Nä, just det är ju faktisk med i det jag citerade från studien - jag tror att du råkade hoppa över just detta faktum i din kommentar
Padirac skrev 2021-09-05 19:02:52 följande:
Det verkar som att åldersspannet för maskbärarna avgör om det finns någon statistiskt säkerställd effekt av mask och social distansering.
Studien undersöker effekten av maskbärande (cloth och surgical) och social distansering.
Preprint finns här -
www.poverty-action.org/sites/default/files/pu...
"3.2 Outcomes Our primary outcome was symptomatic seroprevalence for SARS-CoV-2. Our secondary outcomes were prevalence of proper mask-wearing, physical distancing, and symptoms consistent with COVID-19. For COVID-19 symptoms, we used the symptoms that correspond to the WHO case definition of probable COVID-19 given epidemiological risk factors: (a) fever and cough; (b) three or more of the following symptoms (fever, cough, general weakness/fatigue, headache, 2The need for continued monitoring and retraining is a core part of our scalable intervention protocol, available here (in the online version of this article). 8 myalgia, sore throat, coryza, dyspnea, anorexia/nausea/vomiting, diarrhea, altered mental status); or (c) loss of taste or smell. Seropositivity was defined by having detectable IgG antibodies against SARS-CoV-2."
"Mask-wearing and physical distancing were assessed through direct observation at least weekly at mosques, markets, the main entrance roads to villages, and tea stalls. At 5 and 9 weeks follow-up, we surveyed all reachable participants about COVID-related symptoms. Blood samples collected at 10-12 weeks of follow-up for symptomatic individuals were analyzed for SARS-CoV-2 IgG antibodies. Results: There were 178,288 individuals in the intervention group and 163,838 individuals in the control group. The intervention increased proper mask-wearing from 13.3% in control villages (N=806,547 observations) to 42.3% in treatment villages (N=797,715 observations) (adjusted percentage point difference = 0.29 [0.27, 0.31]). This tripling of mask usage was sustained during the intervention period and two weeks after. Physical distancing increased from 24.1% in control villages to 29.2% in treatment villages (adjusted percentage point difference = 0.05 [0.04, 0.06]). After 5 months, the impact of the intervention faded, but mask-wearing remained 10 percentage points higher in the intervention group."
"Because the study was powered to detect differences in symptomatic seroprevalence, we cannot distinguish whether masks work by making symptoms less severe (through a reduced viral load at transmission) or by reducing new infections. We selected the WHO case definition of COVID-19 for its sensitivity, though its limited specificity may imply that the impact of masks on symptoms comes partly from non-SARS-CoV-2 respiratory infections. If masks reduce COVID-19 by reducing symptoms (for a given number of infections), they could help ease the morbidity and mortality resulting from a given number of SARS-CoV-2 infections. If masks reduce infections, they may reduce the total number of infections over the long-term by buying more time to increase the fraction of the population vaccinated. At the time of the study, the predominant circulating 33 SARS-CoV-2 strain was B.1.1.7 (alpha)[62]. The impacts of the delta variant on the number of infections prevented by a given mask-wearer are uncertain; the population-wide consequences of infections prevented by a given mask-wearer may be larger given a higher reproduction number.
We estimate that a scaled version of our intervention being implemented in Bangladesh will cost between $10K and $52K per life saved, depending on what fraction of excess deaths are attributable to COVID-19. This is considerably lower than the value of a statistical life in Bangladesh ($205,000, [63]) and under severe outbreaks, is comparable to the most cost-efficient humanitarian programs at scale (e.g. distributing insecticide nets to prevent malaria costs $9,200 per life saved [64]). This estimate includes only mortality impacts but not morbidity, and greater cost-efficiency is possible if our intervention can be streamlined to further isolate the essential components. The vast majority of our costs were the personnel costs for mask-promoters: if we consider only the costs of mask production, these numbers would be 20x lower. Thus, the overall cost to save a life in countries where mask-mandates can be enforced at minimal cost with existing infrastructure may be substantially lower than our estimates above."
"Physical Distancing Contrary to concerns that mask-wearing would promote risk compensation, we did not find evidence that our intervention decreases distancing behavior. In the second panel of Table A4, we report identical specifications to the first panel, but with physical distancing as the dependent variable. In control villages 24.1% of observed individuals practiced physical distancing compared to 29.2% in intervention villages, an increase of 5.1% (a regression adjusted estimate of 0.05 [95% CI: 0.04,0.06]) Evidently, protective behaviors like mask-wearing and physicaldistancing are complements rather than substitutes: endorsing mask-wearing and informing people about its importance encouraged rural Bangladeshis to take the pandemic more seriously and engage in another form of self-protection. The increases in physical distancing were similar in cloth and surgical mask villages."
In summary, we found that mask distribution, role modeling, and promotion in a LMIC setting increased mask-wearing and physical distancing, leading to lower illness, particularly in older adults. We find stronger support for the use of surgical masks than cloth masks to prevent COVID19. Whether people with respiratory symptoms should generally wear masks to prevent respiratory virus transmission?including for viruses other than SARS-CoV-2?is an important area for future research. Our findings suggest that such a policy may benefit public health."
