The starting point varies on a daily basis between 14 and 20 March. Face masks increase compliance with physical distancing recommendations during the COVID-19 pandemic. If we look at the estimated differences by age groups, SI Appendix, Fig. We therefore also study treatment effects for other individual regions that introduced face masks earlier than other regions. Some field observations in this respect would be very useful, especially across federal states in Germany and worldwide. 6 and 7 argue that aerosols (as opposed to larger droplets) are filtered only by high-quality masks. Generally, these sensitivity tests underline the robustness of the estimated treatment effect for Jena. COVID-19 spreads mainly from person to person through respiratory droplets. Le premier ministre italien Giuseppe Conte a annoncé dimanche soir une nouvelle série de mesures pour endiguer la recrudescence de la COVID-19, … As pointed out in ref. Earlier work includes ref. The population in this pioneer region might have reacted very strongly to the mandatory introduction of face masks by taking the other imposed public health measures and hygiene rules (washing hands, limiting interactions, staying at home more, etc.) Hence, the introduction of face masks reduced the number of COVID-19 cases byreduction over δ days = Icontrolever(T+Dm+δ) − Imaskever(T+Dm+δ)Icontrolever(T+Dm+δ) − Icontrolever(T+Dm)∗100%.[1]. Theoretical effects of face masks on the number of infectious individuals I(t) and on the accumulated number of infectious individuals Iever(t). If we resort to the estimated incubation and reporting lag as shown in SI Appendix, section A.3, this result supports our main SCM findings that the relative reduction in the cumulative number of COVID-19 cases is mainly attributable to the timing of introducing face masks. This result provides further empirical support for a relevant effect in the case of Jena. Waiting 10 or 20 d then allows us to quantify the effect of the intervention. If you are able to wear a mask, remove your mask if it gets moist from sweat and replace it with a clean mask. Copy link. Wearing a mask helps protect those around you, in case you are infected but not showing symptoms. Abkarian M, Mendez S, Xue N, Yang F, Stone HA. C and D plot the estimated average treatment effects, that is, average reduction in the cumulative number of COVID-19 cases (black solid lines) over time joint with 90% confidence intervals (gray dashed lines) for the two samples. We accordingly alter the imposed lag structure for predictors that have a time dimension, that is, the number of cumulative and newly registered COVID-19 cases. Second, as described in Method and Data, Jena is a fairly representative region of Germany in terms of COVID-19 cases. Hexagon Manufacturing Intelligence exists to help customers rapidly transform their manufacturing business by enabling them to work at the speed they need to, while inspiring complete confidence in the reliability of their processes and the quality of their output. They considerably helped in improving this analysis. Ref. ↵##We implicitly assume that compliance to rules in Germany is sufficiently homogenous. Order Now. As a first guess and assuming a compliance of 100% in our treated regions, one would expect that a reduction in compliance by x% of the population leads to a reduction of the effects of masks by x%. Similar to SCM, the DiD approach estimates treatment effects by contrasting changes in outcomes between a pretreatment and treatment period for treated and nontreated (control) regions. Our findings indicate that the early introduction of face masks in Jena has resulted in a drop in newly registered COVID-19 cases of around 75% after 20 d. Put simply, if the control region observes 100 new infections over a period of 20 d, the mask region observes only 25 cases. Now imagine we want to quantify the effect of face masks. S2). The Centers for Disease Control and Prevention (CDC) cannot attest to the accuracy of a non-federal website. DiD estimation also relies strongly on the validity of the parallel trends assumption: It requires that treated and control regions would have followed parallel trajectories over time if treatment had not occurred. Les réponses à vos questions sur le coronavirus Covid-19. Public health data have been deposited in FigShare (https://doi.org/10.6084/m9.figshare.13065920). Treatment effects are identified by comparing the development of outcomes in treated and control regions during the treatment period. Les mesures d'hygiène et de prévention face au Coronavirus COVID 19. In cold weather, masks may become wet from breathing, snow, or other precipitation. Relative to the average number of cumulative COVID-19 cases on 11 May in control regions (317.9), this amounts to a reduction of 8.9% in the cumulative number of COVID-19 cases and a reduction of 51.2% in newly registered cases. The number saw its minimum of 20 in May 25, which was the day when the state of emergency was withdrawn. COVID-19 is thought to have a significant proportion of mildly symptomatic or asymptomatic infections 37,38,39, and therefore infectious persons unaware of their status may continue to … In B, the donor pool is reduced to comprise only larger cities (kreisfreie Städte). The figure shows the average development of the cumulative number of COVID-19 cases for treated units (defined as all regions that introduced face masks on or before 22 April), for their synthetic control groups and estimated treatment effects. Cotton face masks are more effective against Covid-19 than synthetic coverings as the humidity in your BREATH helps the fabric to trap particles, … We consider the timing of mandatory face covering as an exogenous event to the local population: Masks were imposed by local authorities and were not the outcome of some process in which the population was involved. 