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The metrics of COVID-19

“Measurement is the first step that leads to control and eventually to improvement. If you can’t measure something, you can’t understand it. If you can’t understand it, you can’t control it. If you can’t control it, you can’t improve it.” These words by H. James Harrington, building on the classic quote by Peter Drucker, the father of management consultancy, explain our collective fascination with metrics in the era of COVID-19. The challenges for us are that what is easy to measure may not be the most valuable measurement to make, and different metrics may be helpful in different situations. Symptom trackers, such as Zoe, provide rapid insights at global scale but are subjective, may be confused with other diseases and many have no symptoms at all. International comparisons of confirmed cases may be confounded by differences in the availability of tests and different screening strategies for high-risk groups such as shielded populations and care homes. A focus on excess deaths provides an objective measure of the overall impact of the pandemic, direct and indirect – but it is far too late a measure to use for controlling localised outbreaks.

One other metric that has been tracked by governments across the world since February has been hospitalisations. It is not without its problems. The number of beds in each country is relatively fixed in the short term, although we have seen how capacity can be increased by use of the private health care sector or the construction of new hospitals such as the Nightingales. At the height of the first wave, triaging restricted admissions to those who would benefit most. For now, capacity in hospitals and ICUs is sufficient or at least no worse than it was before. Hospitalisations provide a useful comparative metric of the serious impact of COVID-19, both early enough and with sufficient information on the individual cases to be useful. Insights and data from cohorts, such as the international ISARIC study now covering 60,000 patients, will improve survival and help us support long-term health needs of COVID-19 survivors.

This international comparison of hospitalisations using data from the European Centre for Disease Control (ECDC) and COVID-Net in the USA show the exponential growth and decay in many countries over the last 6 months. We can see the surge in June/July in the USA, and how a number of countries are starting to see increasing demand. But the rates are still low, and reflect the spread of the virus in younger populations who are less likely to need hospital care.

We are measuring. Our understanding grows by the day. How we recover as societies depends on whether we trust that control and improvement are within reach.

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