Scientists from Stanford Medicine found that people who have recovered from COVID-19 still benefit from vaccination.
They found clear evidence that COVID-19 vaccines are highly effective among people who have recovered from a previous infection, giving them benefits above and beyond the immunity they already have.
The research is published in Lancet Infectious Diseases and was conducted by Jason Andrews et al.
In the study, the team tested more than 22,000 people in Brazil who were reinfected with SARS-CoV-2, the virus that causes COVID-19.
They found the CoronaVac, AstraZeneca, Pfizer and Johnson & Johnson vaccines prevented 40% to 65% of symptomatic illnesses.
The two-dose vaccines—CoronaVac, AstraZeneca and Pfizer—prevented 80% to 90% of hospitalizations and deaths from reinfection.
The two-dose vaccines were highly effective against reinfection leading to hospitalization or death.
The effectiveness of the CoronaVac vaccine against reinfection leading to hospitalization or death was 81.3%. For Pfizer’s vaccine, that figure was 89.7%; for AstraZeneca’s, it was 89.9%.
Despite the strong immune response mounted by people with prior infection to the first dose of an mRNA vaccine, just one dose of the CoronaVac, AstraZeneca or Pfizer vaccine was less effective at preventing hospitalizations and death than the full series.
The first dose of CoronaVac was 35.3% effective at keeping people out of the hospital. Pfizer’s first dose was 61.8% effective, and AstraZeneca’s was 56.9%.
The findings showed all four vaccines offered some protection against symptomatic COVID-19 reinfections.
Two doses of the CoronaVac vaccine prevented 39.4% of symptomatic illnesses, and J&J’s single-dose vaccine stopped 44%.
Two doses of AstraZeneca’s vaccine protected against 56% of symptomatic illnesses, while two doses of the Pfizer vaccine stopped 65%.
More than 30% of the world’s population has not received a COVID-19 vaccine.
Because of inequities in the global distribution of vaccines, many of the countries just beginning to scale up their vaccine rollouts will be offering doses to people who have recovered from a previous infection.
This study suggests that vaccinating these people will prevent many future hospitalizations and deaths from COVID-19 reinfection.
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