This is an emerging topic. Related questions have been asked tangentially, but up till now very little information was confirmed.
As the vaccination regime evolves, new data becomes available. This thread is suggested as a single collection point as more and better information evolves in the coming weeks and months.
The first salvo:
This will definitely become a subject of real interest in the near future, for two reasons. First, inconsistent availability in some areas will lead affected people to ask if there’s a down side or potential risk to following a first shot with a second of a different type. Second is the inverse: others, possibly with special requirements, will ask whether mixing types confers additional benefits.
My wife is in the second group. She got AZ #1 weeks ago, just before it was contraindicated for her age cohort. Now she’s stuck in the debate over whether to continue or switch gears. (This is specific to our region and is non controversial in other areas.) She also expects to return to business travel in the next year and will be exposed to multiple variants.
At this point the evidence is insufficient to draw any conclusions or make any plans. But we’re watching closely.
(I got Moderna #1 a while back and will be getting #2 shortly so this is a less pressing practical concern for me.)
I don’t find the cite, but I listened on line to a public hearing of the European Parliament about 6 weeks ago where the parliamentarians asked scientists this precise question. The answer back then was (quoting from memory): “The vaccines were not designed to be mixed, nor were the trials on efficiency or safety and security. But as problems with availability and acceptance emerge, we keep a close eye on the results and hope to learn from the data. Right now we do not recomend mix and match. We hope to learn more shortly.”
This article might interest you too:
I find it strange how things suddenly pop up when you just read soomething related. Just came across The Lancet:
and El País (Spanish, for translations I recommend using deepl.com):
The Spanish data are mentioned in passing in the survey article I linked in the OP. That’s why I started the thread, actually — after months of “we don’t know yet but studies are in progress,” as you noted, there’s now some legitimate information to report.
Of course, the mainstream media is breathlessly oversimplifying the preliminary conclusions (“two types of vaccine are better than one!”), but that’s par for the media course.
There’s two sorts of answer to this question: What’s most likely to be true, and what we should assume is true for purposes of designing policies. Mixing vaccines probably does work, since they’re all based on increasing immune response to the same virus, and in fact (so far as I know) to the same protein on that virus. But until we’ve studied it, we can’t be sure, and so policies shouldn’t be based on that assumption.
Of course. As I note in the OP, this is a subject where definitive information is lacking, but will be evolving over the coming weeks and months. But it’s also a topic of interest, so I started a thread to collect those reports as they begin to emerge.
Following with interest.
I received my 1st AZ shot 5 weeks ago. AZ has been paused for 1st doses here, although they are just starting 2nd shots for people who received it about 10 weeks ago. There is talk about optionally giving an mRNA second dose here, but we are waiting on the studies.
Who arranges and pays for studies like this generally? Do Pfizer and Moderna team up for one study, Pfizer and AstraZeneca team up for second, etc.? Or are they run at the government level?
Just bumping the thread to ask for updates—it’s been almost three months, and I haven’t seen any further evidence. Is there any, or is it too soon?
heterologous vaccination more effective than homologous vaccination in immune-suppressed patients:
How Covid-19 vaccinations activate the immune response in organ transplant recipients (idw-online.de)
I’ve reat that Germany (STIKO) is recommending heterologous vaccination Research results on mix-and-match vaccinations published (medicalxpress.com), but I don’t have any direct knowledge.