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...”the conclusions are at odds with those from smaller studies published by Johnson & Johnson earlier this month suggesting that a single dose of the vaccine is effective against the variant even eight months after inoculation.

“The new study has not yet been peer reviewed nor published in a scientific journal, and relied on laboratory experiments...

“...Small studies published by researchers affiliated with J&J suggested that the vaccine was only slightly less effective against the delta variant than against the original virus, and that antibodies stimulated by the vaccine grew in strength over eight months.

“Landau’s team would probably have seen a similar increase in the vaccine’s potency if they had looked at the data over time, said Dan Barouch, a virologist at Beth Israel Deaconess Medical Center in Boston. The data on the J&J vaccine’s strength against the delta variant at Day 29 is not much different from those reported in his own study, Barouch said.

https://www.baltimoresun.com/coronavirus/ct-aud-nw-nyt-johnson-and-johnson-vaccine-delta-variant-20210720-firar53ytzdc7hewcdvqhm7jdm-story.html

https://www.jnj.com/positive-new-data-for-johnson-johnson-single-shot-covid-19-vaccine-on-activity-against-delta-variant-and-long-lasting-durability-of-response

Safety and Efficacy of Single-Dose Ad26.COV2.S Vaccine against Covid-19

“...Vaccine efficacy was higher against severe–critical Covid-19 (76.7% [adjusted 95% CI, 54.6 to 89.1] for onset at ≥14 days and 85.4% [adjusted 95% CI, 54.2 to 96.9] for onset at ≥28 days).”
https://www.nejm.org/doi/full/10.1056/NEJMoa2101544

“...The J&J/Janssen COVID-19 Vaccine was 66.3% effective in clinical trials (efficacy) at preventing laboratory-confirmed COVID-19 infection in people who received the vaccine and had no evidence of being previously infected. People had the most protection 2 weeks after getting vaccinated.
In the clinical trials, the vaccine had high efficacy at preventing hospitalization and death in people who did get sick. No one who got COVID-19 at least 4 weeks after receiving the J&J/Janssen COVID-19 Vaccine had to be hospitalized....”
https://www.cdc.gov/coronavirus/2019-ncov/vaccines/different-vaccines/janssen.html