The Riverside data was from Feb-July, 2021. The SC data was from July 16-August 15 of 2021. So the SC data was totally apples to apples and included the delta variant. And importantly: The Riverside data was for Feb-July and ONLY 23 vaccinated people died during those 6 months. Out of nearly 2200 deaths!
Well Israel is a clue to what’s coming to the US. Data out of Israel and the UK is why the booster is being recommended here at five months after a previous vaccine.