Throughout the pandemic, most individuals act without knowing their health state, which naturally affects their willingness to social distance. Recent research suggests that this uncertainty can be quite adverse, by increasing contagion and raising COVID-19 related deaths. However, part of the uncertainty can be reduced by antibody testing. By revealing that susceptible and asymptomatic individuals are not immune, antibody testing reduces their social activity lowering the scale of the pandemic.

The research was carried out by Dr Luis Guimaraes, Lecturer in Economics from Queen’s Management School, and recently published in the Journal of Mathematical Economics.

Dr Guimaraes built an economic model of epidemics extending the standard SIR epidemiological model, widely used to guide policy during the pandemic, to include individuals’ choice of social distancing.

In the model, individuals react to the information about infections. When infections rise, they realise the increased risk of infection and lower their social contacts, which reduces the effective reproduction number, Rt. However, if susceptible individuals are unsure of their health state and erroneously believe to be immune, they constrain their social activity by less than otherwise. In this regard, by informing individuals, antibody tests reduce average social activity and permanently lower COVID-19 related deaths. When the model is calibrated to capture the costs of social-distancing and of infection as well as the basic reproduction number, R0, Dr Guimaraes found that antibody testing could prevent approximately 12 per cent of COVID-19 related deaths within 12 months.

Speaking about the findings Dr Guimaraes explained: “This research suggests that there can be sizeable gains in terms of lives saved from conducting largescale antibody testing. The benefits of these tests are particularly large for those that cannot work from home in areas in which many are estimated to have been infected like London.”

The Covid-19 pandemic has virtually halted the UK economy and resulted in over 120,000 people in the UK and over 2.4 million people worldwide losing their lives due to the virus (February 2021).

The UK Government and countries around the world restricted movement, imposed lockdowns and quarantines, forced the closure of businesses, and increased the scale of viral testing and contact-tracing in order to contain the virus.

Antibody testing can have major benefits. Firstly, in understanding the extent of the pandemic, the infection-fatality rate, the duration of immunity, and the proportion of the population who are asymptomatic. They have been and are currently being conducted in several countries, including the UK, and have helped to guide policy. Secondly, by identifying immune individuals, large-scale antibody testing may facilitate reopening the economy after a lockdown.

“There is also another, not as evident, reason to support largescale antibody testing. By revealing that susceptible individuals are not immune, antibody testing increases their social-distancing, lowering the scale of the pandemic,” said Dr Guimaraes.

Most individuals infected with COVID-19 do not develop symptoms or only develop mild ones, most of those that were infected are unaware of the infection, which makes it very difficult to identify infected individuals and prevent contagion.

The Office for National Statistics (ONS) (June 2020) estimated approximately 5.4 per cent of the English population had been infected, but less than 15 per cent of those had been diagnosed by June 2020.

“Put differently, this means during the first wave of infections, 85 per cent of infected individuals were not diagnosed. Past infection is associated with, as least, temporary immunity, and so many would have recovered and became immune (and likely still are), unaware of their immunity. Therefore, there is uncertainty about the susceptibility to the virus," added Dr Guimaraes.

“This uncertainty unlikely prevails for those that worked at home and effectively socially distanced however there is much uncertainty for those that could not stay at home (e.g., for work-related reasons), especially in cities or regions with high infection rates. Faced with such uncertainty, these individuals naturally wonder whether they were infected but asymptomatic in the past and, thus, whether enduring the costs of social distancing is warranted. This shadow of a doubt might lead susceptible individuals to be less cautious, reducing social-distancing and increasing SARS-COV-2 contagion.”

Largescale antibody testing would help to identify immune individuals, allowing them to enjoy the benefits of social activity. But, critical for contagion, negative antibody testing would identify those that are not immune, compelling susceptible or vulnerable individuals to be more cautious and, thus, increase social distancing.

The full paper is available here: https://www.sciencedirect.com/science/article/abs/pii/S0304406821000239

ENDS…

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