5. The authors declare no competing interest. Masks may not be necessary when you and the person you are caring for are outside and away from others, or with other people who live in the same household. 1A clearly shows a gradually widening gap in the cumulative number of COVID-19 cases between Jena and its synthetic control group. Protect yourself and others by making these 6 simple precautions your new habits: Clean your hands often. Change a mask when it becomes wet. 6 as Icontrol(t). “Einschätzung vom Freitag, 20. L'Afrique face au Covid-19 : vous avez dit « mesures sociales » ? Learn more about our COVID-19 response. Depending on the region we consider, we find that face masks reduced the number of newly registered severe acute respiratory syndrome coronavirus 2 infections between 15% and 75% over a period of 20 days after their mandatory introduction. Si vous avez des difficultés pour entendre ou parler par téléphone en raison d’un handicap, vous pouvez vous rendre sur l'espace de contact ouvert dédié aux personnes sourdes, malentendantes ou aveugles . CDC recommends wearing a mask while dining in a restaurant, particularly indoors and when speaking with restaurant workers and servers, except when actively eating or drinking. The European Council and the Council of the EU are served by a single administration, the General Secretariat of the Council (GSC). Mitigating the spread of COVID-19 is the objective of most governments. Consider using an antifogging spray that is made for eyeglasses. They are displayed in Fig. Average treatment effects for the introduction of face masks with multiple treated units. EN DIRECT. Jena implemented 27 of these 40 either earlier than Thuringia or on its own. Create beautiful designs with your team. Ma QX, Shan H, Zhang HL, Li GM, Yang RM, Chen JM. While supplies last. 4B highlights, such an avoidance effect may be particularly important in larger cities with higher population density and accordingly higher intensity of social interaction§§. They can be worn over a mask. Implications of these requirements for our analysis are discussed in SI Appendix, section B and we apply a series of robustness tests to check if the requirements hold in our data settings (reported in Robustness Checks). The visual inspection of the development of cumulative COVID-19 cases shows that the trend development of the synthetic control group is very similar to Jena before the treatment, indicating a good fit.‡ The difference in the cumulated registered COVID-19 cases between Jena and its corresponding synthetic control group after the start of the treatment on 6 April can be interpreted as the treatment effect on the treated [see SI Appendix, section C.3 for (post)estimation details]. We therefore follow the spirit of ref. We also employ a standard SIR (susceptible–infected–removed) model and undertake an analysis of the distribution of the lag between infection and reporting date. As economic costs are close to zero compared to other public health measures, masks seem to be a cost-effective means to combat COVID-19. 10 conducts a systematic review and meta-analysis. CDC recognizes there are specific instances when wearing a mask may not be feasible. Fighting this disease is our joint responsibility. A cloth mask also offers some protection to you too. We set out by analyzing the effect of face masks on the spread of COVID-19 for a comparative case study of the city of Jena. Thank you for your interest in spreading the word on PNAS. We do not capture any email address. We estimate that costs (of households only) for face masks amount to 1.4 to 2.5% of disposable income.]. After face masks became mandatory between 1 April and 10 April 2020 the number of new infections fell almost to zero. This change in behavior is known as the Hawthorn effect. Biological fluid dynamics of airborne COVID-19 infection, The economic costs of conflict: A case study of the Basque Country, Synthetic control methods for comparative case studies: Estimating the effect of California’s tobacco control program, Using synthetic controls: Feasibility, data requirements, and methodological aspects, Estimating the population-level impact of vaccines using synthetic controls, Fundamental protective mechanisms of face masks against droplet infections, A schlieren optical study of the human cough with and without wearing masks for aerosol infection control, Face coverings, aerosol dispersion and mitigation of virus transmission risk. Visit CDC’s, When you are around people who do not live with you, including inside your home or inside someone else’s home, Inside your home if someone you live with is sick with. To this end, we built a database for all public health measures in Jena and Thuringia and for face masks in all other federal states. 3A denoted “Synth March 14.” It shows the cumulative number of COVID-19 cases for a synthetic control group for Jena extracted from the full donor pool under the assumption that some treatment had started on 14 March. One-time Connection Service Fee ($45) applies. As SI Appendix, Fig. Bring extra medical procedure masks with you in case you need to change out a dirty or wet mask. Respiratory droplets travel into the air when you cough, sneeze, talk, shout, or sing. 8 that was recently extended by ref. The timing of mandatory face mask wearing in German federal states (Top) and individual regions (Bottom). Examples of earlier implementation include the closing of bars, cafés, and restaurants or quarantine rules for travelers returning home. News from the US, Europe, Asia Pacific, Africa, Middle East, America To establish this counterfactual, the SCM approach constructs a synthetic control group as weighted average of regions in the donor pool of controls. Avoid touching your eyes, nose, and mouth when removing it. A wet mask is harder to breathe through, is less efficient at preventing your respiratory droplets from reaching others, and allows for more respiratory droplets to escape around the edges of the mask. Arguments in favor of the high 70% stress that Jena introduced face masks before any other region did so. We quantify the effectiveness of face masks by employing the synthetic control method (SCM; refs. CDC is currently studying these factors. Visit CDC’s Improve the Fit and Filtration of Your Mask to Reduce the Spread of COVID-19 webpage to learn more. Hence, it provides the most clear-cut quasi-experimental setting for studying its effects. Again, this timing is in line with our above argument that a sufficiently long incubation time and testing lags need to be considered in the evaluation of treatment effects.