New urgency to questions about second COVID shot

The vaccination debate has moved on. It had focused on ensuring that as many people as possible got one shot of a recognized vaccine. It is now zeroing in on the second shot.

Specifically: Who is eligible for a second shot? Who gets priority? Which vaccines will be used for second shots? Should second shots be held back until all Canadians — including children — have had a chance to get their first shots?

All of these questions have developed a new urgency. Until now, governments and their experts were able to ignore them. Officially, governments have supported the notion that certain vaccines, including those manufactured by Pfizer and Moderna, require two shots.

But in practice, the second shot was treated as an afterthought — a nuisance that could be put off or ignored without causing anyone harm.

Indeed, governments unilaterally overruled the recommendations of Pfizer and Moderna that second shots of their product be delivered within three to four weeks of the initial vaccination.

Instead, the politicians decreed — on the basis of virtually no clinical evidence, but with the agreement of most of their experts — that the second shot could be delayed for up to 16 weeks.

The unstated assumption was that in the event of a showdown, the first shot mattered far more.

That assumption is beginning to change. In part, that’s because more people have received their first dose. But in part it’s because there is a belated recognition that, for some vaccines, the second shot can matter quite a bit in providing immunity from the COVID-19 virus.

All of this has served to focus attention on the second shot, particularly in light of new evidence that the AstraZeneca vaccine can cause dangerous blood clots.

Until this week, Ontario and other provinces had been promoting AstraZeneca hard — for both the first and second shots.

Now, the blood clot news has led Ontario and several other provinces to stop offering AstraZeneca as a first shot.

But as a second shot? Most provinces have not yet decided. Ontario is waiting for the results from clinical trials in the United Kingdom that are trying to determine whether AstraZeneca can be replaced by another vaccine for the second shot.

Those results are due in June. Certainly, the political pressure will be high to let provinces mix and match when it comes to second shots. People can and will argue that it is unfair to require those who still need a second dose to get it from AstraZeneca — just because that was the source of the first shot.

But who will have priority? If a second dose of, say, the Pfizer vaccine becomes available, should it go — as planned — to someone who received Pfizer on the first round? Or should it go to an AstraZeneca recipient deemed for some reason to be more worthy?

These questions have been complicated by the decision to extend vaccination to children.

Ontario wants children age 12 and over to have two shots by the fall.

But again, who will get preference? Will children automatically be moved to the front of the line when it comes to second shots? What happens to those adults who are bumped out of the queue?

All of these questions may be deemed moot if Canada ends up awash in second shots from Pfizer and Moderna. But if history is any guide, such a scenario is most unlikely.

More likely is the possibility of continued confusion. We had been fussing over who gets the first shot. We are now readying ourselves to tussle over who gets the second.