Had COVID? Getting Vaccine Boosts Resilience Even More, Studies Show

FRIDAY, April 1, 2022 (HealthDay News) -- If you've had COVID-19 but not your COVID shot, you may wonder if getting a vaccine now will really help you.

It will, two new studies say.

Researchers in Brazil and Sweden confirmed that COVID-19 vaccines provided significant additional protection for people who had already been infected with SARS-CoV-2. The vaccines were especially effective in preventing severe disease.

"Further research on the need for vaccination for those with a previous COVID-19 infection is a vital step to pandemic policy intervention including guidance on single dose or two dose vaccine protection," said Dr. Julio Croda, a professor at Universidade Federal de Mato Grosso do Sul and Fundação in Brazil.

He's among the authors of a Brazilian study that looked at the effectiveness of four vaccines given to individuals who tested positive for COVID-19 at least 90 days after an earlier infection.

The CoronaVac, Oxford-AstraZeneca, Janssen (Johnson & Johnson) and Pfizer-BioNTech vaccines all provided additional protection against symptomatic reinfection, hospitalization and death, according to the report published in The Lancet Infectious Diseases.

Effectiveness against symptomatic reinfection was 65% for Pfizer-BioNTech, 56% for Oxford-AstraZeneca, 44% for Janssen and 39% for CoronaVac.

On preventing hospitalization and death, Oxford-AstraZeneca and Pfizer-BioNTech were each 90% effective, compared to 81% for CoronaVac and 58% for Janssen.

More than 22,000 people were reinfected. In all, 1,545 were hospitalized and 290 died within 28 days of a positive test, according to the report.

The study did not include cases of reinfection from the Omicron variants.

"All four of these vaccines have proven to provide significant extra protection for those with a previous COVID-19 infection, reducing hospitalization and death," Croda said in a journal news release.

"Our results suggest that vaccine benefits far outweigh any potential risk and support the case for vaccination, including the full vaccine series, among individuals with prior SARS-CoV-2 infection," he added.

A Swedish study yielded similar results. It also did not include the Omicron variants.

While people who got COVID-19 had higher death rates in the first three months after infection, those who recovered had a lower risk of reinfection for up to 20 months, the study found. Vaccination provided additional protection for at least nine months.

"As expected, there was an increased chance of hospitalization during the first three months after the initial infection, highlighting the fact that infection-driven immunity is not without risk," said co-lead author Anna Nordström of Umeå University.

Her team also found that both one- and two-dose vaccine immunity was associated with additional protection against hospitalization beyond the level afforded by infection-driven immunity alone.

Hybrid immunity with one shot lowered the reinfection risk by 58% two months after vaccination and 45% after nine months. Two shots lowered the reinfection risk by 66% in the first two months and 56% after nine months, the findings showed.

In a commentary accompanying the study, Jennifer Juno of the University of Melbourne, Australia, wrote: "These data confirm, in a large cohort, the added protective benefit of vaccination among individuals recovered from COVID-19… [and]… clearly demonstrate the benefits of two-dose vaccination for convalescent individuals, both in terms of the durability of immunity and protection from severe disease. Looking forward, the incorporation of infection history in an immune profile of an individual, while justified, brings into question how future booster regimens should be planned for."

Both studies were published March 31 in The Lancet Infectious Diseases.

More information

The United Nations has more about COVID-19.

SOURCE: The Lancet Infectious Diseases, news release, March 31, 2022