A preprint study published Tuesday by researchers in England suggested that the prevalence of Covid-19 antibodies in the British population was waning, prompting scary headlines about short-lived immunity to the coronavirus. Antibodies are molecules produced by the immune system that play a key part in preventing future infections, but their role in Covid-19 isn’t totally understood, and it’s not known how long they last in the body.
The British study, called REACT (that’s short for Real-time Assessment of Community Transmission), was led by researchers at Imperial College London. It involved sending out finger-prick tests to detect antibodies to randomly selected people across the country over three rounds of testing between June and September. Like most other countries, England had its first big wave of Covid-19 cases in March and April, so the study aimed to find out whether people who got infected during that time were able to develop and sustain their levels of antibodies in the following months.
Tests on over 365,000 people across England showed that the proportion of participants who tested positive dropped from 6% to 4.4% between June and September — a drop of 26.5%. The decline in positivity rates varied across demographics, though: It was largest in people aged 75 and older and also larger in people who had a suspected, rather than confirmed, case of Covid-19.
“These data,” the authors conclude, “suggest the possibility of decreasing population immunity and increasing risk of reinfection as detectable antibodies decline in the population.”
It’s scary to think that immunity to Covid-19 may not last. A vaccine will not likely be widely available until the middle of next year, and a handful of confirmed reinfections have been documented. The REACT study prompted headlines referencing a study showing “waning antibody immunity to Covid over time” (Reuters) and “evidence of waning immunity to Covid-19” (CNN); a Twitter moment said Covid-19 antibodies “‘fall rapidly’ after infection.” But as I’ve learned over many months of covering Covid-19, alarming news headlines tend to come with many caveats. The experts I spoke to seemed to…