What are the most effective anti-Covid measures? hard to define…

What are the most effective measures against Covid-19? Nearly two years into the crisis and despite the forest of research, comparisons are still difficult, as highlighted by a large study that nonetheless concluded that it is beneficial to wear a mask.

“We still lack excellent quality results on SARS-CoV-2,” the virus that causes Covid, “and the efficacy of public health measures,” sums up this study published Wednesday in the British Medical Journal (BMJ), one of the leading scientific journals. This work is important because it is one of the first studies to assess the effectiveness of anti-Covid-19 measures on a large scale.

Since the birth of the epidemic in early 2020, a wide range of measures has been tested from country to country: more or less stringent restrictions, wearing a mask, closing borders … and these options have sometimes differed over the years. Times like in France, where the authorities have shown Initially skeptical about the prevalence of mask-wearing, then I made it mandatory in many places.

A great deal of research has sought to assess the effectiveness of these measures and the BMJ study aims to explain this: it is a meta-analysis, which aggregates existing studies by weighting them according to their severity and level of requirements.

The benefit is great because this type of work gives the best possible idea of ​​the state of knowledge on a particular topic. But, in the present case, the answers are not well-defined.

70 studies

The researchers certainly concluded that some measures are likely to be effective in reducing the frequency of Covid-19 cases. Their data, aggregated from nearly 70 studies, suggests that “there is a benefit associated with hand washing, branding, and physical distancing,” that is, avoiding gathering too many people in one place.

But these effects aren’t very noticeable, and on other measures, researchers can’t even decide. “Because of the heterogeneity of the studies, it was not possible to perform a meta-analysis on the effects of quarantine and isolation, severe restrictions (as well as) closing borders, schools and workplaces,” they said. Worse, the authors were unable to review research on the effects of proper ventilation in confined spaces. However, many researchers believe that such a measure is important because the coronavirus is transmitted for the first time through the air.

However, should we conclude that all these actions are irrelevant? No. But the British Medical Journal study attests to the difficulty of finding compelling work on both. In some ways, the weakness of these studies is related to what is being examined. Unlike vaccines for Covid and potential treatments, it is difficult to form different groups from the start that will or will not implement any action.

It is difficult to isolate a factor

So most of the studies that have been compiled are looking after the fact of the frequency of Covid cases in a population that has been forced or pushed to do so.

The weakness of this approach lies in the difficulty of distinguishing what really comes from a particular measure, especially since the authorities have generally applied many of them systematically: the wearing of a mask was not recommended due to the presence of containment.

This may explain the remarkable benefits of hand washing. It doesn’t make sense because the virus doesn’t seem to be transmitted much by direct contact.

But people who wash their hands also tend to adopt other protective behaviors such as “avoid crowds, keep a distance and wear a mask,” says in a commentary also published by the BMJ, researchers who were not involved in the study. So it is difficult to isolate a particular factor. However, these commentators, including Australian professor of medicine Paul Glazio, believe it is possible to proceed to studies that are more convincing than they are now. “We need more and better research,” they assert, considering the lack of hard work a “tragedy in the pandemic.”

Julien Dore / Agence France-Presse