TORONTO – As vaccination proceeds in full swing, Ontario has decided what to do with AstraZeneca. The problem is that just under half a million doses produced by the Anglo-Swedish consortium will have to be used by the end of the month, with the deadline set for 31 May.

There is still no certainty on this controversial issue. On the one hand, the provincial government has suspended the administration of the first dose of AstraZeneca in light of the risks of thrombosis, which in Canada have led to 28 serious cases and 3 deaths. But health minister Christine Elliott reiterated once again that not a single dose of vaccines that have been delivered in recent months would be wasted in Ontario. As a result, the most likely hypothesis is that health authorities will give the green light to the use of AstraZeneca for those who have already received the first dose of this vaccine.

But the already complicated situation is even more tangled if we move to the federal level. And that’s because Theresa Tam, Chief Public Health Officer of Canada, said as recently as Wednesday that the prevailing indication for those who have already had the first dose of AstraZeneca is to proceed with the second dose using another vaccine Pfizer or Modern.

To ensure the safety and effectiveness of the mix of two different vaccines, we find a British study presented at the beginning of May, a second Spanish study published earlier this week and a consensus in the world scientific community. In addition to this, an all-Canadian study has begun to check that the mix of two vaccines guarantees those who receive doses to develop an adequate immune response against Covid-19.

In Ontario, therefore, those who have already received the first dose of AstraZeneca will be able to freely decide whether to have a second dose of the same vaccine – with the incentive to receive it before the scheduled time of the provincial government, about a couple of months – or opt for a second dose of Pfizer or Moderna.

  Meanwhile, the mass immunization campaign continues. Yesterday in Ontario, according to covid19tracker.ca, a total of 144,986 doses were administered: in total, of the 8,611,345 doses delivered by federal authorities, 7,576,624 doses were administered in the province.

After a first period in which priority was given to the vaccination of older people, with a progressive lowering of the limit age to receive the vaccine, in Ontario, all adults can book the appointment for vaccination against Covid-19 through the provincial portal. Starting May 31, all children aged 12 to 16 will be vaccinated, although some areas of the province have already begun the immunization campaign for adolescents. In Toronto in recent days, temporary clinics have been in place for boys of that age group, while since yesterday, reservations for appointments for vaccines for adolescents from 12 to 15 years old have been opened throughout the Peel Region.