Public health measures against COVID-19

The summary of the results cited in reference 68 of Xu et al. in Table 5 confuses me, because the paper does not contain the results. From the correspondence with the author, I think this is mislabeled and Reference 60 should be cited. If you can correct this error, or point it out in other ways, you may avoid the same confusion for others.

I do have some questions about the 2 studies used as input for meta-analysis.

Xu et al., Reference 60, doi: 10.2196/21372, is an analysis of self-report results through an online Internet survey conducted by WeChat. Recruit participants by seeding the survey to medical school students and faculty, as well as anyone the CDC and the research team can recruit. The author made it clear that this is not a random sample.

I may ask, what is the reason for assigning this risk of bias to Bundgaard et al.? Besides, can I ask why the Internet survey results of Xu et al. are more/more/weighted than Bundgaard's RCT?

Krishnamachari et al., doi: 10.1016/j.ajic.2021.02.002, reference 43, an observational study rated as "serious or critical" risk of bias. However, compared with an RCT by Bundgaard et al., this is also more weighted in the meta-analysis.

Krishnamachari is-like all observational studies of this scale, within such a wide geographic range (including the large differences in climate and factors that affect seasonal forcing)-must face serious risks of many confounding factors and therefore have biased ratings. Xu et al. As a completely non-systematic Internet questionnaire, there must be a greater risk of bias.

Therefore, it is strange that the weight of these studies is equal to or higher than the weight of RCT. Can the author give reasons to prove this?

I noticed that the result of the meta-analysis was 0.47 RR, which is much higher than the Bundgaard RCT result. However, Bundgaard RCT is designed to be able to clearly detect 50% of the impact, at the designed prevalence rate-prevalent during the study. Did not find any powerful effects.

For this meta-analysis, an impact of >50% was found to be inconsistent with the RCT evidence that should have clearly detected such a large impact but was not found, indicating that there is a problem. Especially when the 53% of the impact in this meta-analysis is so observational and non-random. A reasonable explanation is that these observational studies are very confusing and unreliable—and are over-valued.

Can the author explain this difference and why the weight of observational evidence (including the results of the Internet questionnaire) is so large, which leads to this difference?

In addition, the findings of Xu et al. and Krishnamachari et al. did not fit the format required for meta-analysis. I have collected a process from my correspondence with the author to convert the data back into the form required for meta-analysis. It is best to at least describe the process in detail in this article, or as an update attachment.

Conflict of interest: no conflict of interest

Thank you for collecting evidence and strengthening the information of public health officials throughout the pandemic. I hope readers will focus the discussion on the content at hand and read the full text because it may answer some of their questions.

Conflict of interest: no conflict of interest

Dear editor, good comments and comments. Shows that masks and hand hygiene are effective, while social distancing is ineffective. Oppose closing (social distancing), but support social separation (ie not hugging/shaking hands, etc.). Explain why air travel is safe. (People are disciplined)

I really don’t care about theory,...but this virus seems to be everywhere, including fecal-oral transmission and oral-hand-surface-hand-to-mouth transmission. Shouldn't masks work against aerosols that should pass directly through them? ...But you can stop touching your face in dangerous areas in public places by interrupting surface contact-hand-to-mouth transmission (after years of biting my nails, I now have a perfect cuticle!) If aerosols are important, social distancing should be Effective effective,...it is not.

SO For wards, it is mandatory to use FP3 masks. (Cambridge data) Yes. In other places (especially in densely populated places that may have been exposed), surgical masks and hand hygiene together seem to be essential to prevent waves?

Conflict of interest: no conflict of interest

The argument against wearing a mask is the same as that of a seat belt-not knowing how to wear it-will increase risk and so on. A double-blind study of parachutes failed to show the impact on fall risk.

Let us have a little common sense...

The particle size does not matter, because electrostatic factors must be considered. We are not talking about bullets, but about floating particles in suspension.

Conflict of interest: no conflict of interest

It is often unclear how the cited effect size was derived from the original study. For example, the study by Xu et al. (2020) The report stated that in the fully adjusted model, the odds ratio (OR) of not wearing a mask over wearing a mask is 7.20. This means that the approximate relative risk (RR) of wearing a mask is 1/7.2=0.139, or the efficiency of wearing a mask is 86.1%. However, this review cited an RR of 0.34 (Figure 5), and it is difficult to see how 0.34 was derived from Xu et al. (2020). Nevertheless, it shows that masks are more effective than certain vaccines with a ratio of 86.1%, which seems very suspicious.

