Australia will eventually move to a heterologous COVID-19 vaccination regimen if the evidence firms up, a leading infectious diseases specialist predicts.

Associate Professor Paul Griffin has responded to the weekend news that Canadian health authorities have recommended people who have received a first dose of AstraZeneca’s vaccine should have an mRNA shot as their second dose.

The decision is “based on emerging evidence of a potentially better immune response from this mixed vaccine schedule and to mitigate the potential risk of vaccine-induced thrombosis with thrombocytopenia associated with viral-vector vaccines”, Canada’s National Advisory Committee on Immunization says.

In Australia, GPs have been tasked with completing vaccination for 815,000 people aged 50-60 who have received one dose of the AstraZeneca vaccine but may be hesitant to get a second dose because of the perceived risk of thrombosis with thrombocytopenia syndrome (TTS).