The curfew probably had little or no effect on the course of the corona epidemic in the Netherlands. That is the preliminary conclusion of Sake de Vlas, professor of infectious disease modeling at Erasmus University in Rotterdam. He did his own research after NRC approached him about the recent statement by Ernst Kuipers, chairman of the National Network Acute Care, that the curfew had “no effect” on hospital admissions. De Vlas sees his research as a “creative start to an evaluation” of the curfew.
Curfew was introduced on January 23 and abolished just over three months later, April 28. The measure has led to little or no decrease in hospital admissions, according to the figures from the hospitals. “The hospital inflow data of Covid-19 patients does not show a pattern consistent with an effective curfew. The effect is questionable, ”says the researcher.
The key to De Vlas’ finding is the insight that the curfew was introduced everywhere in the Netherlands at the same time to halt the advance of the more contagious British variant, but that the extent of this advance varied by region. In the east and north of the Netherlands, the British variant was introduced three weeks later than in the Amsterdam region, “where there is a lot of interaction with the United Kingdom”. For example, from January 21 to February 4 in Twente, only 11 percent of the infections concerned this variant.
‘No kink down’
In the east and north, therefore, a decrease in the number of patients could have been expected first, as this decrease could not be offset by an increasing number of infections from the British variant. “The curfew works as a counterforce to the emergence of the British variant, but if there is not (yet), then the effect of only the curfew should become visible by a downward nod,” said De Vlas. “The four regions with a likely late emergence of the British variant do not show a clear downward nod at first.”
De Vlas is not yet certain of his conclusions: this trend is less clear in two of these regions. De Vlas ‘would like’ to see more regional studies. To the objection that rural people may come into contact with fewer people than city dwellers, De Vlas says: “Most dissemination goes through family, work, school and friends and that is comparable everywhere.”
Ernst Kuipers’ statement was disputed by other scientists, who argued that the curfew, along with the urgent advice to have only one visitor per day per household, is believed to have prevented a much higher number of sick people. That this cannot be proven was called the ‘prevention paradox’; you don’t know what would have happened if curfew had not been put in place.
In any case, the curfew has given the police a lot of extra work and cost citizens a lot of money: 95,000 fines were handed out for violations. Outgoing minister Ferd Grapperhaus (Justice, CDA) later chastised Kuipers about his statements. Kuipers now says: “Certainly there were 200 admissions a day before curfew, two weeks after that, and four weeks after that too. Conclusion: that curfew doesn’t do that much. ”
Professor De Vlas points out that Kuipers’ critics are based on reports from the RIVM that shortly after the introduction of the curfew, two-thirds of all infections in the Netherlands concerned the British variant. In retrospect, the results of laboratories in various parts of the Netherlands show, according to De Vlas, that this was too high an estimate. “The first measuring points (until January 8, especially from Amsterdam) gave rise to too much panic about the rise of the British variant in retrospect.”
From April onwards, the so-called reproduction rate and the number of hospital admissions started to decline again. The researcher cites not so much the curfew as possible reasons for this, but rather the increasing number of people with immunity against the coronavirus, perhaps also the seasonal effect and the increased number of vaccinated people. In addition, there is the effect of what the researcher describes as ‘heterogeneity’; the number of people who become infected can vary significantly by region and by different characters. For example, people who maintain fewer contacts anyway are less likely to be infected than people who maintain many contacts; that could dampen a rise of the corona epidemic over time.
Marc Bonten, professor of molecular epidemiology of infectious diseases and member of the Outbreak Management Team (OMT) calls De Vlas an “excellent researcher” and “a good colleague”, but does not just agree with him on this matter. “It’s an interesting hypothesis, but the issue is quite complex. No one can say for sure that the curfew is working, or has not worked. ”
He argues that at the start of the advance of the British variant, the Netherlands had ‘very little information’. “There was great uncertainty about the distribution in the regions and about how quickly the British variant would displace the old variant.” At the beginning of April, the British variant had supplanted almost all other variants of Covid-19 in the Netherlands. According to Bonten, there were “certainly regional differences” in the beginning, but little research has been done to show variants. Bonten thinks that it is quite possible that the curfew, together with other measures, has indeed contributed in steps to a decrease in the infection rate R, from 1.3 to 1.0. “That’s about the effect you might expect from a curfew beforehand.”
According to the RIVM, research by the so-called relocation panel shows that the curfew has led to a reduction in the number of contacts, by 10 percent. Minister Grapperhaus also mentioned this decrease. De Vlas nuances its importance. He does not rule out that participants in this study are ‘more docile’ than the average Dutch person in complying with the rules and display ‘socially desirable behavior’. Groups that ignore curfews can even put them at a “higher risk” of being infected, “such as youngsters who spend all night long.” Finally, De Vlas points to ‘extra processes that are difficult to measure’, such as full trains shortly before curfews and less staggered visits to supermarkets. Ernst Kuipers also thinks this has limited the possible effect of the curfew. “Student parties did not stop at half past one in the morning but at half past four,” he says.
Also read: Above all, we have to hope that the curfew works, says Jaap van Dissel
Despite the disappointing results, according to De Vlas, it was “a logical decision” to introduce a curfew to stop the British variant, which appeared to be making very rapid progress. In addition, foreign research had shown that a decrease of about 10 percent in the number of infections could be expected due to the curfew and the one-visitor scheme.
‘Analyse is complex’
But, says De Vlas, “what works for other countries does not have to work for the Netherlands.” For future considerations about introducing a curfew, it is ‘important’ to evaluate the effect of the measure, he says. His current research is “a first step” to this end.
Despite repeated requests, the RIVM says it cannot respond substantively. “At the moment we are busy with the current situation,” said a spokesman. “We had estimated the effects of the curfew in advance based on experiences abroad. Incidentally, often in combination with a different package of measures than in the Netherlands. The analysis of the effect of the curfew and the one-visitor scheme is quite complex. We are going to do this, but it may take a while. ”
A version of this article also appeared in NRC on the morning of May 14, 2021