SARS-CoV-2 Antibody Prevalence Among 85,529 Healthcare Workers Following the First Wave of COVID-19 in Chile (preprint)

Background: Healthcare workers (HCWs) are at increased risk for SARS-CoV-2 infection, however not all face the same risk. We aimed to determine antibody prevalence and risk factors associated with seropositivity in the Chilean HCW community.Methods: This was a nationwide, cross-sectional study consisting of a questionnaire and COVID-19 antibody testing. All HCWs in the Chilean public health care system were invited to participate three to four months following the peak of the country's first wave.Findings: Overall SARS-Cov-2 blood antibody positivity by fingerstick or venipuncture in 85 529 HCWs was 7 · 2%, ranging from 1 · 6% to 12 · 4% between regions. SARS-Cov-2 positive PCR results were self-reported in 8 330 individuals (9 · 7%) of which 47% were seropositive. Overall 10 863 (12 · 7%) either reported prior PCR positive results and/or were seropositive. Several factors were independently associated with higher IRR for seropositivity, including working in hospital (IRR 1·484), medicine/surgery w ards (IRR 1·383), emergency room (IRR 1·266), and night shifts (IRR 1·616), as were history of contact with a confirmed case (IRR 1·462), and use of public transport (IRR 1·367). These variables remained significant when including self-reported PCR positive cases in the model.Interpretation: HCWs in the hospital were at highest risk for COVID-19, especially if working in medicine/surgery wards or emergency rooms, in night shifts, older age, exposed to confirmed cases and/or using public transport. Antibody results using lateral flow likely underestimated true infection rates by nearly 40-50%. Nevertheless, risk factors were sustained when adjusting for self-reported PCR positive cases.Funding: No funding institution.Conflict of Interest: Authors do not declare any conflict of interest.Ethical Approval: The study was designed in August 2020 by Health Ministry personnel in conjunction with an academicadvisory board; the study was approved by the Ethical Committee of the Servicio de Salud Araucanía Sur (Nº CEC-201, August 10, 2021).

Optimizing RT-PCR detection of SARS-CoV-2 for developing countries using pool testing (preprint)

The global shortage of reagents and kits for nucleic acid extraction and molecular detection of SARS-CoV-2, requires new cost-effective strategies for the diagnosis of suspected COVID-19 cases, especially in countries that need to increase detection capacity. Pooled nucleic acid testing has been extensively used as a cost-effective strategy for HIV, HepB, HepC and influenza. Also, protocols dispensing of RNA extraction appears as an attractive option for detection of SARS-CoV-2. In this study, pooling nasopharyngeal samples with both automated and manual extraction proved reliable, and thus a potential efficient alternative for the diagnosis of suspected COVID-19 in developing countries.