New research on human immune mechanisms developed in response to COVID-19 has suggested that antibodies may last for only two to three months after a person becomes infected with the novel coronavirus.
Survivors of COVID-19 have been donating their blood on the premise that others who are severely ill from the virus could benefit from infusions of plasma, a light yellow blood component.
Scientists would later embark on testing to know if the blood plasma might also prevent the infection in the first place as thousands of patients have been treated with the so-called convalescent plasma.
But a pair of new studies claim that patients lose their IgG antibodies, the virus-specific; slower-forming antibodies associated with long-term immunity, within weeks or months after recovery.
The groups included nearly 20,000 members of the general population; more than 1,600 patients hospitalised for reasons other than COVID-19; and more than 3,800 exposed medical workers.
It was found that, while almost 90 percent of COVID-19 patients had the antibodies, roughly one percent to five percent of individuals in the other groups also had the virus-specific blood protein.
In their study, the authors came to a conclusion that the remaining 10 percent of infected patients with no detectable antibodies, combined with the lack of antibodies in healthcare workers, suggest that “after SARS-CoV-2 infection, people are unlikely to produce long-lasting protective antibodies against this virus.”
In a second study published on June 18 — two days after the first — in Nature Medicine, the immune response of 37 asymptomatic patients were compared to those with severe symptoms in China.
The finding was that asymptomatic individuals reacted less strongly to infection, with 40 percent having undetectable levels of protective antibodies in two to three months after the infection.
Though the study is not on large scale, the scientists said the findings should come as a strong note of caution against the idea of “immunity certificates” for people who have recovered from the illness.
“These results are interesting and provocative. More research is needed, following large numbers of people over time,” Daniel Davis, an immunologist at the University of Manchester, said.
“Only then will we clearly know how many people produce antibodies when infected with coronavirus, and for how long.”
Akiko Iwasaki, a viral immunologist at Yale University, who was not involved in either study, told New York Times: “These reports highlight the need to develop strong vaccines.
“Because immunity that develops naturally during infection is suboptimal and short-lived in most people. We cannot rely on natural infection to achieve herd immunity.”