Coronavirus: could Sweden’s gamble pay off?
Stockholm may have more in common with Bulawayo than Milan
The Swedes are doing it differently. Resisting warnings to conform to the international consensus, prime minister Stefan Löfven has placed his trust in the common sense of his citizens, while denying that national policy is to boost herd immunity.
The Swedes have, in fact, taken sensible measures to slow the rate of infection and protect the most vulnerable. Those who have underlying health conditions and everyone over 70 have been advised to stay at home, and large gatherings (initially over 500, now over 50) have been banned. Most significantly, some but not all schools have been closed, the choice having been informed by both education and medical considerations. While universities and high schools have adopted a remote learning model, primary schools remain open because the youngest children cannot effectively be taught online and are at the least risk of developing symptoms.
The wisdom of the Swedish approach appears to be confirmed in two very recent papers, both published without peer review on 27 March. Both also suggest that the Swedes may have extraordinary good luck.
The first paper, “Epidemiological tools that predict partial herd immunity to SARS Coronavirus 2“, by two Japanese researchers based at Kyoto University, has modelled the spread of the two major types of SARS-CoV-2 (SARS Coronavirus 2, the virus that causes COVID-19). These are identified as the S type, which is the older (ancestor) variant of the virus, and the L type, a more recent mutation that appears to be transmitted far more quickly.
The identification of the two types of the same novel coronavirus, both circulating in Wuhan, was first made by a team of Chinese scientists in a paper published on 3 March, in the National Science Review. They noted that the S type appears far more likely to be asymptomatic – many more of those who contract it are unaware of that fact and show no symptoms. For that reason, exposure to the S type prior to the emergence of the L type may have allowed some communities, both inside and outside Hubei province, to develop herd immunity.
Communities of individuals with immunity are predominantly found elsewhere in China, but also may be in Japan, the unforeseen result of allowing almost 2 million Chinese visitors into Japan between November 2019 and February 2020. So far, Japan has had amazingly few identified cases – just 1,693 on 29 March – which may reflect an abundance of prior mild or asymptomatic cases caused by the S variant of the virus. This had the notable, and diagnostic, side-effect of ending an influenza epidemic that was at the time in full flow. As the researchers write, “Type I interferons induced by S type SARS-CoV may interfere with infection by flu virus.”
The terrible implication of this conclusion, if correct, is that the Trump administration’s swift move to impose bans on visitors from China in late January may have exposed the USA to the L strain before the less potent S strain had been introduced. Sweden has not yet introduced any travel bans.
The Trump administration’s swift move to impose bans on visitors from China may have exposed them to the L strain before the less potent S strain had been introduced
A map that accompanies the paper predicts the severity of coronavirus in each region across Europe, and this suggests that Scandinavia, the Baltics, and Ireland will be among the least severely affected. The UK, for reasons that are not set out in the paper, is predicted to be among the most severely affected. Sweden is lucky to be among those few countries where “policies that balance social closure and population immunity are desirable”.
The second paper to support the Swedes’ stance is “Age-dependent effects in the transmission and control of COVID-19 epidemics“, published by researchers at the London School of Hygiene and Tropical Medicine (LSHTM). It explores the implications of the widely observed fact that children do not appear to suffer anything but mild symptoms, or remain asymptomatic, when they contract the virus. The researchers conclude that, while children are probably infected at the same rate as adults, they do not spread the virus at the same rate.
To put it crudely (as the LSHTM researchers do not) school-age child are less likely to cough or sneeze the virus onto surfaces and others. And what they do spread will be far less potent.
This runs contrary to the general rule, applied in cases of epidemic influenza, that children are both rapid spreaders and especially vulnerable. It is this well-established understanding that has driven the closures of schools, and in the case of coronavirus it may be entirely the wrong move to have taken.
The LSHTM researchers do not argue for developing herd immunity through leaving children in schools. But they do observe that school closures will have, and in studied cases have had, a negligible impact on slowing the spread of coronavirus. “We found that school closures decreased peak incidence slightly for influenza-like infections, and delayed the peak substantially.” However, and importantly, “For COVID-19 epidemics, the delay and decrease was smaller, and this was especially the case in Bulawayo, which has the highest proportion of children.”
A major conclusion of the paper is that countries and regions with low median age (i.e. lots of children, such as in Bulawayo, Zimbabwe) will suffer far less pronounced peaks of infection than those who high median age, such as Milan. Italy has the second-highest median age (45.5) in Europe, after Germany.
Sweden is again, in this regard, lucky. It has one of the lower median ages in Europe (41.2). It seems, therefore, that Stefan Löfven was wise to respond to the crisis in a manner that suits Swedes, their national culture, and local conditions. He has listened to his public health experts and followed their advice. To that end, the Swedes can now draw upon the latest research to contend that closing primary schools would not only fail to slow the rate of infection substantially, it might also be counter-productive medically. It would be a remarkable and unexpected benefit indeed if children who have contracted COVID-19 were protected from flu, even for one year, since seasonal influenza hospitalizes and kills thousands of youngsters each year around the world. This, however, is not yet certain.
More certain is the reality that closing schools is devastating for the education of young Swedes and for the country’s economy. It is not a move that should be taken as a first measure, and all efforts must be made to reopen schools as soon as possible.
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