There is now fairly good evidence that the AZ vaccine is worse in the short term but offers a small level of longer term protection (compared with Pfizer) due to it offering a tiny amount of cellular immunity, whereas the Pfizer vaccine appears to offer none. This is tiny in comparison with natural infection, but it is nevertheless there.
We can also now see that the rate of clot-related problems from AZ is similar to that seen with Pfizer (rare but not at levels that can be ignored in risk/benefit calculations). There are far more clot-related problems for AZ registered with the Yellow Card system, but that appears mainly to be associated with enthusiasm, not reality.
Thus it would appear that the policy change last spring to not give AZ to younger folk was based on flawed science and might have made things worse.
And the reason we might have made things worse is because we didn't do robust pharmacolvigilance when the vaccines were rolled out, but instead hoped for the best. You'd think that the recent data would have resulted in robust pharmacovigilance being used for the vaccine rollout to children and for the third booster, but no -- even with current evidence showing how useless their Yellow Card system was and how it has led to policy mistakes being made, they're still not doing robust pharmacovigilance, and are still hoping for the best.
But, then again, perhaps robust pharmacovigilance would highlight an increased risk of hospitalisation/death in the vaccinated due to vaccination, due to their immune system being suppressed, or due to ADE -- and we can't have that.
@amanuensis No there isn't.
Every study on waning so far (measuring actual infections) as shown that although Pfizer wanes more rapidly, at no point does it ever get lower than AZ was at its very best.
Zoe data from this weeks presentation shows AZ protection against serious illness wanes significantly MORE then Pfizer. 6 months down the line hospitalisation is down to 75% whereas Pfizer remains at 83% or so.
There isnt a single study, for any time period, where AZ protection against serious illness OR infection is ever equal to or above Pfizer.
AZs main problem is and always has been its lack of efficacy as opposed to safety.
I was referring to direction of travel, rather than where we are now. Models suggest that there will be a crossover point over the next few months where the relative performance of AZ vs Pfizer swap over.
PHE published this today on vaccine efficacy.
Shows AZ is significantly worse than Pfizer:
After 20 weeks vs Delta, AZ shows 47% efficacy against symptomatic disease and 77% hospitalisation.
Pfizer in the same period shows 70% against symptomatic infection and 93% against hospitalisation.
That's a big big difference, can easily account for increased UK deaths and keeping cases higher.
I'm guessing unofficial policy is to get everyone that had AZ an mRNA booster.
@splattt the booster will be pfizer, as you guessed
it seems to last longer than az.
Interesting study. Does seem to show the justification for booster jabs, for the vulnerable.
Indeed, it seems that policy will be mRNA booster jabs.
The disclosure of limitations section is interesting, in that it shows some of the complexities of a real life study. For instance the unvaccinated control isn't necessarily without protection, since some will have been infected but not received a positive test to be excluded.
They admit that the effect of who got which vaccine probably isn't fully mitigated by their age stratification. I'd say that that is certainly true, as age bands 24 years wide are used, will certainly hide age factors. Probably the case that narrower bands would have resulted in very wide confidence intervals. Even within the wide bands there are some examples of this.
Interesting to see the comment on Israel's issues with breakthrough infections, possibly explained by the shorter time between doses.
Interesting study. Does seem to show the justification for booster jabs, for the vulnerable.
Indeed, it seems that policy will be mRNA booster jabs.
The disclosure of limitations section is interesting, in that it shows some of the complexities of a real life study. For instance the unvaccinated control isn't necessarily without protection, since some will have been infected but not received a positive test to be excluded.
They admit that the effect of who got which vaccine probably isn't fully mitigated by their age stratification. I'd say that that is certainly true, as age bands 24 years wide are used, will certainly hide age factors. Probably the case that narrower bands would have resulted in very wide confidence intervals. Even within the wide bands there are some examples of this.
Interesting to see the comment on Israel's issues with breakthrough infections, possibly explained by the shorter time between doses.
Lots of these VE studies have issues in that they dont screen for (or test for) prior infection.
This does mean VE will be lower in several of them as a result.
Made worse by the fact the UK is one of the few countries that for inexplicable reasons refuses to recognise prior infection as protection
AZ is highly effective and very cheap. A wonderful tool is the battle against the virus.
@thinksaboutit Its a 2nd tier jab that will be used globally because its cheap.
Ultimately it stops a lot fewer people dying than mRNAs but for places that cant get anything else, its better than nothing.
Small reduction in efficacy vs. massively raised potential to vaccinate (cost,handling) is a winning combination.
And it is a LOT better than nothing, as you well know.
Handling isnt an issue and hasnt been since the first few weeks. Anywhere that can handle meat can handle Pfizer.
And Moderna is even easier.
The efficacy reduction is massive. Its in the region of 30-40% for infection and serious illness.
Its better than nothing but not by a lot. Any country relying on it alone will be in huge trouble with a massive death toll and overloaded health systems.
There is some confusion with your views on this topic....
Looking back at your prior post (in this thread) on the efficacy, you say....
"After 20 weeks vs Delta, AZ shows 47% efficacy against symptomatic disease and 77% hospitalisation.
Pfizer in the same period shows 70% against symptomatic infection and 93% against hospitalisation."
Using your own words 77% efficacy against hospitalisation. Now 77% is quite a substantial advantage over nothing. Don't you agree?
Why make sweeping statements that you have already shown to be untrue?
All my statements are true - i assume you haven't checked THIS weeks PHE release nor Israeli or Qatar data for various VEs?
AZ has dropped to effectively 0% (within the CIs) of efficacy after infection for 6 months plus and hospital below 50%.
The longer this goes on the more rapidly its dropping.
Although Pfizer is waning a lot, AZ is doing so at twice the rate. A key difference is Pfizer serious illness VE is holding up, AZs is not.
Every single study coming out shows AZ to be more and more worthless. Ultimately anyone getting it in any country is going to need an mRNA booster to make it useful.
PHE report Week 38 published 23 September says:
"After 2 doses, observed vaccine
effectiveness against symptomatic disease with the Delta variant reaches approximately
65 to 70% with AstraZeneca Vaxzevria and 80 to 95% with Pfizer-BioNTech Comirnaty
and Moderna Spikevax (3, 4) Vaccine effectiveness is generally slightly higher in
younger compared to older age groups. With both Vaxzevria and and Comirnaty, there
is evidence of waning of protection over time, most notably among older adults. There is
not yet enough follow-up with Spikevax to assess waning (3)."
No discussion of CI's.
Where did you find reference to CI's allowing you to derive your zero number?
