J&J says 2 doses 100% effective against severe Covid

Johnson & Johnson says additional dose boosts Covid vaccine efficacy
[See also J&J press release.] Johnson & Johnson said Tuesday that a large, global study showed its Covid-19 vaccine is more effective when given as a two-dose regimen, and that other data indicate the efficacy of the vaccine does not wane. The two-dose regimen prevented 75% of moderate to severe Covid cases in all countries where it was tested — and 94% of such cases in the United States, where fewer troublesome variants of the SARS-CoV-2 virus circulated at the time the trial was underway. Importantly, the two-dose regimen was 100% effective against severe disease. It appears J&J may use the data to argue in favor of making a booster broadly available to people who received the one-dose vaccine six months ago or more.

Effectiveness of the Single-Dose Ad26.COV2.S COVID Vaccine
[Johnson & Johnson.] Among 390,517 vaccinated and 1,524,153 matched unvaccinated individuals, VE was 79% (95% CI, 77% to 80%) for COVID-19 and 81% (79% to 84%) for COVID-19-related hospitalizations. VE was stable over calendar time. Among states with high Delta variant incidence, VE during June/July 2021 was 78% (73% to 82%) for infections and 85% (73% to 91%) for hospitalizations. These non-randomized data across U.S. clinical practices show high and stable vaccine effectiveness of Ad26.COV2.S over time before the Delta variant emerged to when the Delta variant was dominant.

Digital contact-tracing in France: uptake by COVID-19 risk factor and by exposure risk
Using a cross-sectional survey conducted in France in November 2020 (N = 1042), we investigate the factors associated with the use of the French ‘TousAntiCovid’ contact-tracing application. A negative association is found between the propensity to believe in COVID-19 conspiracy theories and the use of ‘TousAntiCovid’. French respondents at risk of severe COVID-19 form are more likely to use ‘TousAntiCovid’. No difference in uptake is found by exposure group. Governmental communication to fight COVID-19 misinformation and to stress out the utility and data safety of ‘TousAntiCovid’ should be reinforced.

Contact tracing is an imperfect tool for controlling COVID-19 transmission and relies on population adherence
Emerging evidence suggests that contact tracing has had limited success in the UK in reducing the R number across the COVID-19 pandemic. We investigate potential pitfalls and areas for improvement by extending an existing branching process contact tracing model, adding diagnostic testing and refining parameter estimates. Our results demonstrate that reporting and adherence are the most important predictors of programme impact but tracing coverage and speed plus diagnostic sensitivity also play an important role. We conclude that well-implemented contact tracing could bring small but potentially important benefits to controlling and preventing outbreaks, providing up to a 15% reduction in R.

Estimates of Cases and Hospitalizations Averted by COVID-19 Case Investigation and Contact Tracing in 14 Health Jurisdictions in the United States
The implementation of case investigation and contact tracing (CICT) for controlling COVID-19 has proven challenging. We used data on the proportion of cases interviewed, contacts notified or monitored, and days from testing to case and contact notification from 14 jurisdictions to model the impact of CICT on cumulative case counts and hospitalizations over a 60-day period. Performance by jurisdictions varied widely. Jurisdictions isolated between 12% and 86% of cases (including contacts that became cases) within 6 to 10 days after infection. We estimated that CICT-related reductions in transmission ranged from 0.4% to 32%. For every 100 remaining cases after other nonpharmaceutical interventions were implemented, CICT averted between 4 and 97 additional cases. Reducing time to case isolation by 1 day increased averted case estimates by up to 15 percentage points. We estimated that CICT reduced the number of COVID-19 cases and hospitalizations among all jurisdictions studied. Reducing time to isolation produced the greatest improvements in impact of CICT.