Canada’s chief public health officer Dr. Theresa Tam outlined new guidance released by the National Advisory Committee on Immunization (NACI) Friday on COVID-19 vaccine booster shots. In the guidance, the NACI recommends adults aged 80 and older, and seniors in long-term care, be offered a booster dose at least six months after receiving their second dose. Certain other high-risk populations may also be offered a booster dose, according to the guidance.