What works, and what doesn't, against Covid-19

A planetary-scale experiment is underway. Never before have so many countries been both subjects and objects of experimentation simultaneously. The first great pandemic of the 21st century has forced the adoption of a battery of non-pharmacological measures to limit the spread of the SARS-Cov2 virus and thus reduce hospitalizations and deaths due to Covid-19. In the experiment, each country or each region is applying a set of measures, which it considers most effective. And a research team, combining four different methodologies, has estimated the degree of effectiveness of each measure by virtue of its ability to reduce the multiplication of the virus.

Those that most effectively contribute to reducing the spread of SARS-Cov2 they are the ones that prevent people from coming together and those that limit their movements. For these purposes, the suspension of meetings of not too many people (less than 50 people) for a long time (in stores, restaurants, bars, work centers), the closure of educational centers (mainly of students between 10 and 19 years old) , curfews, limitations to travel between countries, confinements, and suspension of mass events.

Some of these measures have very negative effects on health. The closure of schools potentially leads to worse nutrition, stress and social isolation for those affected. Home confinement causes increased family violence against women and minors. Furthermore, it reduces access to health care, which even increases mortality. As if that was not enough, the real effectiveness of this measure is not clear, because it is usually implemented at the same time that other very effective ones are adopted. For this reason, the authors of the research do not consider it advisable except, perhaps, if it is implemented in very early phases of the expansion of the pandemic.

Given the adverse effects -also on rights and freedoms- of the previous measures , governments have considered and applied alternative options. And it turns out that, curiously, non-intrusive measures have shown great effectiveness, even greater than that of some restrictive ones. This is the case of the availability of masks for everyone; campaigns to inform citizens, specific to each type of recipient; or financial aid to people with few resources or in a vulnerable situation so that they do not suffer financially if they cannot go to work or maintain their economic activity. It is also surprising that the mandatory implementation of certain measures is hardly more effective than communication campaigns that promote the adoption of these same measures on a voluntary basis.

On the contrary, actions to which a lot of importance are not sufficiently supported. For example, systematic cleaning and disinfection of surfaces does not appear to be justified; limitations on public transport, since vehicles do not appear to be enclaves that promote the spread of the virus; or the closure of parks or museums. The study has not been able to contrast the effectiveness of the campaigns to detect infected people, and trace and isolate their contacts, probably because most of the data was obtained in March and April, when most countries experienced the highest incidence of the epidemic and they still lacked good tracing systems.

The planetary experiment has shown that what we think we know today may not be valid tomorrow, because knowledge is contingent and always provisional. Science corrects itself. That is the reason why we move forward and make better and better decisions.

Source: Haug, N., Geyrhofer, L., Londei, A. et al. (2020) Ranking the effectiveness of worldwide COVID-19 government interventions. Nat Hum Behav doi: 10.1038 / s41562-020-01009-0

Note : For those interested, Elhuyar has published a review of this same work in Basque language.

Addendum (on the importance of local ventilation) : The results and conclusions of the study by Haung et al (2020) are based, as indicated in the text, on data coming from the months of March and April. In those months there was the conviction that the main routes of contagion were, on the one hand, contact with surfaces (hence the importance given to cleaning hands and not touching the face, for example); and on the other hand, the droplets that are expelled when coughing or sneezing (which is why it began to be recommended to maintain a distance of 2 m between people and, later, the use of masks in closed spaces or, in general, very crowded). But in those months, the ventilation of the premises was not recommended because there was insufficient evidence that aerosols could be an important route of infection. The first data supporting this possibility began to be published in the scientific press at the end of April . As of May, it began to recommend the ventilation of closed places. In June, there was already sufficient evidence in this regard. And as of July, there were already many researchers who thought that the risk of airborne transmission of the coronavirus was being underestimated . In short, the work reviewed here does not consider the ventilation of the premises as a potentially effective measure for the simple reason that in the months of March and April, due to the lack of firm evidence in this regard, it was not promoted. During the second wave, however, given the overwhelming evidence in this regard it is recommended to keep the premises well ventilated in general.

About the author: Juan Ignacio Pérez ( @Uhandrea ) is professor of Physiology and coordinator of the Chair of Scientific Culture of the UPV / EHU

The article What works, and what doesn't, against Covid-19 has been written in Cuaderno de Cultura Científica .

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