Two-dose COVID-19 vaccines provided significant protection against hospitalization and death in people who previously battled an infection with the novel coronavirus before they got jabbed.

A new study reported the potential of two-dose vaccines and their effectiveness in people who have recovered from a previous COVID-19 infection. The researchers found that those who survived the disease and developed natural immunity benefited from the vaccines.

Protection From Two-Dose Vaccines

The team studied more than 210,000 cases in Brazil who developed symptomatic illnesses at least 90 days after their initial bout with SARS-CoV-2. Among them, 30,910 tested positive through RT-PCR, consistent with reinfection.

Of the positive cases, 22,000 individuals got vaccinated after battling an infection. The team found that the Pfizer, Johnson & Johnson, AstraZeneca, and CoronaVac vaccines prevented 40% to 65% of severe complications. The two-dose vaccines — Pfizer, AstraZeneca, and CoronaVac — also impressed the researchers by preventing 80% to 90% of hospitalizations and deaths.

“We 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,” lead author Jason Andrews, MD, said in a press release.

“Some countries consider one vaccine dose to be fully vaccinated for people with prior infection immunity, and these findings argue against that policy,” the associate professor of infectious disease at Stanford Medicine added.

Protection Against Symptomatic Reinfections

All four vaccines offered protection against symptomatic reinfections at varying rates. The single-dose Janssen vaccine from Johnson & Johnson prevented 44% of symptomatic reinfections. The two-dose formulations of CoronaVac provided 39.4%, AstraZeneca gave 56%, and Pfizer afforded 65% protection against symptomatic illnesses.

“CoronaVac’s moderate effectiveness at preventing symptomatic infection is consistent with findings from clinical trials, but it is really effective for the things we care about—hospitalizations and deaths. This finding is really important for the many countries that are reliant on CoronaVac,” Andrews noted.

To identify which vaccine was administered and how many doses had been given to each case, the team used Brazil’s national vaccination database. This allowed them to determine how effective the vaccines were against symptomatic illness, hospitalization, or death.

The study, conducted by Andrews and his colleagues in Brazil, was published in The Lancet Infectious Diseases in late March.

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