All You Wanted to Know About Covid-19 Immunology but Were Afraid to Ask

Dr Zania Stamataki, a viral immunologist, has provided a useful overview of our growing but, as yet imperfect, understanding of the serological (blood) responses to a Sars CoV-2 infection (https://www.theguardian.com/commentisfree/2020/jun/25/viral-immunologist-antibody-tests-covid-19-immuity-coronavirus). She points out that blood tests (easy to take) can vary in accuracy (infections with other coronaviruses, such as the common cold, can produce false positives). Serological tests tell us, however, more about the incidence and transmission of the virus than do PCR screenings.  These genetic tests detect the actual virus but require much greater sampling skill (relying on nose and throat swabs). Dr Stamataki notes that it is difficult to detect antibodies in the bloods of newly infected people but that most patients develop these protective proteins in 1-3 weeks. She also points out that these tests can warn us about high risk groups. For example, one hospital study showed that a higher percentage of (less protected) housekeeping staff developed an infection than was seen in (more protected) staff working in intensive care. Dr Stamataki also illustrates what we are learning about the roles of the B cells (that produce antibodies) and the T cells (that can, for example, destroy infected cells) in Sars CoV-2 infections. In the case of the B cells, we don't know yet how long antibody protection lasts, whether booster doses of vaccine might be required or even whether we will need new vaccines as the virus mutates. T cell responses are evident in most Covid-19 patients, even when there are no detectable antibodies in their blood. There is also a possibility that T cell memory of Sars CoV-2 infections lasts longer antibody memory. Studies appear to show that asymptomatic (without symptoms ) and presymptomatic (at the very start of an infection) can be highly contagious. Waiting for symptoms can be leaving it too late but there might be early T cell indicators of infection. Dr Stamataki appears optimistic about the early vaccine studies suggesting that immunological memory is a possibility. The account, however, emphasises that we are having to learn a lot about the body's response to this novel (for humans) virus under very difficult circumstances.