Why observational studies shouldn't be used to assess respiratory virus interventions - part 1

Why use poor evidence when better quality evidence is available?

When we first wrote the protocol of the Cochrane review “Physical interventions to interrupt or reduce the spread of respiratory viruses” in 2006, our criteria for the types of studies to be included were as follows: “We will consider individual-level or cluster randomised or quasi-randomised controlled trials. To enhance public health relevance, we wil…