When rescheduling, people can choose a different vaccine for their second dose, but the province recommends people who received a first dose of AstraZeneca get Pfizer or Moderna for their second dose.“This recommendation is based on emerging evidence of a better immune response with an alternate second dose and the risk of rare but serious blood clotting events associated with AstraZeneca,” the province stated.Rescheduling notices for second dose appointments will continue to be sent over the coming weeks. .