Moderna is also saying about the variants that their vaccines produce soup of antibodies rather than against any specific variant if I understood correctly. If true, we are in a good shape against many variants. mRNA technique seems extraordinary.
I for one would not be happy if this was developed anytime soon. I have gotten a flu shot every year since I can remember. I will continue to do so, however, I do NOT want and have no intentions of getting a covid booster any time soon. If combined is the only option then my choice would probably be no flu shot. I could change my mind in the future but not now.
Moderna or mRNA vaccines are not unique in that the ancestral spike protein is still similar enough to the B.1.617.2 / Delta variant spike protein that antibodies induced by vaccination do bind to the B.1.617.2 / Delta variant spike protein (just at somewhat lower efficiency). Moderna had previously designed a vaccine specific to the B.1.351 / Beta variant and found that it induced antibodies with improved binding against that variant’s spike protein.
The B.1.617.2 / Delta variant may be causing more breakthrough (and non-breakthrough) infections because exposures may have larger doses of virus (since viral loads tend to be so much higher), in addition to somewhat lower efficiency of antibodies from vaccination or previous infection with other variants.
I think in the big picture, looking at community health in general, it makes more sense to get vaccines to the unvaccianted before giving people who are vaccinated a third shot. This will help the bigger goal of reducing spread, saving lives, and keeping people out of the hospital. It also gets us to herd immunity quicker.
From what I understand, Moderna is suggesting a half dose for the third shot. It produced strong protection in their clinical trial. It probably won’t hurt to wait a bit until they come up with a clear guideline on the booster.
One thing that bothered me (as a Moderna recipient) was that Moderna used over 3x the amount of vaccine as Pfizer, yet did not get superior results. So I am happy to hear Moderna’s booster has less vaccine. I’d still be willing to get Pfizer as a booster, though, because it has even less vaccine (at least knowing what we do now; if studies show that is not good, I will reconsider). How long will the Moderna folks have to wait for their booster, if one can’t mix brands, because Moderna is always a few steps behind Pfizer?
Just read that the statistics from Moderna (93% effective after 6 months) and Pfizer (84% effective after 6 months) were compiled before Delta. Delta has since taken over as the dominant form of COVID. (Boston Globe)
One commenter cited a 16% effectiveness for Pfizer against infection with continuing protection against serious illness, hospitalization and death. I cannot find that number.
The article mentions B and T cells, and the complexity of the immune system beyond the antibody stats. And that antibodies wane but are regenerated by exposure to the virus. I wish we could see a really good explanation of how the immune system works with these vaccines, but I suspect experts don’t really know.
Keep in mind that UK’s strategy was to give one dose first to everyone, then give second doses later, so most people in UK received that second dose later than most people in the USA. Hence they would be expected to have higher antibody titers at the time that Delta hit.
Not mixing brands of vaccines (for any vaccine, not just COVID-19) is specified within a series (e.g. for both doses of a two dose series), presumably because mix and match is not tested in trials.
But I have never heard of that being a problem with getting a later booster with any vaccine. For example, people do not have to specify brands when getting flu or Tdap boosters.
In the UK they mixed brands because of the AstraZeneca clotting issue. Women under 40 who received the first dose of AZ received a second dose of Pfizer.
I read that the government wants a unified approach when they come out with booster shot recommendations so as to not confuse the public, so maybe they will make it clear that it is okay to switch brands for the mRNA booster shots.