The paramount importance of serological surveys of SARS CoV 2 infection and immunity
In this Commentary I will argue that repeated large scale SARS CoV 2 antibody testing of randomly selected populations is a necessity during lifting of coronavirus pandemic restrictions. The current pandemic of COVID 19 caused by the coronavirus SARS CoV 2 is being managed worldwide with different levels of social distancing and enhanced hygiene. The overall objective is to flatten the epidemic curve of symptomatic SARS CoV 2 infections [1] below the level of maximum hospital capacity, in particular of the capacity of intensive care units. This worldwide strategy of reducing social mixing has enormous impact on the economies of countries urging policymakers to contemplate how to open up sectors of the economy or the economy as a whole. The key question is: what data do we need to avoid a second wave of the pandemic larger and more extensive than what we have seen sofar? The general idea among epidemiologists and virologists is that a second wave that hits us late allows us to strengthen the infrastructure to track and trace contacts and contain the epidemic in such a way that the capacity of the health care system is more than sufficient to care for the severily ill. Most governments are wrestling with the principal choice between two epidemiological alternatives: primarily preventing infections versus primarily preventing the life threatening consequences of infection. The first strategy focuses on the spreaders of infection and therefore on reducing the basic reproductive number or R0, the second on protecting the groups with the highest risk of morbidity and mortality. Most lessons are learned from the epidemic in Wuhan, China. Studying 25,961 laboratory confirmed COVID 19 cases with a median age of 57 years, Wang and coworkers [2] calculated that the R0 dropped from 3.86 before interventions to 0.32 post interventions in 18 days. The strict control measures involved control of the source of infection, cut off transmission routes and protection of vulnerable populations. Mathematical modeling by Prem et al. [3] indicated that the physical distancing measures were most effective if the return to work was staggered and initiated in early April, more than 2 months after the measures in Wuhan were fully implemented. The modeling also indicated that premature and abrupt lifting of interventions led to an early secondary wave of infections. However, the authors concluded that their analysis was limited by uncertainties around estimates of R0 and the duration of infectiousness. Gradual lifting of social distancing measures was initiated in Wuhan in early April. The American Enterprise Institute (AEI) released a report on March 28, 2020 entitled "National Coronavirus Response, A road Map to Reopening" [4] that defined triggers to move from the full implementation of social distancing measures to normalization of people's life. All is targeted towards postponing the second wave and ameliorating the severity of cases requiring hospitalization and intensive care treatment. According to the AEI report the trigger to move from the full restrictive fase to the fase of lifting restrictions is "at least 14 days of sustained reduction in cases (the down slope of the epidemic curve) and hospitals are able to treat all patients without resorting to crisis standard of care, and the capacity to test for virus in the nose and throat of all people with COVID 19 symptoms as well as the ability to actively monitor active cases and contacts. At that point the majority of schools, universities and businesses can gradually reopen, the report suggests. Contact tracing from then on is key. Working from home and enhanced hygiene measures should stay in place including limiting gatherings of more than 50 people for the whole population in this fase and all physical distancing measures should stay in place in full for the most vulnerable, the people over 60 years of age Jaap Goudsmit jgoudsmit@hsph.harvard.edu
European Journal of Epidemiology