An infectious disease expert explains new federal rules on ‘mix-and-match’ vaccine booster shots Posted byGlenn J Rapsinski October 22, 2021 Leave a comment on An infectious disease expert explains new federal rules on ‘mix-and-match’ vaccine booster shots As boosters are authorized for all three COVID-19 shots available in the US, the ability to swap out vaccine types looks to be a boon to the immune system.