The presence of antibodies, the body’s natural response to fighting off a virus, is a positive sign in COVID-19 patients. They have become essential in the fight against the virus, but scientists still know little about the human antibody response to SARS-CoV-2.
A study suggests that these antibodies may only remain in the body for a few months, calling the immunity of a recovered person into question.
The majority of individuals who have COVID-19, symptomatic and asymptomatic, will naturally develop antibodies to fight off the virus. The Center for Disease Control (CDC) does not know if the presence of SARS-CoV-2 antibodies can protect from reinfection, nor do they know how long this protection may last.
A new study suggests that these antibodies may only last in the body up two to three months, mainly in those who were asymptomatic. The study compared a small pool of 37 recovering asymptomatic carriers to 37 recovering symptomatic carriers in the Wanzhou District of China. After two months of recovery, antibody levels dropped to below detectable levels in 40% of the asymptomatic participants, and 13% in symptomatic carriers.
Asymptomatic carriers also displayed a weakened immune response. These results may have implications for immunity strategy and serological surveys.
This study focused on antibodies and did not consider cellular immune response, which can also help fight off infection. Dr Anthony Fauci, director of the National Institute of Allergy and Infectious Diseases, said that immune responses differ between patients.
Low levels of antibodies may still help prevent reinfection, however, suggests another recent study.
“It does appear that even low levels of certain antibodies have potent neutralising capability,” wrote Dr Rasmussen, the Columbia University virologist, in the paper. “Low antibody titers don’t necessarily determine whether a patient will be protected from reinfection.”
While these results don’t necessarily confirm that a recovered patient can be re-infected, experts are wary of thinking recovered patients are permanently immune from COVID-19.
“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,” said Dr Akiko Iwasaki, a viral immunologist at Yale University.