The CDC suggsts that the optimum window for Pfizer is apparently 17-25 days (usually 21 is set as the minimum) and 24-32 days for Moderna (usually set at 28 days). They say up to 42 days for either seems perfectly fine. I had my first Pfizer shot not quite two weeks ago and am not scheduled for my second for another couple of weeks - 28 days like a Moderna schedule. I assume because they were scheduling both appointments at the same time and didn’t know which I’d get ahead of time.
However for Astra-Zeneca it is much longer - the optimum apparently is around twelve weeks. So if she got AZ, that looks about right.
Ah, poking around further this is apparently a slightly controversial decision the Canadian government made (following in the footsteps of the UK) to get as many vaccinated as possible as quickly as possible given scarce supply. So they delay up to four months.
Probably fine and under the circumstances maybe even wise. But a little bit of an unknown.
Here in Saskatchewan, I’m 68, wife 66 and we’re both booked for April 15. A friend in Regina who is 62 did the “wait in line for 4 hours” 1st come/first serve drive through and got vaccinated last week.
Canada suspends AstraZeneca vaccine for everyone under 55:
Questioned about the general safety of AZ, an immunology specialist interviewed on the radio today said he had no concerns about it, and would not hesitate recommending it to his own parents.
Due to no appropriately powered COVID vaccine study having been done comparing different intervals, the decision on spacing can only be based on low quality data. How the Phase 3 was done is one factor. What’s worked best with other vaccines is another (longer, I think).
I think medical historians might reasonably have some input.
On the plus side, the range of intervals that work is likely wide
I just booked my Pfizer or Moderna vaccine here in Ontario. I was happy to get the booking (first shot in about three weeks) but I was astounded to see that the booster is not until August!
It appears that, based on the recommendations of the National Advisory Committee on Immunization, Ontario has extended the interval to four months, mainly in order to maximize the number of people getting at least the first shot as soon as possible. More details in the article below. What bothers me is that this directly contradicts the advice of the CDC, which is still sticking to recommending a minimum of 21 days for the Pfizer vaccine (29 for Moderna) with a maximum of 6 weeks, claiming inadequate evidence of efficacy beyond that time. Either the CDC is sticking to outdated data, or Canada’s NACI is making recommendations based on a paucity of clinical evidence.
UK did this and is looking pretty smart for having done so at the moment, frankly. Their vaccination rates are high (for at least one dose) and their infection rate is lower than US, Canada, and the rest of Europe and falling.
CDC is sticking with the conservative approach, which is what I tend to follow in my clinical thinking, but I acknowledge there are times to consider alternate approaches when the stakes are high.
Thanks for the input. I confess I did a double-take when I took a closer look at my appointments and saw how far apart they were, and then had a hell of a time finding an actual human who could explain it, until I found that news article. I agree it makes sense, and I’m sure that the Advisory Committee has a lot more data than I have about efficacy after four months (it’s actually closer to 3 1/2). I’m just happy to be getting either the Pfizer or Moderna vaccine due to the continuing controversy over AstraZeneca, whether justified or not.
My wife was picking up something from the pharmacy on Saturday and the tech told her that we can sign up for the waitlist- so she signed us both up. We’re supposed to get contacted in the next week or so for the Moderna shot.
I fully expect to have to have covid shots yearly for the foreseeable future. An extended delay now, but expanding coverage to drop cases, seems like a reasonable choice IF you’ll be getting a covid shot again when covid season rolls around.
Mrs Piper got her first shot yesterday. We’ve both got first shots now.
Drive-through, no appointment clinic in Regina is working well and picking up speed. When I went I waited for several hours in line, but she was in and out in less than half an hour. The single longest wait for her was the 15 minute post-jab period to make sure no adverse reaction.
There’s also the factor that even one shot reduces the severity of COVID if you do get it, and also apparently reduces how contagious you are.
My sister got her first vaccine back in February, and then tested positive for COVID just a few weeks ago. But she didn’t develop any symptoms, and her husband never tested positive.
So, yeah, it’s a complicated situation, but the strategy of getting more people the first dose does have some merits. The US can afford to be more conservative, because they’ve ramped up their domestic production to such a level that they don’t really need to play this game of balancing priorities.
Here’s a good CTV article with info on comparative rates for vaccination across the country, including the rate of usage of doses delivered to each province/territory.
It’s interesting that for all the flack in the press about the delays in vaccination, the only two G20 countries are ahead of us are the UK and US. Even Germany, the home of BioNTech is not doing as well as Canada.
Germany (and some other EU countries) have administered more doses per capita than we have. We have more people (per capita) with at least one dose. That’s down to the decision to prioritize first doses rather than following the drug companies’ recommended dose schedule.
Still, we’re only just barely behind most of the EU countries in total doses. I’m optimistic that the gamble of delaying second doses will pay off. We have so much excess vaccine on order we can easily give everyone a third booster shot in fall sometime if it should become necessary, and in the mean time it seems much more valuable to use the next available dose to move someone from 0% to 80% resistance rather than to move someone from 80% to 90% resistance.
Yup. Noticed at lunchtime they’d dropped eligibility from 52 to 51, and promptly headed over. Only an hour wait. Glad I went, because it was apparently 4+ hours today after they dropped eligibility to 48.
