Earlier quoted context omitted.
They were found to inhibit infection via PCR testing and comparison with a control group. There may be a waning effect, especially with delta. I don't believe they're perfect by any means, but they certainly aren't worthless.
That is absolutely not something the found in the clinical trials.
...
"Among 42,094 evaluable ≥12-year-olds without evidence of prior SARS-CoV-2 infection, 77 COVID-19 cases with onset ≥7 days post-dose 2 were observed through the data cut-off (March 13, 2021) among vaccine recipients and 850 among placebo recipients, corresponding to 91.3% VE (95% CI [89.0-93.2]; Table 2). Among 44,486 evaluable participants, irrespective of prior SARS-CoV-2 infection, 81 COVID-19 cases were observed among vaccine and 873 among placebo recipients, corresponding to 91.1% VE (95% CI [88.8-93.0]).
In the all-available population with evidence of prior SARS-CoV-2 infection based on positive baseline N-binding antibody test, 2 COVID-19 cases were observed post-dose 1 among vaccine and 7 among placebo recipients. In participants with evidence of SARS-CoV-2 infection by positive nucleic acid amplification test at baseline, no difference in COVID-19 cases was observed between vaccine (n=10) and placebo (n=9) recipients (Table S5). COVID-19 was less frequent among placebo recipients with positive N-binding antibodies at study entry (7/542; ~1.3% attack rate) than among those without evidence of infection at study entry (1015/21,521; ~4.7% attack rate), indicating ~72.6% protection by previous infection."
...
Efficacy peaked at 96.2% during the interval from 7 days to https://www.medrxiv.org/content/10.1101/2021.07.28.21261159v...