Similarly, Krishnamachary et al. (2021) The report stated that “the adjusted ratio will be compared in 1 to 3 months with states that have implemented mask requirements in one month or less and did not produce statistically significant results (adjusted ratio = 1.20, 95 % CI: 0.91-1.61, P = .19). The rate of states that enforce masks within three to six months is 1.61 times that of states that implement masks within one month (adjusted rate = 1.61 (95% CI: 1.23- 2.10), P = .001). The rate of states that enforce or not enforce masks after six months is 2.16 times that of states that implement masks within one month (adjusted ratio = 2.16 (95% CI: 1.64-2.88, P) <.0001).” However, the unquoted RR (for delayed mask wearing) is compatible with the RR 0.77 cited for mask wearing in Figure 5.

Another question of Krishnamachari et al. (2021) Yes, states with early mask authorization also tend to implement other (usually stricter) non-pharmaceutical interventions (NPI) early. Therefore, it is difficult to know how much the mask contributes to the result. Although the authors classify the risk of bias in this study as "serious or critical," unfortunately, this study has the highest weight in the meta-analysis (Figure 5).

Although there is a lack of randomized controlled trials (only one eligible study has been identified), we have to rely on observational studies. However, although some observational studies seem to meet the inclusion criteria, they are still missing. Some examples of mask effects include: Dupraz et al. (2021); Fischer et al. (2021); and Mark et al. (2021). Fischer et al. (2021), similar to Krishnamachari et al. (2021), focusing on the state-level mask effect. Using multiple months of data, the mask task OR estimated in the fully adjusted model is not statistically significant. As for the adhesion of masks, the results have been mixed. Within two months, OR was statistically significant (July and September), but not the other two. Other research by Dupraz et al. (2021) and Marks et al. (2021) all reported statistically insignificant effects.

Overall, I totally agree with Linked Editor's view that the current quality of evidence (as reported in the paper) is "low or very low." Although the pandemic has been nearly two years old, the lack of high-quality research, especially randomized controlled trials on non-profit institutions, is disappointing. This may be one of the most important lessons of this pandemic.

References Dupraz, J., Butty, A., Duperrex, O., Estoppey, S., Faivre, V., Thabard, J., Zuppinger, C., Greub, G., Pantaleo, G., Pasquier, J ., Rousson, V., Egger, M., Steiner-Dubuis, A., Vassaux, S., Masserey, E., Bochud, M., Gonseth Nusslé, S., & D'Acremont, V. (2021) . The prevalence of SARS-CoV-2 among family members and other close contacts of COVID-19 cases: a serological study in Vaud, Switzerland. Public forum infectious diseases, 8(7). https://doi.org/10.1093/ofid/ofab149

Fischer, CB, Adrien, N., Silguero, JJ, Hopper, JJ, Chowdhury, AI, & Werler, MM (2021). Mask compliance and COVID-19 infection rates across the United States. Public Science Library One, 16(4), e0249891. https://doi.org/10.1371/journal.pone.0249891

Krishnamachari, B., Morris, A., Zastrow, D., Dsida, A., Harper, B. and Santella, AJ (2021). Before vaccination, the role of masks, stay-at-home orders, and school suspension in curbing the COVID-19 pandemic. American Journal of Infection Control, 49(8), 1036-1042. https://doi.org/10.1016/j.ajic.2021.02.002

Marks, M., Millat-Martinez, P., Ouchi, D., Roberts, C. h, Alemany, A., Corbacho-Monné, M., Ubals, M., Tobias, A., Tebé, C., Ballana, E., Bassat, Q., Baro, B., Vall-Mayans, M., G-Beiras, C., Prat, N., Ara, J., Clotet, B., & Mitjà, O. ( 2021). The spread of COVID-19 in 282 clusters in Catalonia, Spain: a cohort study. The Lancet Infectious Diseases, 21(5), 629-636. https://doi.org/10.1016/S1473-3099(20)30985-3

