Vaccines provide additional protection for those immunized against a previous COVID-19 infection


In one study, researchers sought to determine whether the four COVID-19 vaccines licensed for use in Brazil – CoronaVac, Oxford-AstraZeneca (ChAdOx1), Janssen (Ad26.COV2.S) and Pfizer-BioNTech (BNT162b2) – offered additional protection against symptomatic infection, hospitalization and death, to people reinfected with SARS-CoV-2.

Vaccinations against COVID-19 are highly effective in preventing symptomatic infection and hospitalization in people who have never been infected, but their effectiveness in infected people remains unclear. Knowing how long people are immune after a COVID-19 vaccination is critical as the pandemic continues and new transmissible variants emerge.

Vaccine efficacy against symptomatic reinfection was 39% for CoronaVac, 56% for Oxford-AstraZeneca, 44% for Janssen and 66% for Pfizer-BioNTech. It was 90% for Oxford-AstraZeneca, 80% for Janssen and 80% for Pfizer-BioNTech. In the first 28 days after a positive test, 1,545 people were hospitalized and 290 died.

The extent of protection after COVID-19 infection varies among people. These four vaccines have been shown to provide additional protection to people who have already been infected with COVID-19, reducing hospitalizations and deaths.


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