RESUMO
Primary health care providers (PHCPs), especially general practitioners (GPs) are essential to organise health care efficiently. During the COVID-19 pandemic, they also keep the pressure off hospitals. PHCPs are assumed to be at high risk of a COVID-19 infection, as they are exposed to a large portion of the population (usually with less personal protective equipment than other frontline health care workers(HCWs)). Nevertheless, previous seroprevalence studies focussed on the general population or HCWs in hospital settings, rather than PHCPs. The aim of this study was to determine the seroprevalence of PHCPs after the first and during the second SARS-CoV-2 wave in Flanders (Belgium) and compare it to the seroprevalence in the general population (blood donors). A prospective cohort of PHCPs, mainly GPs (n=698) was screened for IgG antibodies against SARS-CoV-2 at five different time-points (June-December 2020). The dried blood spots they produced were analysed using a Luminex multiplex immunoassay. The seroprevalence of PHCPs remained stable between June and September 2020 (4.6-5.0%), but increased significantly from October to December (8.1-13.4%) 2020. The seroprevalence of PHCPs was not significantly higher than the seroprevalence of the blood donors at the end of December 2020. In conclusion, the sharp increase in seroprevalence during the second COVID-19 wave in Flanders shows that PHCPs were more at risk during the second wave compared to the first one. However, the increase was in line with the general population suggesting that PHCPs mainly got infected in their private settings.
RESUMO
High-throughput serological tests that can detect neutralizing antibodies against SARS-CoV-2 are desirable for serosurveillance and vaccine efficacy evaluation. Although the conventional neutralization test (cVNT) remains the gold standard to confirm the presence of neutralizing antibodies in sera, the test is too labour-intensive for massive screening programs and less reproducible as live virus and cell culture is involved. Here, we performed an independent evaluation of a commercially available surrogate virus neutralization test (sVNT, GenScript cPass) that can be done without biosafety level 3 containment in less than 2 hours. When using the cVNT and a Luminex multiplex immunoassay (MIA) as reference, the sVNT obtained a sensitivity of 94% (CI 90-96%) on a panel of 317 immune sera that were obtained from hospitalized and mild COVID-19 cases from Belgium and a sensitivity of 89% (CI 81-93%) on a panel of 184 healthcare workers from the Democratic Republic of Congo. We also found strong antibody titer correlations (rs>0.8) among the different techniques used. In conclusion, our evaluation suggests that the sVNT could be a powerful tool to monitor/detect neutralising antibodies in cohort and population studies. The technique could be especially useful for vaccine evaluation studies in sub-Saharan Africa where the basic infrastructure to perform cVNTs is lacking.
