NACI has certainly been reviewing in detail all of the emerging evidence on effectiveness in the elderly and also, as you mentioned, some immunosuppressed populations.
There are a few things that are important to establish. First, there is no correlative protection established for protection against COVID-19, as you're probably aware of. Many of these studies, the preprint studies, on certain immunosuppressed or solid organ transplant populations are based on antibody measures, and in some cases cellular responses, but not true effectiveness in the real world. It's hard to bridge those data over to real-world effectiveness. That's one thing the committee advised us in their report.
The second thing is with respect to the elderly. Much of the data that was reviewed by the committee early on in making their recommendations in fact came from long-term care settings and from the elderly. If we look at their analysis of what's been reported from the United Kingdom, where they were using an extended 12-week interval, for example, they found very good protection and very good effectiveness against severe outcomes—hospitalization and death—certainly above 80%. The effectiveness against symptomatic disease is lower, and we're seeing that reported, but the most critical outcomes are being very well protected.
Looking to Canada, the committee was reviewing presentations, as Dr. Tam mentioned, from Quebec and British Columbia. Both provinces, by the way, are doing weekly vaccine effectiveness monitoring. They're keeping a very close touch on how this is evolving. That's being fed back to NACI and the provinces and territories. We've seen in the range of 80% to 90% effectiveness in the long-term care setting in those jurisdictions, not only against severe outcomes but actually against PCR-confirmed COVID-19 infection.
It's a very strong evidence base, at this point, understanding that it's not out to 16 weeks. As Dr. Tam mentioned, we're getting up to the 10- to 12-week mark in Canada with no signs of deterioration, even in those elderly populations. The committee is watching carefully, but at this time was very comfortable to say that up to four months could be considered by jurisdictions, understanding that they may choose to shorten it for specific populations, based on their epidemiological context.
Thank you.