The novel coronavirus SARS-CoV-2 was first identified in December 2019 and is now responsible for over 9.2 million cases of Covid-19 worldwide (correct as of 24 June 2020). But currently, the long-term immune response, and whether exposure protects against future infection, is unknown.

This recent lab note highlighted an interesting study in Cell which reported that non-hospitalized patients who have recovered from a mild COVID-19 infection carry T cells that target SARS-CoV-2. T cell responses may provide better routes for immunity and vaccine development than the other ‘arm’ of the immune system — the B cell response — even though the latter response has received far more attention to date than T cells. 

B cells produce antibodies which are important in immune system recognition and memory of features of pathogens called antigens. Antibody testing is increasing, enabling identification of individuals who have been asymptomatically infected with SARS-CoV-2. 

A key question remains: are people with antibodies immune from reinfection? A June study in Nature Medicine has addressed the antibody response of asymptomatic patients. The researchers reported that their antibody levels begin to decrease 2-3 months after infection, and that they exhibited a weaker immune response to infection compared to symptomatic patients. Therefore, we certainly shouldn’t depend on the idea that having antibodies for SARS-CoV-2 means that a person is immune. Allowing recovered patients to resume their normal lives without masks and social distancing is not as simple as first thought.

Our knowledge about the novel coronavirus is rapidly expanding. It remains unknown whether the T cell or B cell response actually provides long-lasting, or any, immunity to reinfection with SARS-CoV-2. But, studies such as these are fundamental in our continued understanding of this disease and will certainly be important knowledge for vaccine development and continued social distancing strategies.