[jyl]

So far, I haven’t seen any data suggesting that “mixing” vaccines A and B gives a better result than the more effective of A or B alone. Other than logistical advantages. But more data will come.

The bigger issue is going to be virus variants i.e. mutations. Unfortunately, so many people in the US will refuse to be vaccinated, even after vaccine supply is ample, that there will be a large pool of unvaccinated people for the virus to circulate and evolve in And so many countries will not have access to vaccine this year and next year, that there will be an even larger global pool out there. So this virus will not be suppressed like we (humankind) were able to suppress polio, measles, etc.

It isn’t so much a problem of vaccine efficacy, in my view. The current vaccines range from very to fairly effective against the main variants (and from very to extremely effective against severe disease caused by those variants), and if 80-90% of the population were vaccinated with the better vaccines we could probably suppress Covid regardless of its mutation - Israel is the test case here. The problem is that few countries will achieve more than 60-70% vaccination rate, and many will find that they have used the least effective vaccines - Chile is learning that now, with the Sinopharm vaccine.

The good thing is that some of the vaccines can be relatively quickly modified to address new variants. That would seem to me like the main reason to get vaccine A now and vaccine B later. Ultimately my guess is that Covid vaccination will be a routine annual thing, like the flu vaccine is, and each year you might get a mix (non-technical term) formulated to address the main variants of concern that year. If you’re in the US or similar rich country, that is.

The US and other rich countries really need to spend whatever it takes to get the rest of the world vaccinated ASAP. Letting the virus burn hot anywhere in the world is a threat to everywhere else.