FARGO, N.D. (AP) — A dominant health system in the Dakotas that bills itself as one of the largest health organizations in the country is making COVID-19 vaccinations mandatory for all its employees, citing the spread of more contagious variants.

Sanford Health is requiring all workers to get shots by Nov. 1. More than 90% of clinicians and 70% of nurses in the organization are already fully vaccinated. Sanford has 46 hospitals, 1,500 physicians and more than 200 Good Samaritan Society senior care locations in 26 states and 10 countries.

It is based in Sioux Falls, South Dakota, and has major medical centers in Fargo and Bismarck, North Dakota, and Bemidji, Minnesota.