One of the curious things I spotted in the info I posted above about the Shingrix is that the Phase 3 test appears to have had 29,200 participants, half receiving the vaccine, half a placebo. IIRC, the Pfizer vaccine Phase 3 test has ~60,000 participants (IIRC it was 30K initially, but at Pfizer's request the number was bumped up to 60K). And IIRC, 30,000 are participating in Moderna's and J&J's Phase 3 tests. I used present tense because I'm pretty sure the participants who received the vaccines are still being tracked.