Asking people to switch for 2nd dose seems premature

Re Why did Canada ‘switch up the script’ on second doses of the AstraZeneca vaccine? Here’s what we know, June 17

While the VITT risk is a valid reason to stop giving AstraZeneca as a first shot, strongly recommending that people switch to something different for the second seems premature.

The data on which NACI based its advice involved less than 2,000 people across three different studies. The VITT problem with AstraZeneca only came to light after millions of doses had been administered. Similarly, the possible link between Pfizer and myocarditis and pericarditis among young people, especially males, did not appear in trials. At this point, switching looks like taking an as-yet unknown possible risk instead of a well-documented known one. Patricia Wilmot, Toronto