Discussion

Non-pharmaceutical measures taken by countries have varied depending on specific situation and socio-cultural context. As countries begin to lift some of these restrictions, different strategies have been considered. While some European countries are currently only contemplating occupational health and safety measures in the workplace and/or learning environments as part their exit strategy, other countries have recognized the positive role that serological testing might play. Given the inconsistencies in how serology testing strategies are being carried out, aligned guidance and a more coherent approach are necessary to support policy-level decision-making.
Whether a country is experiencing no burden of cases, sporadic cases, a cluster of cases/outbreaks, or community transmission, it should be continuously vigilant. Different testing strategies will yield different outcomes in understanding the true spread and severity of the virus sub-epidemics between countries and different populations at risk. Since mild/moderate or asymptomatic cases may go untested, the complete picture of the epidemiological situation cannot be fully understood in the absence of tests that can capture these cases. It is important to generate reliable and comprehensive information by conducting well-designed, scientifically, and ethically sound studies.
Sero-epidemiological population-based studies on antibody prevalence in defined communities would be essential for generating supportive data (such as prevalence, incidence, and fatality rates), and improve surveillance, monitoring, and forecasting of SARS-CoV-2 infection in populations, which could support the development of effective public health intervention strategies. At the community level, sero-epidemiological information could provide a basis for better understanding of viral spread in terms of the geographic mechanisms behind the emergence of local and regional outbreaks. Additionally, it can provide data on selective distribution among diverse populations, such as those most vulnerable and sub-populations with higher risk due to comorbidities.  Factors such as race, ethnicity, socio-economic status, and other aspects that can lead to marginalization or vulnerabilities, should be considered when performing sero-epidemiological studies and developing health policies. Conducting serology testing on vulnerable subsets of the population should be approached in a carefully planned manner so as not to place such populations at greater risk.
Serological testing can also post additional benefits to control the pandemic. Detection of mild or asymptomatic cases can provide better clarity to authorities, identifying true attack and mortality rates, as well as the potential role of immunity (including herd immunity), which can help better define and adapt policies to respond to viral patterns and develop effective prevention and control strategies. Furthermore, it could help assess the effectiveness of using non-pharmaceutical interventions in suppressing and containing the virus transmission.
Challenges may also arise from the inclusion of serological testing among testing strategies. Europe is a heterogeneous region with different social, economic, political, and cultural ethos and perspectives that can influence the use and uptake of serology testing. Further constrains may arise from insufficient supply and availability of quality tests and health workforce. An increase in demand could also outweigh the test production capacity, having further cost implications. A guidance on the role of serological testing must include actions directed at bringing awareness among policymakers and regulatory authorities. Dialogue is an essential factor that can enhance community engagement and coordinated policy action.

Conclusions