What are we going to know and what not with the new Health data on the pandemic
The data with which the Ministry of Health and the communities measure how the pandemic is evolving has changed. The statistic that, in fits and starts, has been sustained since the start of the pandemic is broken. But not in all indicators. We analyze what we are going to know and what we are not with the reports that are published every Tuesday and Friday. And if the data is sufficient to anticipate a worsening of the situation.
The most important change in the figures has to do with the accumulated incidence, an indicator that has been fundamental in the last two years to know how much the virus was spreading and that has been used until the sixth wave as a reference to establish restrictions. The new strategy, the result of an agreement between the regional and central governments, does not account for all cases, only the vulnerable and serious ones, so that it is not possible to know the number of positives in total and, as a consequence, neither the level of cases per 100,000 inhabitants. "The biggest limitation is that the series is broken, although de facto it was already broken since December, it was hardly interpretable with the introduction of pharmacy tests," considers Pedro Gullón, epidemiologist and professor at the University of Alcalá de Henares.
However, in each report it will be possible to see the cumulative incidence in those over 60, the people with the greatest chance of COVID-19 leading to serious illness. In this population group, diagnostic tests are still indicated, so the figures can be collected.
Are these data useful, even if they are partial? "We are starting a new series with which we are going to be able to know where the contagion curve is. If we are going up or down, if we are approaching the peak, what is the growth speed... but it cannot be compared in absolute numbers with the data that we had before, the result of the previous surveillance system, much more intensive", explains Gullón.
Knowing how much the virus is infecting older people is a specific thermometer, but not the most sensitive. "It is presumable that the cumulative incidence is lower at this age than in the general population because this older population is the best protected with three doses," completes Daniel López Acuña, former director of WHO Health Action in Crisis Situations. This expert is critical of the new system because, in his opinion, he renounces having a "finer" alert capacity by leaving aside the exhaustive accounting of cases and anticipating future waves.
The Health reports incorporate for the first time the data from the sentinel surveillance system – by samples – of respiratory viruses implemented before the pandemic. Some communities have already included SARS-CoV-2 in the data collection. The incidence that is extracted from the samples has the limitation that it does not disaggregate the type of virus that causes each infection. “It is not very specific. However, it can make us see if we may have a problem with the occupation of hospitals, it allows a good overview,” says Gullón, in the event of an eventual outbreak of infections.
With the new system it is not possible to calculate how many of the people infected by SARS-CoV-2 end up dying. I mean, how deadly is the virus. Without the data on the total number of cases available, it is not feasible to obtain the rate, explained in this interview the president of the Spanish Society of Epidemiology, Elena Vanessa Martínez. A calculation could be made with the incidence in people over 60, but it would be partial and, López Acuña warns, higher than the rates that have been recorded for the general population in recent months. Because, although the elderly are vaccinated and are the population with the highest adherence to booster doses, they also have a higher risk of dying.
The new surveillance and control strategy is aimed at taking an X-ray of severity, rather than transmission. That is why serious cases and deaths continue to be counted. There are no changes from the previous protocol. It is the indicator that, in practice, has already displaced the accumulated incidence when taking measures.
The occupancy rates of ward and ICU beds are infallible values that sound the alarm, all epidemiologists agree. Without global data on accumulated incidence, "we can find the wave once it is upon us and that reduces the possibility of early intervention," warns López Acuña. Normally, the rise in incidence is replicated two or three weeks later in hospitals. Gullón is confident, however, that both the incidence in people over 60 and the sentinel system for acute respiratory infections (ARI) will make it possible to see changes in trends in advance and act if necessary.
The new strategy is conceived as a "reversible" plan if things get worse again, "either due to a worse evolution of the severity indicators or due to the appearance of new variants," the document states. The technicians are defining what the thresholds will be to back down with the strategy. In addition, the autonomous communities must maintain the "extraordinary" deployment for the surveillance and control of COVID-19 and guarantee that "it can be reactivated" if the situation deteriorates again.