††. By 29 April face masks had become mandatory in all German regions. Although the estimated average treatment effect is smaller compared to the one found for Jena, it is still statistically significant and sufficiently large to support our point that wearing face masks is an effective and cost-efficient measure for fighting COVID-19. (Details on the construction of the synthetic control group and SCM estimation are given in Method and Data.) Online ISSN 1091-6490. Identification of the face mask effect therefore needs to take the timing of other public health measures into account. The figure shows the empirical development of the cumulative number of COVID-19 cases in Jena (treated region, black solid line) and the estimated development in different synthetic control groups over time. Measures imposed by Jena only include the complete closing of hotels (in contrast to closing of hotels for tourism only in Thuringia) and a curfew (which lasted for only 2 wk, though). Studies show that masks reduce the spray of droplets when worn over the nose and mouth. Yet, the gap to the synthetic control significantly widens only ∼10 to 12 d after the announcement and then grows considerably over time. We study the effectiveness of face masks. COVID-19 spreads primarily from person to person. ↵#See local newspaper reports, for instance ref. It is of utmost importance to understand how effective various public health measures are. Medical procedure masks are single-use masks that are not made of cloth and are not designed to be washed or laundered. We estimate overall effects for these variables together with disaggregated effects by age groups (persons aged 15 to 34 y, 35 to 59 y, and 60+ y). CO2 molecules are small enough to easily pass through any cloth mask material. If you have respiratory conditions and are concerned about wearing a mask safely, discuss with your healthcare provider the benefits and potential risks of wearing a mask. The incremental DiD results also support our main SCM findings in terms of the magnitude of the treatment effect. Le gouvernement a annoncé vendredi 12 février le durcissement des mesures contre la propagation du Covid-19. Note: N95 respirators approved by CDC’s National Institute for Occupational Safety and Health (NIOSH) should not be used outside of healthcare settings because they should be reserved for healthcare personnel. If they are unable to wear a mask, ask their healthcare provider about alternative ways of reducing transmission risk, Remove their mask before sleeping, napping, when they may fall asleep (such as in a car seat or stroller), and in situations when continual supervision is not possible. These are low growth rates compared to the early days of the epidemic in Germany, where daily growth rates lay above 50% (20). Looking at average treatment effects for all other regions puts this result in some perspective. In contrast, the respiratory droplets that carry the virus that causes COVID-19 are much larger than CO2, so they cannot pass as easily through a properly designed and properly worn cloth mask. The database indicates that our results indeed capture the effects of face masks and not of other public health measures. S2, Jena and Thuringia passed at least 40 public health measures before the end of April 2020. Do NOT put a plastic face shield (or a mask) on newborns or infants. K.W. In B, the donor pool is reduced to comprise only larger cities (kreisfreie Städte). The time path I(t) of infections individuals in this (synthetic) control group is displayed in Fig. ↵†††We chose T = 29.5 as this yields a date when masks show an effect in the data on T + Dm = 40 where the epidemic is already beyond its peak in our simple model. How to obtain the confidence interval from a P value, Comparative politics and the synthetic control method, The Synth_Runner package: Utilities to automate synthetic control estimation using synth. Use Canva's drag-and-drop feature and layouts to design, share and print business cards, logos, presentations and more. The introduction of mandatory face masks and the associated signal to the local population to take the risk of person-to-person transmissions seriously apparently helped considerably in reducing the spread of COVID-19. We study the sensitivity of our estimates with respect to the length of the training and validation period before the start of the treatment. ... De ce fait, ils ne sont donc pas éligibles à l’exonération Covid-19. The donor pool of control regions (all regions in Germany and only larger cities, respectively) is specified such that the minimum time lag in the introduction of face masks between treated and control regions ranges between 5 and 13 d. The results, visible in Fig. People age 2 and older should wear masks in public settings and when around people who don’t live in their household.​, Wear a mask inside your home if someone you live with is sick with, Wash your hands with soap and water for at least 20 seconds or use. We find statistically significant and sizeable support for the general perception that the public wearing of face masks in Jena strongly reduced the number of incidences.

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