 and related hospitalization, and that surviving a previous infection protects against a reinfection and related hospitalization. Importantly, infection-derived protection was higher after the Delta variant became predominant, a time when vaccine-induced immunity for many persons declined because of immune evasion and immunologic waning (2,5,6).See link above