During the COVID-19 pandemic, infection of farmed mink has become not only an economic issue but also a widespread public health concern. International agencies have advised the use of strict molecular and serosurveillance methods for monitoring the SARS-CoV2 status on mink farms. We developed 2 ELISAs and a duplex protein microarray immunoassay (MI), all in a double-recognition format (DR), to detect SARS-CoV2 antibodies specific to the receptor-binding domain (RBD) of the spike protein and to the full-length nucleoprotein (N) in mink sera. We collected 264 mink serum samples and 126 oropharyngeal samples from 5 Spanish mink farms. In both of the ELISAs and the MI, RBD performed better than N protein for serologic differentiation of mink from SARS-CoV2–positive and –negative farms. Therefore, RBD was the optimal antigenic target for serosurveillance of mink farms.

Massive vaccination programs are being carried out to limit the SARS-CoV-2 pandemic that started in December 2019. Serological tests are of major importance as an indicator of circulation of the virus and to assess how vaccine-induced immunity progresses. An Enzyme-Linked Immunosorbent Assay (ELISA) and a Lateral Flow Assay (LFA) have been developed based on the SARS-CoV-2 recombinant Receptor Binding Domain (RBD) and the combination of Spike and Nucleoprotein, respectively. The validation with 1272 serum samples by comparison with INgezim® COVID 19 DR showed good diagnostic performance (sensitivity: 93.2%-97.2%; specificity: 98.3%-99.3%) for detection of previous contact with SARS-CoV-2. Moreover, according to our results, these assays can help in the serosurveillance during and after vaccination, by detecting the humoral immune response as soon as 15 days post-vaccination and identifying low-respondents. Hence, these tests could play a key role in the progression to a COVID-19 free world, helping to adjust future vaccination protocols.