Antibody response to first and second dose of BNT162b2 in a cohort of characterized healthcare workers (preprint)

BackgroundVaccine-induced population immunity is a key global strategy to control coronavirus disease 2019 (COVID-19). The rapid implementation and availability of several COVID-19 vaccines is now a global health-care priority but more information about humoral responses to single- and double-dose vaccine is needed Methods163 health care workers (HCW) of the Padua University Hospitals, who underwent a complete vaccination campaign with BNT162b2 vaccine were asked to collect serum samples at 12 (t12) and 28 (t28) days after the first inoculum to allow the measurement of SARS-CoV-2 Antibodies (Ab) using chemiluminescent assays against the spike (S) protein and the Receptor Binding Domain (RBD) of the virus, respectively. ResultsSignificant differences were found at t12 for infection-naive and subjects with previous-natural infection who present higher values of specific antibodies, while no significant differences have been found between t12 and t28. No statistically significant difference was found between male and female, while lower Ab levels have been observed in subjects older than 60 years at t12 but not at t28. ConclusionsOur study confirms observed differences in vaccine responses between infection-naive and subjects with previous natural infection at t12 but not for a longer time. The influence of sex and age deserves further studies, even if the relationship with age seems particularly significant.

A longitudinal study of healthcare workers' surveillance during the ongoing COVID-19 Epidemics in Italy: is SARS-CoV-2 still a threat for the Health-care System? (preprint)

Objectives: In spring 2020, Northern Italy was the first area outside China to be involved in the SARS-CoV-2 pandemic. This observational study depicts SARS-CoV-2 prevalence and serological curves among first-line healthcare workers (HCWs) at Padua University Hospital (PdUH), North-East Italy. Method: 344 HCWs, working at the PdUH Emergency Department and Infectious Disease Unit, underwent a SARS-CoV-2 RNA nasopharyngeal swab with paired IgM and IgG antibody detection for 4 consecutive weeks. At every session, a questionnaire recorded symptoms, signs and recent contacts with SARS-CoV-2 patients. Positive cases were followed up for 5 months. Results: Twenty-seven HCWs (7.84%) had positive serology (Abs) with 12 positive swabs during the study period. Two additional HCWs were positive by swab but without Abs. Fourteen cases (4%) had SARS-CoV-2 infection before the beginning of the study. An HCW with autoimmune disease showed false Ab results. 46% of individuals with Abs reported no symptoms, in accordance with previous population studies. Fever, nasal congestion, diarrhoea and contacts with SARS-CoV-2 individuals correlated to SARS-CoV-2 infection. 96% of Abs+ cases showed persistent positive antibodies 5 months later and none was re-infected. Discussion: Correct use of PPEs and separate paths for positive/negative patients in the hospital can result in a low percentage of SARS-CoV-2 infections among HCWs, even in high risk settings. Frequent testing for SARS-CoV-2 with nasopharyngeal swabs is worthwhile, irrespective of HCWs' symptoms, due to the lack of specificity together with the high percentage of asymptomatic cases. Further studies are needed to elucidate the neutralizing effect of SARS-CoV-2 antibodies.