New Delhi, August 23
High levels of exposure to the SARS-CoV-2 virus may reduce or overcome the protection that Covid-19 vaccination and prior infection provides, according to a study conducted in the US.
The findings, published recently in the journal Nature Communications, suggest that in densely crowded settings, control measures that reduce levels of exposure to the virus — such as masking, improved ventilation, and distancing — may afford additional benefit in preventing new infections among people who have been vaccinated or previously infected.
The study was performed to understand whether the immunity gained after vaccination or a prior infection was less effective or “leaky” in situations where people are exposed to high levels of the virus.
“It’s really hard to find a population, such as the residents of the Connecticut Department of Correction, where we know the type of exposure somebody has and we know their vaccination and prior infection status,” said Margaret Lind, lead author of the research paper, and an associate research scientist at Yale University, US.
The researchers tracked infections among 15,444 residents of Connecticut correctional facilities between June 2021 and May 2022, when the state experienced two epidemic waves due to the emergence of the Covid-19 Delta and Omicron variants.
They also determined which people had resided with a Covid-19-positive cellmate and, as a result, had high exposure to the Covid-19 virus.
The study found that during the Delta and Omicron epidemic waves, immunity acquired after a vaccination, prior infection, and both vaccination and infection (hybrid immunity) was weaker when residents were residing with an infected inmate.