how strict is the cut off point for an AZ vaccine?

[willbo]

I had my first dose of AZ vaccine a day over 13 weeks ago. A lot of stuff has happened to me in the meantime and I lost track of time. I told my family and they went hysterical and said I need to "start again" as I missed the time.

I thought they would contact me and give me a date, then a lot of busy stuff happened to me in the past 3 weeks and I totally forgot to chase it up.

I tried to make an appointment online and they gave me 8 july, which would be over 15 weeks since my first dose.

I'm going to the vaccine centre tommorow morning to try to ask for a walk in. How strict is the 12 week cut off? Am i wasting my time?

[steveh]

12 weeks between doses is the optimum for AstraZeneca and from what I've read 4 weeks either side is unlikely to matter much but talk to the doctor when you go for the jab who will be able to give you proper advice.

[Ferris]

Until this week, the suggested gap for AZ was mandated at 105 days (or 15 weeks) in Canada. You'll be fine - check with a doc there if helpful but I doubt it makes any real difference.

[willbo]

Until this week, the suggested gap for AZ was mandated at 105 days (or 15 weeks) in Canada. You'll be fine - check with a doc there if helpful but I doubt it makes any real difference.

thanks, that's set my mind at rest a bit, appreciate it

I think I read Ireland was doing longer gaps too, as well as a lot of Asia

[Ferris]

It's a balance between supply and efficacy everywhere depending on logistics and everything else.

We're importing every vaccine because our production facilities were shut down (thanks, Harper!) so at the beginning of all this, the Canadian NICE equivalent was suggesting 4+ months between doses. That went down to 15 weeks beginning of the year and has only been bumped up because our supply quadrupled in the last week and everyone has to pretend the best schedule is whatever manufacturers send us.

[aunt mildred]

Was thinking about this too. I'm going for my second AZ today, 13 weeks after the first. I couldn't get the second one sooner as it was fully booked. I had no side effects last time and hoping for the same this time.

[willbo]

Was thinking about this too. I'm going for my second AZ today, 13 weeks after the first. I couldn't get the second one sooner as it was fully booked. I had no side effects last time and hoping for the same this time.

I just had a walk in 2nd dose today, 13 weeks and 2 days after my first. The doctor told me it would be less effective than if I had it sooner but not to worry and it was still worth having. I felt really rough and flu like after the first but feel fine so far.

[greencalx]

The reason that people talk about 4 weeks and 12 weeks is that (as far as I could ascertain from googling) all the available data relates to those dosing intervals. The longer of the two gives you better protection. One assumes that the protection increases continuously from 4 to 12 weeks. Whether 12 is optimal is unclear without any further information (which may exist, I've just not seen it). It's worth noting that the spread in efficacy between individuals at any given time point is fairly wide (±5 percentage points or thereabouts, if I recall) which is commensurate with varying the interval by a couple of weeks. I guess this is why missing 12 weeks by a couple of weeks is unlikely to be a biggie. I don't understand how the immune system works, or what the typical profile looks like for other vaccines, but it would be surprising if the efficacy immediately fell off a cliff from exactly 12 weeks; even more surprising for a second jab at say 15 or 16 weeks to be worse than not having one at all.

I'm willing to be surprised if someone does manage to find the data, but I've not been able to turn anything up other than the 4 and 12 week trials yet.

[steveh]

If I understand it correctly, the length of time between doses is primarily determined by how long it takes the body to clear the vaccine so the immune system can then be stimulated again by a second dose. The Pfizer and Moderna ones are cleared within around a month but the AstraZeneca one persists for several months continuing to stimulate the immune system. This turned out to be longer than they thought but as you say I don't think there's anything published yet on what the true optimum is rather than the optimum from what's known right now.

[aunt mildred]

Had it a few hours ago, nothing's  fell off yet. I think I got a butcher this time as it hurt when I was jabbed and it started bleeding so got a cotton swab taped to my arm, I didn't even feel it first time. Arm is twanging a bit but not too bad yet. In and out in about ten minutes both times, very efficient.

[willbo]

I was in agony after my first - sore arm/ flu aches, but I feel nothing now, not even a sore arm. Feel like they just put water in as a placebo

[Harry Badger]

I've got a slightly different issue - I wasn't due my second one til about the 20th July but just had a letter asking me to come in on 29th June, so just under ten weeks. Obviously they are pushing ahead here in Wales.

[mjwilson]

Yeah I had an email saying I could cancel my existing second jab and boom a new one earlier, so looks like they are trying to speed things up a bit.

[paruses]

I've got a slightly different issue - I wasn't due my second one til about the 20th July but just had a letter asking me to come in on 29th June, so just under ten weeks. Obviously they are pushing ahead here in Wales.

Also in Wales and reading this have realised my 2nd jab on 2nd July will be only 8 weeks after the first.

Read in the Post this morning that WG are pushing to get 20k people double vaccinated as soon as possible (can't remember why).

[machotrouts]

You'll be fine. I got my first jab 16 weeks ago and still haven't had my second jab because I missed the appointment and decided not to reschedule because I've gone fucking mental and decided to withdraw from society. And I'm fine! ♥️

[greencalx]

Paper out today suggesting (as I had suspected, albeit without expert knowledge or any evidence) that a longer gap tends to elicit a stronger response after the second dose: https://papers.ssrn.com/sol3/papers.cfm?abstract_id=3873839. Main findings seem to be that raised antibody levels remain one year after a single dose, and that a 2nd dose at 45 weeks gives a higher response than at 12 weeks. Not sure how antibody response translates to efficacy though, and of course there is a trade-off between having a bit more protection now vs lots more protection later (when it might be too late). In any case, a third dose seems to improve things further, so I really don't think it's critical - probably you can just keep taking more doses until we've got things under control.

[steveh]

Also a report of a paper yesterday that if you've had Pfizer or Moderna then you probably won't need a booster for a while yet.

This is a good thread on this area: https://twitter.com/DavidLVBauer/status/1409640451326439432. Mentions there is a UK study on identifying the characteristics of those who may have insufficient protection.

[greencalx]

Based on this my guess is that the strategy will be something like getting everyone double vaxed with whatever's lying around in the first instance, then following up those who've been AZ'd with an mRNA jab when the need for urgency has subsided. Not a ridiculous strategy but does rely on being able to splash the cash, which not every country will be able to.