COVID-19 pandemic. Herein, we discuss experiences and open questions about the
complex immune responses to SARS-CoV-2. Some people react excellently without
experiencing any clinical symptoms, they do not get sick, and they do not pass the virus on
to anyone else (“sterilizing” immunity). Others produce antibodies and do not get COVID-19
but transmit the virus to others (“protective” immunity). Some people get sick but recover. A …