appears to be converging on 0.5–1.0%.It is, therefore, important to establish whether individuals who have contracted the virus once can contract it again and become contagious, or whether they are immune to future infection.Stay informed with live updates on the current COVID-19 outbreak and visit our coronavirus hub for more advice on prevention and treatment.“In the absence of a protective vaccine, it is critical to determine if exposed or infected people, especially those with asymptomatic or very mild forms of the disease who likely act inadvertently as the major transmitters, develop robust adaptive immune responses against SARS-CoV-2,” says Marcus Buggert, an immunologist at the Karolinska Institutet in Solna, Sweden.Research.