Hospital-Wide SARS-CoV-2 seroprevalence in health care workers in a Spanish teaching hospital

Impact of previous COVID-19 on immune response after a single dose of BNT162b2 SARS-CoV-2 vaccine

“…A random sample of 642 health-care workers (HCW) enrolled in a previous hospital-wide seroprevalence study of 2,590 HCW (April-2020 and November-2020; [7]) were invited to participate in this study, based on stratification of 3 groups according to their seropositive status in both surveys: 1) Naïve SARS-CoV-2 patients: Seronegative in both surveys; 2) Transient seropositivity: seropositive in first survey and negative in second survey and 3) Persistent seropositivity: seropositive in both surveys. Seropositive HCW were further classified according to the severity of the previous SARS-CoV-2 infection 1) asymptomatic; 2) moderate COVID-19, attended as out-patients; and 3) severe COVID-19: HCW that required hospital admission.…”

Risk of SARS-CoV-2 Infection in Previously Infected and Non-Infected Cohorts of Health Workers at High Risk of Exposure

“…Unfortunately, it has been scarcely evaluated in a cohort of participants highly exposed to the virus [ 10 ]. Healthcare workers in Spain were badly hit by the pandemic during the first wave with infection proportions ranging from 25.8% to 33.8% in a cross-sectional study performed in May 2020 [ 11 ]. Healthcare workers highly exposed to the SARS-CoV-2 represent an outstanding opportunity to study risk of reinfection.…”

SARS-CoV-2 new infections among health-care workers after the first dose of the BNT162b2 mRNA COVID-19 vaccine. A hospital-wide cohort study

“…By Poisson model regression analysis, the reduced incidence among HCW adjusting for the background changes in the general population remained statistically and clinically significant: 3% reduction (IRR 0.272; 95% CI 0.164-0.451 p<0.001) after the first dose of the vaccine and 92 % (IRR 0.176, 95% CI 0.033-0.174; p<0.001) after the second dose (Supplemental Tables and Figure). It is conceivable that the response to the vaccine among HCW may have been boosted by a previous exposure to the virus [ 12 , 13 ].. As a sensitive analysis we restricted the evaluation of new SARS.CoV-2 infections to HCW (n=1582) who had never tested positive in any of our wide seroprevalence surveys [ 7 ]. As shown in the supplementary table 2 , the decline in new SARS-CoV-2 infections was essentially identical to the total HCW population.…”

“…Our results after a single dose of the vaccine might not be extrapolated to other settings: our vaccination program was extended to all HCW, including HCW with previous SARS-COV-2 documented infection [ 7 ]. We and others have recently shown that HCW with a previous SARS-CoV-2 infection exhibit a strong serologic response to the first dose of the vaccine, reaching higher IgG anti spike titre than that obtained after full vaccination in SARS-CoV-2 naïve individuals [ 12 , 13 ].…”

“…If negative, a SARS-CoV-2 PCR test was performed 48-72 hours thereafter. Asymptomatic HCW were evaluated by SARS-CoV-2 PCR test in nasopharyngeal swabs with Bio-Rad CFX96™ Real-Time PCR Detection System, as previously described [ 7 , 8 ]. New HCW infections were defined as a SARS-CoV-2 positive antigen or PCR test.…”