Why Observational Studies shouldn’t be used to assess Respiratory Virus Interventions - Part 2

The Long Read

We have seen how past observational studies of the SARS-CoV-1 epidemic gave implausible effect estimates while randomised trials gave more conservative estimates. However, there are other reasons specific to respiratory viral transmission why observational designs should be used cautiously for informing policy.

Let’s try and put these in the context of the UK Health Security Agency (UKHSA) review provided by Lord Markham as the basis for government living with covid advice that includes ‘wearing a face covering in crowded and enclosed spaces.’ 

The review consists of 25 studies, two of which are trials included in the 2023 Cochrane review.  Here we set out a series of issues on the type and quality of evidence required to assess the effectiveness of respiratory virus interventions.

Use the right study design to answer the question.

Previous reviews by the UKHSA included ecological, descriptive, and laboratory studies. In the latest version, these are excluded, and the review reports it fo…