The current policy to combat COVID-19 in the Netherlands aims at reducing the number of infections as much as possible, like in many other OECD countries. The government states as its objective to reduce the number of infected persons from its peak of 10,000 per day around 25 October beyond the current 5,000 per day to much lower numbers. In this column, we question the wisdom of this policy.
When the first wave of COVID-19 hit, policymakers all over the world had to take far-reaching decisions based on limited information, mainly from China. Across the EU, countries have been quite effective in simultaneously containing the spread of the virus with lockdowns, while providing liquidity support to firms and social assistance to workers that were hit hardest by these lockdowns. Since we are now in the middle of the second wave, we have to consider the best way to move forward from our current state, which is entirely different than in East Asia.1
There are essentially three strategies in responses to contain the pandemic (Britton et al. 2020, Acemoglu et al. 2020):
- The first strategy is to attempt to eradicate the virus altogether, as China successfully did in response to 2002-2003 outbreak of SARS. This virus eventually became extinct by strictly isolating all infected persons.
- The second strategy is the exact opposite of the first – let the virus roam freely in the population to achieve herd immunity as quickly as possible and accept the casualties as the inevitable cost. This strategy is used routinely in response to the annual waves of the flu virus.
- The third strategy is to strictly contain the spread of the virus among vulnerable subgroups of the population whose health is severely affected by a COVID-19 infection, thereby avoiding excess casualties and overburdening the healthcare system, while waiting for either a vaccine or herd immunity to end the pandemic.
Since the second strategy is not considered an option by Dutch policy makers for the COVID-19 crisis, we focus on the first and third. Reducing the number of infections is consistent with the first strategy, while it is a waste when pursuing the third. The third strategy limits the number of susceptible persons by achieving herd immunity. As long as vulnerable subgroups can be isolated, infections for the remaining population aren’t a problem. Infections accelerate achieving herd immunity, thereby reducing the time that the vulnerable subgroups are exposed.
The difference in the role of infections in both strategies can be phrased in terms of externalities. In the first strategy, an infected person imposes a negative externality on the rest of the population by being a source of further infections. This negative externality justifies government-imposed lockdown policies to internalise the externality. In the second strategy, an infected person imposes a positive externality on the population, by being immune after infection and hence contributing to a protective wall against further contagion. Counterintuitively, the government may even have to stimulate infections among the less vulnerable subgroups of the population. Ignoring this third strategy of a selective lockdown explains why Alveda et al. (2020) conclude that a strict lockdown is the only way forward for Europe and the US.
Four parameters are critical for the choice between both strategies:
1) The number of infected persons – the higher this number, the further the first strategy gets out of reach
2) The ratio of casualties to infected persons – the lower the infection fatality rate, the lower the number of casualties during the transition-period towards herd immunity
3) Heterogeneity in vulnerability by age and pre-existing medical conditions – the sharper the distinction, the better the prospects of isolating the vulnerable subgroups
4) The likelihood that there will be a working vaccine and the expected time lag until a sufficient supply will be available – the higher the likelihood, the lower the benefits of achieving herd immunity.
A comparison of the first and second wave reveals a strong shift in the first two parameters in favour of the third strategy (see Table 1). The number of positive tests per day is nine times higher at the peak of the second wave, and this increase is heavily concentrated among youth. However, the number of positive tests is a bad proxy for the real spread of the virus, since testing was limited during the first wave. The second line therefore reports the number of people with antibodies against the virus. Though less pronounced than the first line, these data exhibit a similar pattern. In contrast, the number of people in intensive care and the number of casualties is only half as high in the second wave compared to first. Moreover, if anything, the number of casualties has become even more skewed towards the elderly.
Table 1 Ratio of peak second relative to first wave for a number of statistics
Source: https://www.rivm.nl/pienter-corona-studie/resultaten
Figure 1 Numbers of positive test, hospitalized patients and casualties from the Dutch National Institute for Public Health and the Environment (RIVM)
a) Positive tests
b) Hospitalized patients
c) Hospitalised patients (alternative series)
d) Casualties
Figure 2 Age distribution of people with corona antibodies
a) As measured in April/May 2020
b) As measured in September/October 2020
Table 2 provides evidence on the third critical parameter – the degree of heterogeneity in the vulnerability of various subgroups of the population, both in terms of the risk of intensive care (IC) hospitalisation and death. The casualty risk differs by a factor of 700 between young people without pre-existing medical conditions and elderly people with pre-existing conditions.
Table 2 Age-specific risks on intensive care hospitalisation and death (per 100,000 persons)