People who are homeless have high rates of COVID-19 reinfection, putting the health of an already vulnerable population at further risk, a study published Friday in the BMC Infectious Diseases journal says.

Homeless people in Toronto who had COVID-19 were more than twice as likely to get it again as people who had housing, said lead author Lucie Richard, a senior research associate at the MAP Centre for Urban Health Solutions at St. Michael’s Hospital.

The higher rates of reinfection are likely due to increased exposure to the virus as homeless people are “forced to reside in congregate, crowded shared settings which are rife with transmission,” Richard said.

They are also more likely than the general public to have underlying health conditions that make them more vulnerable to illness, she said.