As per a study conducted in Britain on 100 Covid patients who were not hospitalized, it was observed that they had developed ‘cellular immunity’ to the SARS-CoV-2 virus. Even patients who had a mild Covid infection exhibited this immunity.
These patients were healthcare workers who had antibody responses in March and April after the Covid infection. This is suggestive that Covid-19 patients, even asymptomatic ones, might be protected against the infection. But there were rare cases when recovered Covid patients have been infected again. The instances of re-infection of Covid-19 were very few worldwide.
The study is still not clear on the extent of the immunity, in terms of strength and duration. But it could throw light on understanding Covid-19 immunity. It could aid the study of other Sars-CoV-2 infections and their chances of recurrence.
Blood samples of about 100 Covid patients were taken each month for about 6 months after they recovered from the infection. An analysis of the blood samples revealed a robust T-cell response, an indicator of good response. Some patients had reduced antibody levels. The T-cell response was more with those patients who suffered symptomatic Covid-19 as against those who were symptomatic. When a viral infection strikes the body, it is resisted by the immune system.
When there is a stronger infection, T-cells and B-cells join the fight. The T-cells stimulate the B-cells to produce antibodies. The antibodies immobilize the virus from entering the body cells. The study seeks to examine who long the antibodies will provide the safety factor to the body. The T-cells in recovered patients were nearly 50% more than those who didn’t experience any symptoms.
T-cells survive for a long period of time and so it would be interesting to watch the kind of immunity they offer the recovered patients. The study may need to be extended to a larger population to understand the working of the T-cells against Covid-19 better.
While this could indicate that symptomatic recovered patients had protection against a possible second infection; it could also mean that the asymptomatic recovered patients recovered easily sans greater immune response. In the battle against Covid-19, immunity testing by checking antibodies levels has been an area of focus.
A test has been developed for detecting T-cells in the patient blood samples. The far-reaching consequences of the T-cell response against the Coronavirus have to be understood. Since T-cells precede antibody response in the body, testing for T-cells can be a better indicator of having been infected with Covid-19.
In another study, it was found that some recovered patients of Covid-19 have tested positive for T-cells but negative for antibodies. Antibody test results are available within 90 minutes. On the other hand, tests for T-cells take a few days. The study was correlated by also testing a few persons who didn’t have Covid-19. The purpose of these studies is to provide a clearer picture of vaccine development.