Alluvion Health is preparing to host another vaccination clinic Alluvion Health is preparing to host another vaccination clinic and last updated 2021-05-14 11:17:13-04 GREAT FALLS â With people as young as 12 now eligible to receive Pfizerâs COVID vaccine, Alluvion Health in Great Falls is preparing to host a vaccine clinic. Alluvion plans to partner with the Cascade City-County Health Department to offer vaccines to people from 2 p.m. until 7 p.m. on Friday, May 21 at the Montana ExpoPark. They expect to have least 1,500 doses available. The Pfizer vaccine is given in two shots. People who receive their first shot at the May 21st event will receive their second shot on Friday, June 11th.