Antibodies in recovered patients decrease rapidly
The levels of antibodies found in patients recovered from Covid-19 decreased rapidly two to three months after infection in symptomatic and asymptomatic patients, according to a Chinese study, which raises doubts about the duration of immunity against the new coronavirus.
The research, published in the scientific journal Nature Medicine on June 18, emphasizes the risk of using Covid-19 “immunity passports” and justifies the prolonged use of public health interventions such as social detachment and isolation of groups high-risk, researchers said.
Health officials in some countries, such as Germany, are debating the ethics and feasibility of allowing people who have had a positive antibody test to move more freely than those who have not.
The survey, which studied 37 symptomatic and 37 asymptomatic patients, found that, of those who tested positive for the presence of IgG antibodies, one of the main types of antibodies induced after infection, more than 90% showed sharp declines within two to three months.
The average percentage of decline was over 70% in symptomatic and asymptomatic patients.
For serum neutralizing antibodies, the average percentage of decline in symptomatic individuals was 11.7%, and in asymptomatic individuals it was 8.3%.
The study was carried out by researchers at Chongqing Medical University, a branch of the China Disease Control and Prevention Center and other institutes.
Jin Dong-Yan, a professor of virology at the University of Hong Kong who was not part of the research group, said the study did not deny the possibility that other parts of the immune system could offer protection.
Some cells memorize how to deal with a virus when they are first infected and can provide effective protection if there is a second round of infection, he said. Scientists are still investigating whether this mechanism works for the new coronavirus.
“The discovery in this study does not mean that the sky is collapsing,” said Dong-Yan, noting that the number of patients studied was small.
This article is available in: Português