/cloudfront-eu-central-1.images.arcpublishing.com/prisa/27XJEWM4JNFS3MQEA5L4I6YDOQ.jpg "Is the number of coronavirus cases still the best measure of the pandemic?")
Is the number of coronavirus cases still the best measure of the pandemic?
Last October, the cumulative incidence (CI), i.e. the number of coronavirus cases per 100,000 inhabitants – usually measured over a period of 14 days – became the thermometer used by Spanish citizens to measure the state of the pandemic. Before then, in the first few months of the pandemic, the data point was not considered reliable as only the most serious patients were being tested for Covid-19. As testing increased, epidemiologists began to pay more attention to this indicator, but it was not until the Spanish Health Ministry published its traffic light system to measure risk that Spaniards began to understand that a CI of 500 cases is cause for concern while 50 or under is a cause for hope.
On Friday, the 14-day cumulative number of cases per 100,000 inhabitants reached 152, above the 150-threshold considered to indicate a situation of “high risk.” But with most of the at-risk population vaccinated against Covid-19 in Spain, this figure cannot be read in the same way. The CI is just one of eight main indicators and around 20 secondary ones that are used in the traffic light system to assess the level of risk in a territory. In addition to the CI, the system also takes into account to what extent the pandemic is affecting the elderly population and the pressure on Spain’s hospitals. These indicators now are playing a more important role in reflecting the risk of the pandemic – and they are not rising by a lot or are, in fact, falling.
Pedro Gullón, from the Spanish Epidemiology Society, believes that it was probably “a mistake” to only look at the CI. “Since May, when the capacity for detection was much better until the beginning of this year, it was a very good indicator, because it was very stable and it was very easy to compare certain moments and the rise in transmission,” he explains. “But as the vaccination drive has progressed, it no longer has the same meaning, because it does not translate to hospitalizations and deaths in the same way. Now it is more useful to look at other statistics, like the incidence according to age group, or the rate of hospital occupancy, positivity [the number of tests that come back positive from the total], or mortality.”
