News Ontarians can safely take AstraZeneca as second dose, MOH SHARE ON: Mo Fahim, staff Friday, Jun. 18th, 2021 Credit AstraZeneca.com Ontario will continue using AstraZeneca’s COVID-19 vaccine as a second dose. This comes in light of new guidance from the National Advisory Committee on Immunization suggesting using an mRNA vaccine from Pfizer and Moderna over AstraZeneca because of improved immunity and less risk of a rare blood clot. In a statement released Friday, a spokesperson for the Ministry of Health confirmed that if you had AstraZeneca as a first dose, you can safely take any of the three available vaccines for your second shot. The spokesperson says if you choose to take an AstraZeneca second dose you can be assured it will provide good protection against infection and very good protection against severe illness and hospitalization.