Vaccinated persons who also had prior infection were most protected from Delta

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Thu, 2022-01-20 11:31 — mike kraft

Vaccinated With Prior Infection Most Protected During Delta Wave Data showed prior infection alone similarly protective, though CDC notes caveats Molly Walker medpagetoday

Following the emergence of the Delta variant, individuals who had a prior COVID-19 infection with or without vaccination had lower case rates than those who were vaccinated alone, data from California and New York found.

"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," reported Tomàs León, PhD, of the California Department of Public Health, and colleagues, writing in an early edition of the Morbidity and Mortality Weekly Report.

Prior to the Delta variant becoming prevalent, the highest incidence of COVID-19 was in unvaccinated individuals without a prior COVID infection, and vaccination demonstrated the most protection against a new infection. In California and New York, respectively, rates among the vaccinated and those with a prior infection were:

Vaccinated alone: 19.9-fold and 18.4-fold lower
Vaccinated with prior infection: 9.6-fold and 8.5-fold lower
Unvaccinated with prior infection: 7.2-fold and 9.9-fold lower

By early October 2021, however, that balance shifted. Compared to unvaccinated individuals without a prior COVID infection in California and New York, rates of COVID infection were:

Vaccinated alone: 6.2-fold and 4.7-fold lower
Vaccinated with prior infection: 32.5-fold and 19.8-fold lower
Unvaccinated with prior infection: 29.0-fold and 14.7-fold lower

CDC released a statement on the findings, noting important caveats -- namely that the analysis was conducted prior to the spread of Omicron and before widespread implementation of booster doses, and also that the data set did not include information on severity of initial infection among those who were previously infected. ...

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