Study suggests coronavirus immunity drops after 3 months

Findings stemmed from finger prick tests researchers said

Asked about herd immunity, Prof Ward said: "Even at best, (in the first round of the study) 94 percent of the population remained not likely protected, and now that has declined to over 95 percent of the population who don't have evidence of antibodies".

Scientists at Imperial College London tracked antibody levels in the British population following the first wave of COVID-19 infections in March and April.

Derek Hill, a professor of medical imaging science at University College London, also noted that the study's findings could not be entirely reliable, since they did not compare before and after scores, and involved a large number of people who self-reported having had COVID-19, who had no positive test.

The finger pricks tested for coronavirus antibodies, and results revealed a drop from almost 6% to 4.4% over a three-month span, which researchers said translates to a 26.5% decline. People infected once have antibodies that can be detected for many years after infection.

Younger people who had recovered from Covid-19 had a slower loss of antibodies, compared to people older than 75 who had survived an infection, the researchers found.

The number of people with antibodies fell by a quarter, from 6% of the population in June to 4.4% in September, according to a study which included some 365,000 United Kingdom residents.

Researchers warned, however, that it remains unclear whether antibodies provide any effective level of immunity or, if such immunity exists, for how long it might last.

The idea that COVID-19 herd immunity can be achieved naturally, by a large proportion of the population contracting the virus, has been debunked by a United Kingdom study showing that coronavirus immunity is short-lived. The samples were not taken from the same people over and over again, but from different people over time. As for the effectiveness of vaccines, the researchers say a vaccine may be more effective than a real infection in offering protection against the coronavirus. "We don't yet know whether this will leave these people at risk of reinfection with the virus that causes COVID-19, but it is essential that everyone continues to follow guidance to reduce the risk to themselves and others".

Earlier national prevalence surveys that determined how many people have had Covid19 in Iceland recorded a durable antibody response over four months from the time of infection.

Another separate arm of the REACT study is now monitoring levels of current infection in the United Kingdom using at-home swab tests, involving over 150,000 people every month.

The study found there was no change in antibody positivity in healthcare workers between June and September. "If someone tests positive for antibodies, they still need to follow national guidelines including social distancing measures, getting a swab test if they have symptoms and wearing face coverings where required", he said.

Doctors are anxious because more and more people are reporting similar symptoms, which can include memory loss, confusion, difficulty focusing, dizziness, and trouble speaking.

"This study is really like the first piece of the puzzle that actually gives us the indication that, yes, these antibodies don't seem to stick around for everybody", Hoyen said.

"So I think we are a long, long way from any idea that the population will be protected by other people".