They found a tiny effect in self-reported non-blinded trial of adults only but it was not statistically significant. They did not measure whether participants had Covid, via a PCR test. The status of having PCR was simply self-reported by participants. Those in the mask control arm may have had a bias to report not having Covid. They also note that the non-masked group reported more public activities and events.
Results Between 10 February 2023 and 27 April 2023, 4647 participants were randomised of whom 4575 (2788 women (60.9%); mean age 51.0 (standard deviation 15.0) years) were included in the intention-to-treat analysis: 2313 (50.6%) in the intervention arm and 2262 (49.4%) in the control arm. 163 events (8.9%) of self-reported symptoms consistent with respiratory infection were reported in the intervention arm and 239 (12.2%) in the control arm. The marginal odds ratio was 0.71 (95% confidence interval (CI) 0.58 to 0.87; P=0.001) favouring the face mask intervention. The absolute risk difference was −3.2% (95% CI −5.2% to −1.3%; P<0.001). No statistically significant effect was found on self- reported (marginal odds ratio 1.07, 95% CI 0.58 to 1.98; P=0.82) or registered covid-19 infection (effect estimate and 95% CI not estimable owing to lack of events in the intervention arm).
Conclusion Wearing a surgical face mask in public spaces over 14 days reduces the risk of self-reported symptoms consistent with a respiratory infection, compared with not wearing a surgical face mask.
- 8.9% of those wearing a surgical mask got Covid over the 14-day period.
- 12.2% of those not wearing a surgical mask got Covid over the 14-day period.
Ignoring the lack of statistical significance, the self-reported Covid status, and the several confounding variables, wearing a surgical mask may delay getting Covid by a few days or weeks, per this study. We also need to ignore that the peak of the pandemic, globally (based on manufacturing data), the world was disposing/trashing 3 million used masks every minute: The world is consuming 3 million face masks PER MINUTE – Coldstreams
Since Covid always exists (in both people and animal populations), you will most likely eventually get Covid at least once. The CDC has estimated that most in the U.S. has had Covid at least once. Pandemics end through immunity, either from vaccination, having the disease, or both, or the virus mutates to a less invasive form.
Because the disease is always with us, a successful and effective NPI (if such exists), can only delay the onset of having the disease – unless you have a 100% effective NPI that is adhered to 100% of the time.
Update: Here is what a professor of medicine says about this study: A new mask randomized trial shows that masks work? (sensible-med.com)
Those who support masks say the above study confirms their effectiveness and we should wear them continuously, most of the year to avoid colds and influenza. They ignore that the study has sufficient problems that there is no certainty that the small risk reduction was due to the intervention.
