On somewhat further investigation (really limited here—lets not lean too much on it) -- the Moderna boosters are half the dose of the Moderna primaries. If you believe, as I do, that the primary reason for increased Moderna efficacy in trials was due to dosing, then the reduced booster dose means that the reason I give above (higher efficacy) is no longer a relevant factor.
I do think @npostavs is right that this study is likely quite confounded. Though I do still believe Moderna primary doses had reasonably better efficacy against OG covid, and in all likelihood against delta and now omicron.
On somewhat further investigation (really limited here—lets not lean too much on it) -- the Moderna boosters are half the dose of the Moderna primaries. If you believe, as I do, that the primary reason for increased Moderna efficacy in trials was due to dosing, then the reduced booster dose means that the reason I give above (higher efficacy) is no longer a relevant factor.
I do think @npostavs is right that this study is likely quite confounded. Though I do still believe Moderna primary doses had reasonably better efficacy against OG covid, and in all likelihood against delta and now omicron.