Two studies yesterday in The Lancet Infectious Diseases confirm that COVID-19 vaccination confers substantial added protection—particularly against severe illness—to those previously infected with the virus.

In the first study, researchers in Brazil used a test-negative design to evaluate the effect of the CoronaVac, AstraZeneca/Oxford, Johnson & Johnson (J&J), and Pfizer/BioNTech COVID-19 vaccines in 30,910 people reinfected with COVID-19 and 145,055 uninfected controls. The study period was Feb 24, 2020, to Nov 11, 2021, a period that included the Delta variant surge but before Omicron.

Vaccine effectiveness (VE) against symptomatic infection in COVID-19 survivors at least 14 days after vaccine series completion was 39.4% for CoronaVac, 56.0% for AstraZeneca, 44.0% for J&J, and 64.8% for Pfizer. VE against hospitalization or death was 81.3% for CoronaVac, 89.9% for AstraZeneca, 57.7% for J&J, and 89.7% for Pfizer.

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