A study has revealed that people who have recovered from a severe COVID19 infection have a long-lasting immune response against the SARS-CoV-2 virus. This study has been done by experts from the Massachusetts General Hospital. New research gives some hope that people who have survived a severe COVID19 infection will have enduring protective antibodies to keep the reoccurrence of the disease at bay. Experts have said that assessing antibodies can be a precise tool to track the transmission of the virus as well. Experts have not been able to determine how long these antibodies can last until now. The senior author of the study, Dr. Richelle Charles, and her colleagues have studied the blood samples of 343 patients who have been diagnosed with severe COVID19 infection. In the study, the blood samples of the patients have been extracted up to four months after patients have started showing symptoms. This study has been published in Science Immunology.
Experts have applied these blood samples on laboratory plates layered with the receptor-binding domain (RBD) of the virus’s spike protein. The virus’s spike protein binds to the surface of the cell and causes infection. The study of these blood samples shows how antibodies present in the blood plasma attach to RBD. The findings of the research have been compared with blood samples taken from more than 1500 people before the COVID19 pandemic. Scientists have revealed that calculating the antibody called immunoglobulin (IgG) has been highly precise in tracking patients with the disease who have been showing symptoms for at least 14 days. The senior author of the study has said that since the nasal swab test for COVID19 infection has lost its sensitivity with time, replacing it with an antibody test for the patients who have been showing symptoms for at least eight days will help to spot some positive cases, which have been missed.
Experts have found that there have been elevated levels of IgG in these patients for four months. The IgG levels are linked with the existence of protective neutralizing antibodies. It has shown a little decrease in activity over time as well, which means such patients will be protected for a particular time span. The study has found two other protective antibodies as well, immunoglobulin A (IgA) and immunoglobulin M (IgM). These antibodies live up to two and a half months or less in the bodies of the patients who have recovered from a severe COVID19 infection. Experts clearly state that if a person who has recovered from the disease and has IgA and IgM antibodies, he or she is likely to be diagnosed with COVID19 again within the last two months of recovery.