Prior infections survive severe COVID, regardless of variant

A meta-analysis of 65 studies found that prior SARS-CoV-2 infection provided strong protection against severe disease from subsequent reinfection, with little difference between strains. , a previous Omicron BA.1 infection provided poor protection against another reinfection.

Stephen Lim, MD of the Institute for Health Metrics and Evaluation, reported that protection against hospitalization and death was 90.2% for ancestral, alpha, and delta variants and 88.9% for Omicron BA.1 at 40 weeks, and 88.9% for all variants. remained high. (IHME) and the University of Washington School of Medicine, Seattle, and lancet.

The pooled mean efficacy against reinfection or symptomatic reinfection was >82% for the pleomicron strains compared to approximately 45% for the Omicron BA.1 variant.

Protection from reinfection from pre-Omicron strains decreased over time, with 78.6% at 40 weeks compared to 36.1% with Omicron BA.1.

“Our analysis suggests that the level of protection from previous infection by the variant and over time is at least comparable, if not greater, than that provided by the two-dose mRNA vaccine. We are doing it,” Lim and colleagues wrote.

These data will influence future guidance on when to get booster doses, they added. I support the idea that people should be treated in the same way as other people.”

“However, the protection from previous infections compared to that conferred by vaccination must be weighed against the severe morbidity and mortality risks associated with the initial infection,” they noted. This risk balance varies by variant type: Omicron is less severe than Delta, for example, and there are other individual-related risk factors such as age and other comorbidities.”

In a press release, IHME co-author Caroline Stein, M.D., Ph.D., said, “Decision makers need to consider both innate immunity and vaccination status to get a complete picture of an individual’s immune profile. There is,’ he said.

Protection weakens over time

The findings provide insight into how protection from past infections weakens over time, especially for the latest variants.

This is a testament to Omicron’s immune escape function, Lim and team noted.

and accompanying commentsDr. Sherrill Cohen of the National Institute of Infectious Diseases, Johannesburg and Dr. Juliet Pulliam of Stellenbosch University, South Africa, said, “Currently, in most parts of the world, COVID-19 is dominated by various omicron substrains. , continues to emerge with new substrains that demonstrate the importance of potential immune escape.”

“The high and sustained levels of protection conferred by previous infections against serious illness have important implications for COVID-19 vaccine policy,” they wrote. In 2006, the global SARS-CoV-2 seroprevalence was estimated at 59%, with considerable variability in the proportion of immunity induced by infection or vaccination in different settings.Seroprevalence in Africa The rate was estimated at 87% in December 2021 as a result of the infection.”

They also noted that SARS-CoV-2 may not be caused by the same seasonal spikes seen with influenza. “While it is not possible to predict the long-term trajectory of SARS-CoV-2 circulation with certainty, the short duration of immunity combined with the high transmissibility of Omicron subspecies and their substrains suggests that SARS-CoV-2 may not experience such dynamic resonances driving annual flu epidemics,” they noted.

“In the long run, most infections occur in people who have strong defenses against severe disease because of previous infections, vaccinations, or both,” they continued. , These results suggest that, like other human coronaviruses, there may be less seasonal hospitalization burden associated with SARS-CoV-2.”

Survey details

This systematic review and meta-analysis included 65 studies from 19 countries, including retrospective and prospective cohort studies and negative case-control studies published up to 31 September 2022. I was.

A study that showed results on the protective effects of innate immunity in unvaccinated individuals compared with those who were unvaccinated and COVID-naive showed that individuals with controlled vaccination status was included as well as the containing studies. Studies involving hybrid immunization were excluded.

Overall, there is a paucity of available studies, particularly studies examining the time from infection to severe disease and reporting on Omicron BA.1 variants and substrains. , Lim and team points out.

Additionally, we found evidence of publication bias in 3 of the 13 variant outcomes. Because the researchers relied on observational studies, there was a risk of remaining confounding.

Furthermore, the approaches to ascertain past infection status varied between studies.