Compromised immunity can allow SARS-CoV-2 to evade the immune system The vast majority of people infected with SARS-CoV-2 clear the virus, but those with compromised immunity--such as individuals receiving immune-suppressive drugs for autoimmune diseases--can become chronically infected. As a result, their weakened immune defenses continue to attack the virus without being able to eradicate it fully. This physiological tug-of-war between human host and pathogen offers a valuable opportunity to understand how SARS-CoV-2 can survive under immune pressure and adapt to it. Now, a new study led by Harvard Medical School scientists offers a look into this interplay, shedding light on the ways in which compromised immunity may render SARS-CoV-2 fitter and capable of evading the immune system.