Hybrid COVID-19 immunity confers high protection only in previous infections

February 01, 2023

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Bobrovitz Reports receiving grants unrelated to this study from the Canadian COVID-19 Immunity Task Force, the Robert Koch Institute, and the Public Health Agency of Canada. Boaventura is employed by Fiocruz, a federal public entity that manufactures the ChAdOx1 (Oxford-AstraZeneca) vaccine in Brazil through a full technology transfer agreement with AstraZeneca. Please see all other authors’ studies for relevant financial disclosures.

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People who were vaccinated and previously infected with COVID-19 were 97% less likely to develop a severe COVID-19 infection 1 year after their last vaccination or infection, the researchers determined.

“The landscape of population immunity has become more complex over time. There are good estimates about the level of protection provided by the COVID-19 vaccine. However, many people who have been vaccinated have also become infected. Niklas Bobrovitz, DPhil, student in the MD program at the University of Toronto’s Temerti Faculty of Medicine told Helio.


“We want to better understand the protection of people from the vaccine and previous infection, called hybrid immunity, to help inform vaccine policy,” Bobrovitz said.

Bobrovitz and colleagues performed a systematic review and meta-regression during which they searched MEDLINE, Embase and Web of Science for cohort, cross-sectional and case-control studies, among other large databases, from January 1, 2020 to June 1. , 2022, using keywords related to SARS-CoV-2, re-infection, protective efficacy, previous infection, presence of antibodies and hybrid immunity.

According to the study, the main outcomes were the protective efficacy of hybrid immunity against re-infection and hospitalization or severe disease, hybrid immunity relative to previous infection, hybrid immunity relative to previous vaccination and hybrid immunity relative to hybrid immunity at lower vaccine doses. .

In total, 11 studies reporting protective efficacy of previous SARS-CoV-2 infection and 15 studies reporting protective efficacy of hybrid immunity were included in the final analysis. For hybrid immunity, there were 153 estimates available.

The researchers determined that the effectiveness of the hybrid vaccine against hospitalization or serious illness was 97.4% (95% CI, 91.4%-99.2%) for the primary vaccine series and 95.3% (95% CI, 81.9%-98.9%). ) at 6 months with the first booster vaccination after the most recent infection or vaccination.

They also found that the efficacy of hybrid immunization against re-infection decreased to 41.8% (95% CI, 31.5%-52.8%) at 12 months after primary series vaccination, while the efficacy of hybrid immunization decreased to 46.5% (95%) after the first booster vaccination. . CI, 36%-57.3%) at 6 months.

For prior infection alone, there were 97 estimates, on the basis of which the researchers found that the effectiveness of prior infection against hospitalization or serious illness at 12 months was 74.6% (95% CI, 63.1%-83.5%), while the effectiveness of prior infection at 12 months was Infection against decreased to 24.7% (95% CI, 16.4%-35.5%).

Niklas Bobrovitz

Based on these findings, Bobrovitz said there is a “significant benefit” to getting vaccinated even after a previous COVID-19 infection, and that periodic booster vaccinations can help maintain protection against severe disease and future infections.

Bobrovitz added that people should not be intentionally infected with COVID-19 to acquire hybrid immunity.

“You can die, be hospitalized, suffer from Covid for a long time, or pass the virus on to a vulnerable person,” Bobrovitz said. said “If you’re lucky enough not to have been infected yet, continue to follow public health guidelines and get the vaccines you’re eligible for.”

In a related commentary published in Lancet Infectious Diseases, Viviane S. Boaventura, MD, PhD, of LIB and LEITV laboratories in Gonçalo Moniz InstituteAnd colleagues wrote that after the first 2 years of the global vaccination campaign and nearly a year with omicron subvariants causing high rates of global infection, the focus of first-generation vaccines should be prevention of severe disease.

“We are currently facing a new wave of omicron subvariants. While awaiting data on the efficacy of bivalent and other next-generation vaccines, the gold standards against COVID-19 remain both non-pharmacological strategies to prevent SARS-CoV-2 infection and prevent severe disease, ” wrote Boventura.

Bobrovitz N, et al. Lancet Infect Dis. 2023; doi:10.1016/S1473-3099(22) 00801-5.


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