RESUMO
The prevalence and longevity of acquired immunity to coronavirus disease 2019 (COVID-19) in health care workers (HCWs) is of great interest, especially with the roll-out of vaccines for SARS-CoV-2. Determining such immunity may enhance knowledge about susceptibility of HCWs to COVID-19, frequency of vaccine administration, and degree of workplace risk, and may also support enactment of better workplace policies and procedures. The present study reports on 6-months follow-up serosurveillance to determine the longevity of SARS-CoV-2 antibodies in HCWs. Sub-sample (n=35) of the original serosurveillance in HCWs (n = 3,458) with baseline, 8-week, and 6-month blood sampling were analyzed. Information on job duties, location, COVID-19 symptoms, polymerase chain reaction test history, travel since January 2020, and household contacts with COVID-19 was collected. Of 35 subjects, 13 were seropositive at baseline and maintained positivity at 8-week follow-up, with 3 losing positivity at 6-month follow-up. Among 22 subjects who were seronegative at baseline and seropositive at 8-week follow-up, all but one maintained positivity at 6-month follow-up. There was no significant effect of all factors (e.g., age, gender, job duties) examined at the .05 level on seropositivity at 6-month follow-up. The observed antibody longevity was 7.0+/-0.6 months for seropositive subjects (n=13), and 4.5+/-0.8 months for those seronegative subjects (n=22), at baseline. The longest duration of seropositivity observed in this cohort was 7.9 months (236 days). With reported COVID-19-related symptoms up to 4.7 months prior to baseline blood sampling, possibly longer antibody presence is suggested. Similarly, seropositivity at 6-month follow-up further suggests greater antibody longevity than observed in this study.
RESUMO
Understanding SARS-CoV-2 antibody prevalence as a marker of prior infection in a spectrum of healthcare workers (HCWs) may guide risk stratification and enactment of better health policies and procedures. The present study reported on cross-sectional study to determine the prevalence and longevity of SARS-CoV-2 antibodies in HCWs at a regional hospital system in Orange County, California, between May and August, 2020. Data from HCWs (n=3,458) were included in the analysis. Data from first responders (n=226) were also analyzed for comparison. A blood sample was collected at study enrollment and 8-week follow-up. Information on job duties, location, COVID-19 symptoms, polymerase chain reaction test history, travel since January 2020, and household contacts with COVID-19 was collected. Comparisons to estimated community prevalence were also evaluated. Observed antibody prevalence was 0.93% and 2.58% at initial and 8-week follow-up, respectively, for HCWs, and 5.31% and 4.35% for first responders. For HCWs, significant differences (p < .05) between negative vs. positive at initial assessment were found for age, race, fever, and loss of smell, and at 8-week follow-up for age, race, and all symptoms. Antibody positivity persisted at least 8 weeks in this cohort. Among 75 HCWs with self-reported prior PCR-confirmed COVID-19, 35 (46.7%) were antibody negative. Significant differences between negative vs. positive were observed in age and frequency of symptoms. This study found considerably lower SARS-CoV-2 antibody prevalence among HCWs compared with prior published studies. This may be explained by better safety measures in the workplace, heightened awareness inside and outside of the workplace, possibly lower susceptibility due to innate immunity and other biological heterogeneity, and low COVID-19 prevalence in the community itself. HCWs with initial positive results had persistent positive serologies at 8 weeks. Further research is warranted to investigate factors influencing such lower prevalence in our HCWs.
RESUMO
SARS-CoV-2 has driven a pandemic crisis. Serological surveys have been conducted to establish prevalence for covid-19 antibody in various cohorts and communities. However, the prevalence among healthcare workers is still being analyzed. The present study reports on initial sero-surveillance conducted on healthcare workers at a regional hospital system in Orange County, California, during May and June, 2020. Study participants were recruited from the entire hospital employee workforce and the independent medical staff. Data were collected for job title, location, covid-19 symptoms, a PCR test history, travel record since January 2020, and existence of household contacts with covid-19. A blood sample was collected from each subject for serum analysis for IgG antibodies to SARS- CoV-2. Of 3,013 tested individuals, a total 2,932 were included in the analysis due to some missing data. Observed prevalence of 1.06% (31 antibody positive cases), adjusted prevalence of 1.13% for test sensitivity and specificity were identified. Significant group differences between positive vs. negative were observed for age (z = 2.65, p = .008), race (p = .037), presence of fever (p < .001) and loss of smell (p < .001). Possible explanation for this low prevalence includes a relatively low local geographic community prevalence ([~]4.4%) at the time of testing, the hospitals timely procurement of personal protective equipment, rigorous employee education, patient triage and treatment protocol development and implementation. In addition, possible greater presence of cross- reactive adaptive T cell mediated immunity in healthcare workers vs. the general population may have contributed. Determining antibody prevalence in front-line workers, and duration of antibody presence may help stratify the workforce for risk, establish better health place policies and procedures, and potentially better mitigate transmission.
