Coronavirus antibodies dropped by nearly 26 percent in the three months following infection, according to a new REACT2 study.
The research, published on Tuesday, surveyed a total of nearly 365,000 British adults from June through September. Almost 17,500 people in that group who tested positive for COVID-19 showed a decline in the presence of antibodies across all age groups.
“We know seasonal colds can reinfect people every six months,” Wendy Barclay, head of the infectious disease department at Imperial College London, told Politico, noting that the coronavirus appears to follow a similar trend.
Rates at which the antibodies decreased over time varied, according to Politico. Cases in which the infected person was asymptomatic showed a rapid drop, while younger people had high levels of antibodies and a slower decline and older people had lower levels of antibodies from the beginning.
“We don’t yet know what level of antibody is needed in a person’s blood to prevent reinfection,” Barclay said.
The Centers for Disease Control and Prevention (CDC) backtracked on earlier guidance that said the coronavirus had a three-month window of immunity following infection.
“People can continue to test positive for up to 3 months after diagnosis and not be infectious to others. Contrary to media reporting today, this science does not imply a person is immune to reinfection with SARS-CoV-2, the virus that causes COVID-19, in the 3 months following infection,” the CDC said in a press release in August.
Despite this, German virologist Christian Drosten believes that antigen testing could still be useful in combating COVID-19.
“We could develop a working hypothesis in public health,” he said, according to Politico. “A negative result of [an] antigen test predicts a waning of infectability in a patient.”