Study says natural immunity from Covid offers same protection as vaccination

The latest study on Thursday (February 17) said that protection against Covid from being previously infected lasts at least as long as that offered by vaccination. The study published in the Lancet Journal said that 10 months after getting Covid, people still had an 88 per cent lower risk of re-infection, hospitalisation and death. This made natural immunity at least as durable, if not more so than two doses of Pfizer or Moderna's vaccines against the virus.

"Although protection from re-infection from all variants wanes over time, our analysis of the available data suggests that the level of protection afforded by previous infection is at least as high, if not higher than that provided by two-dose vaccination using high-quality mRNA vaccines," the study, led by the Institute for Health Metrics and Evaluation (IHME) said. The researchers reviewed 65 studies from 19 countries up to September last year, which would mean some studies covered the period when infections of the Omicron variant were seen.

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Omicron proved to be more contagious than previous strains, but less severe.

"Our meta-analyses showed that protection from past infection and any symptomatic disease was high for ancestral, alpha, beta, and delta variants, but was substantially lower for the omicron BA.1 variant," Thursday's study said. Sharing the findings, the study said that pooled effectiveness against re-infection by Omicron BA.1 variant was 45.3 per cent, and 44 per cent against omicron BA.1 symptomatic disease.

It added the mean pooled effectiveness was greater than 78 per cent against severe disease (hospitalisation and death) for all variants including Omicron BA.1. The protection from re-infection from ancestral, alpha and delta variants declined over time but remained at 78.6 per cent at 40 weeks. But the protection against re-infection by Omicron BA.1 declined more rapidly and was estimated at 36.1 per cent at 40 weeks.

Thursday's study also pointed out that protection against severe disease remained high for all variants with 90.2 per cent for ancestral, alpha, and delta variants and 88.9 per cent for Omicron BA.1 at 40 weeks.

Caroline Stein of the IHME, who is a co-author of the study, said in a statement that vaccines continue to be important for everyone to protect high-risk populations such as those who are over 60 years of age and those with comorbidities, news agency AFP reported on Friday.

Meanwhile, Cheryl Cohen, an epidemiologist at South Africa's National Institute for Communicable Diseases, said that in the long run, most infections would occur in people with strong protection against severe disease because of previous infection, vaccination, or both. "These results suggest that similar to other human coronaviruses, there might be a low seasonal hospitalisation burden," Cohen added.

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