Scientists at Massachusetts General Hospital have confirmed that survivors of severe COVID-19 infection develop long-term immunity against the virus. This is reported in an article published in the journal Science Immunology.
The researchers analyzed blood samples from 343 patients with COVID-19, most of whom had severe symptoms. Blood samples were taken within four months after the first signs of illness appeared. Blood plasma was isolated and plated on plates coated with receptor binding domains (RBDs) of the coronavirus protein to which antibodies bind. Scientists looked at how different types of antibodies in patients' blood bind to RBD and compared this to blood samples from 1,500 people taken before the pandemic.
It turned out that the antibody levels of immunoglobulin G (IgG) remained elevated in these patients for four months and were associated with the presence of protective neutralizing antibodies, which also showed a slight decrease in activity over time. According to scientists, those who have been ill for this period will be protected from re-infection.
Immunoglobulin A (IgA) and immunoglobulin M (IgM) were relatively short-lived and declined to low levels in about two and a half months or less.
The results support the use of antibody testing to track the spread of COVID-19 and detect outbreaks.