“…Thus this desperate headlong rush in Israel to give third doses.
And they are using Moderna for third doses not Pfizer and I suspect they believe Moderna is more effective than Pfizer but not publicly saying it.”
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I think your suspicion may be on the money. BeauBo’s (August 11th) daily SITREP provided a link to a Mayo Clinic Study which compared the relative effectiveness of the Moderna (mRNA-1273) vaccine and the Pfizer (BNT162b2) vaccine at preventing detectable infection by the virus that causes COVID-19. While both vaccines were highly effective at preventing infection (compared to the “control” group of unvaccinated individuals also in the study) in the study there was a difference in their RELATIVE ability to prevent DETECTABLE breakthrough infection. As BeauBo said, the study’s peer review is in progress. Below is a hot link to the write up for the study followed by a one sentence extract:
https://www.medrxiv.org/content/10.1101/2021.08.06.21261707v1.full.pdf
“…In Florida, which is currently experiencing its largest COVID-19 surge to date, the risk of infection in July after full vaccination with mRNA-1273 was about 60% lower than after full vaccination with BNT162b2….”
Several countries are adopting mix&match approaches with vaccines, rather than strictly keeping the same type for subsequent shots.
Some studies have shown improved effectiveness, and it makes intuitive sense, if the body is trained to recognize more different features (epitopes) of the virus, that the different vaccines use.
As House Atreides mentioned elsewhere, Moderna may have just gotten lucky that their mix of features happens to better target Delta’s. Even if it doesn’t do so markedly, just mixing the vaccine types may improve results, with a wider variety of viral markers targeted.
Once full FDA approval is given to Pfizer and Moderna (looks like next month), they can use expedited procedures (like the annual flu shot), to tweak their mix for current variants.