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.VE against symptomatic infection was significantly higher after the second dose of the CoronaVac, AstraZeneca, and Pfizer vaccines than after the first dose (primary vaccination with J&J is one dose)."Understanding the duration and effectiveness of immunity for those vaccinated with a previous COVID-19 diagnosis becomes increasingly important as the pandemic progresses and surges in new cases may occur as a result of more transmissible variants," study coauthor Julio Croda, MD, PhD, of the Secretary of Health Surveillance in Brazil, said in a Lancet press release."There has been ongoing public debate about whether previously infected individuals need to be vaccinated," he said. "Our results suggest that vaccine benefits far outweigh any potential risk and support the case for vaccination."87% lower risk of