Xu, H., Gan, Y., Zheng, D., Wu, B., Zhu, X., Xu, C., Liu, C., Tao, Z., Hu, Y., Chen, M., Li, M., Lu, Z., & Chen, J. (2020). The relationship between COVID-19 infection and risk perception, knowledge, attitude, and four non-pharmacological interventions in the late stage of the COVID-19 epidemic in China: an online cross-sectional survey of 8158 adults. J Med Internet Res, 22(11), e21372. https://doi.org/10.2196/21372

Conflict of interest: no conflict of interest

It seems that wearing a mask is an effective measure to reduce infection; however, the reasons behind this are still unclear to me. If this conclusion is based on the particle size and pore size of the mask, it will be meaningless. For example, if I invite you to stand on the other side of the volleyball net and I shoot you with a BB gun, I guess you will be reluctant to participate because it has no protective effect on such a small projectile. I want to know whether the effect of wearing a mask is more effective, because it can prevent people's fingers from entering the mouth and nose.

Conflict of interest: no conflict of interest

Dear Editor This review has evaluated many public health measures, but has not yet evaluated the effectiveness of interventions designed to reduce the presence of viruses in the inhaled air, such as filtering, opening windows or installing ventilation equipment.

Although the impact of some of these measures on the climate may be challenging, these are potentially important considerations in the design of "anti-virus sustainability" buildings, workplaces, and residences. These factors are also potentially important correction factors for other measures, such as family isolation and social distancing/population density. In addition, ventilation may be a key determinant of the propensity of super-spreading events, and super-spreading events seem to be the main determinant of the spread of COVD19.

There is published evidence in this field, and indeed ventilation itself is a complete science. It is also the subject of hospital building regulations (4,5), WHO (1) and government guidelines (2) from all over the world. It plays an important role in ensuring the safety of employees working in COVID areas (6).

Although the fear of clinical staff working directly with COVID patients is understandable, many hospital-based COVID transmissions are likely to occur in poorly ventilated non-clinical areas. In schools, differences in the effectiveness of closure may be related to differences in ventilation or climate (and therefore opening windows), which may be the main determinant of school transmission and school return safety.

With all of this in mind, it is difficult to understand why there is no mention of ventilation, HEPA filtration (7), UV disinfection (8) or environmental CO2 monitoring has actually been carried out, especially in an article designed to inform policy? In order to properly calibrate and respond effectively to virus threats, it must be important to understand the relative effectiveness and interaction of all the different measures?

Reference 1. https://apps.who.int/iris/rest/bitstreams/1333991/retrieve

2. https://www.cdc.gov/coronavirus/2019-ncov/community/ventilation.html

3. https://www.ashrae.org/technical-resources/resources

4. ANSI/ASHRAE/ASHE Standard 170, Ventilation of Health Care Facilities

5. HBN 04-02 DoH https://www.england.nhs.uk/wp-content/uploads/2021/05/HBN_04-02_Final.pdf

6. Assess the risk of hospital-acquired infections in patients infected by aerosol-borne pathogens to medical staff. P Kalliomäki1, H Koskela1, M Waris2, JW Tang; Institute of Occupational Safety and Health 2020 https://iosh.com/media/8432/aerosol-infection-risk-hospital-patient-care...

7. Use air filtration to remove SARS-CoV-2 and other microbial bioaerosols from the air on the COVID-19 surge device Andrew Conway-Morris, Katherine Sharrocks, et al. medRxiv 2021.09.16.21263684; doi: https://doi. org/10.1101/2021.09.16.21263684

8. Davidson BL. Bare bulb upper room sterilization ultraviolet-C (GUV) indoor air disinfection for COVID-19†. Photochemistry and photobiology. 2021;97(3):524-526. doi:10.1111/php.13380

Conflict of interest: no conflict of interest

Please, as the public, can we more clearly understand which masks have been studied?

Today’s news pointed out that wearing masks is very effective in preventing the spread of Covid 19; however, there is very little information about mask types, fabrics, surgery, self-made, etc. In addition, masks can be effective only if the wearer is diligent in changing, washing, etc. We need more information.

Conflict of interest: no conflict of interest

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