COURTESY HT JULY 23

Covid antibodies fade fast, raising risk of reinfection’
Bloomberg

letters@hindustantimes.com

Washington : Recovering from Covid-19 may not offer much protection from future infections for those with only a mild case, according to a report that suggests caution regarding so-called herd immunity as well as vaccine durability.

The correspondence in the New England Journal of Medicine outlined an analysis of antibodies taken from the blood of 34 patients who had recovered after suffering mainly mild symptoms that didn’t require intensive care.

The first analysis was done on antibodies taken an average of 37 days after symptoms began, with a second after about 86 days, or less than three months.

The researchers found that antibody levels fell quickly, with a half-life of about 73 days between the two-time frames. The loss of antibodies occurred more quickly than with SARS.

The antibody response is being studied by scientists for indications of how long-lasting immunity may be. While there’s little evidence to suggest reinfections are occurring, health experts have yet to pin down specifics.

The findings raise concern that protection from reinfection may not last long in those with mild symptoms, which accounts for the majority of cases.

Further studies will be needed “to define a quantitative protection threshold and rate of decline of antiviral antibodies beyond 90 days”, according to the researchers led by F Javier Ibarrondo, from David Geffen School of Medicine at the University of California Los Angeles. The brief report was in the form of a correspondence published in the journal