Article content continued
Most of Naylor’s colleagues are taking a pragmatic approach, he said, aligning with Canada’s National Advisory Committee on Immunization (NACI), as well as a World Health Organization scientific group, both of which have decreed doses can be stretched to 42 days apart in exceptional circumstances — severe shortages, for example.
The concern? While the first dose is considered protective, though not fully, it’s not known how long that protection lasts, a worry given the variants and the potential for creating “made-in Canada mutants,” Naylor said. The second shot also provides a dramatic boost in immune response.
On the other hand, given the grim supply shortages some provinces find themselves with, slight delays — going out to six weeks — may be necessary, now and then, to manage supply chain wobbles and avoid holding back large numbers of shots that could cost many vulnerable lives, Naylor said. In the Pfizer trial some people received their second dose as early as 19 days, and as much as 42 days after the first.
De-prioritize the infected
“There’s no contraindication to immunizing people who have had a past COVID-19 infection,” Naylor said. However, the federal vaccine advisory group has said that, with limited supply, “initial doses may be prioritized” for those who have not had a previously confirmed SARS-CoV-2 infection.
That could be a logistical nightmare: How do you screen everyone for antibodies to the virus before agreeing to inoculate them? Do we do serological testing on every single person we’re trying to register for a vaccine? Think about the rollout thus far, Smith said. It could slow down the process further.