How do we safely break out of Lockdown?

Any single policy alone, whether lockdown, broadening COVID-19 testing, or expanding medical capacity, will not effective in tackling the epidemic.

In fact, Lockdown is not as absolutely effective over non-lockdown as many people believe. This is because people will optimally reduce outdoor activities if they know the risk of being infected is high.

When the economy reopens after the lockdown, the infection risk is low, and so people respond by increasing their outdoor activities. We have seen this already, with crowded beaches and beauty spots, as well as the reopening of non-essential shops. This will negate almost all the effects brought by the lockdown if there are still infected individuals in the community. The one thing that is in our favour is that this is happening during Summer, when we know that the risk of viral transmission is lower than in the colder months of the year.

Broadening testing gives incentives for people to return to their normal life as fewer infected individuals are outside returning to normal behaviours. We know, however, that people do not internalise the social cost of returning to normal life, and so the situation can get worse.

The efficacy of Covid-19 testing is also a major factor. Nasal swab PCR tests may give false negative readings in 20% of cases.

Antibody tests are not much use, as only around 13% of people infected by the virus develop antibodies to it. In addition there is the issue that 50-80% of infected people are asymptomatic.

We also find that increasing medical capacity will only have temporary effects on reducing the death toll. As the cost of infection decreases, more people return to their normal behaviours, and infection increases as a result.

The most effective policy is a combination of lockdown and broadening testing: Broadening testing lowers the risks of infection, and lockdown further prevents people from returning to normal life too early. The key is a reduction of the period between being exposed to the virus and being tested positive from an average of nine days to four days. This strategy can successfully defeat the epidemic.

There is one proviso to this, and that is the length of time that immunity is granted to those who have been infected and recovered. This is a matter of great scientific debate, and the answer is not clear. If, say, immunity was granted for 7 months rather than 12 months, then the number of deaths from the pandemic would rise by 23% according to modelling.

Without any policy intervention at all from health agencies and government, it is likely that the pandemic would last for another two years.