Letters | With talk of a sixth Covid-19 wave in Hong Kong, can we trust data models?
- Given that different assumptions made by researchers will generate very different projections, claims made by health experts should be accompanied by a disclosure of assumptions made in the research

Projections using mathematical modelling involve assumptions and estimates made by researchers. Previous reports published by the HKU team clearly stated the assumptions and estimates made, that is, the basis on which their predictions were made. For example, one of the assumptions influencing the predicted outcome was the estimated effectiveness of tightened social restrictions announced by the government.
Different assumptions made by researchers will generate very different projections. It is important that any claims made by health experts – like the one related to the sixth wave – should be accompanied by a disclosure of assumptions made in the research. The lack of such transparency will only preclude informed discussion of new findings.
Predictions can go wrong, especially when they involve changing human responses and environmental factors, coupled with a new, evolving virus. In the United Kingdom, several models by leading scientists have been criticised for overestimating the number of daily infections and deaths at different phases of the pandemic.