Antibodies against the novel coronavirus may "disappear quickly" following recovery, says a new study which assessed more than 250 COVID-19 patients up to five months post-infection. The study, published in the journal Science Immunology, analysed 983 blood plasma samples collected from 79 hospitalised COVID-19 patients and 175 outpatients and asymptomatic people infected with the SARS-CoV-2 virus. According to the scientists, including Katharina Roltgen from Stanford University in the US, the IgG antibodies likely persist for longer, but also showed a slow decline even in severely ill patients who mounted very strong initial immune responses.
Based on the findings, the researchers said the levels of different types of antibodies which neutralise the coronavirus "all begin to decrease in patients after approximately the first month post-onset of symptoms." They found a higher ratio of antibodies that react to the viral spike protein complex in patients with mild illness compared with severely ill patients.
"The decline in antibody titers is most evident in individuals who had asymptomatic infection or mild illness, who produce lower levels of antibodies at the peak of their responses," the scientists wrote in the study. They believe the findings may raise important questions about the reliability of seroprevalence studies, since the rapid waning of antibody levels in people may lead to an underestimation of how many people may have been previously infected in a given population. "The decrease in antibodies after infection also raises the question of how long antibodies elicited by vaccination will last, and whether frequent boosting will be needed to maintain protection," the scientists noted.