With COVID-19 outbreaks being whipped up for a fifth year, testing has emerged as a source of frustration once again.

Whereas obtaining a test was often difficult in early 2020, now the abundance of cheaper rapid kits in grocery stores and home medicine cabinets has led to a new concern ¡ª they don¡¯t seem to work.

¡°When people tell me that their rapid antigen tests never turn positive, they¡¯re usually talking to me because they¡¯re frustrated,¡± says immunologist and epidemiologist Michael Mina.