We assessed the prevalence of COVID-19 antibodies among the frontline HCWs and explored the association between the occupational risks imposed by the patient contact with the presence of COVID-19 antibodies. In the early stages of the pandemic, various countries that conducted assessments of the true COVID-19 infection rate among HCWs reported varying levels of prevalence that ranged from 1.26% of seropositivity in Greece to 24.4% in the United Kingdom. Our study found a comparable level of COVID-19 antibody prevalence among HCWs (15.0%) with studies from England and China (17.97% and 17.14%, respectively).[14],[5] Authors proposed various explanations to the quite diverging prevalence reports, such as variations in the study designs and assessment methods, effective use of PPE, proper adherence to infection prevention and control measures as well as overall low infection rate in the hospital settings and in the community. The possible reasons for the relatively high prevalence of COVID-19 antibodies in Armenian HCWs could be the suboptimal use of PPE, and widespread community transmission during the first wave of the epidemic in the country.
In contrast to our report, several studies demonstrated low seroprevalence among HCWs, which was explained by the low regional prevalence of infection.[15],[16],[17] Thus, the low seroprevalence among HCWs in Greece was connected with the low overall seroprevalence (1.26% and 0.12%).[15] In Italy the seroprevalence among HCW was 3.4% which might be related to the high infectious rate.[16]
The analysis of risk factors of COVID-19 antibodies showed that primary work location was the only predictor of COVID-19 antibodies in the general pool of HCWs. This finding was consistent with Mascola J. et al. and Vivier E. et al., reported similar results. [21],[22] Our study also showed that the ICU HCWs had the highest seroprevalence (27.4%) and the highest odds of having COVID-19 antibodies compared to the hospital and PHC HCWs. Several international studies found a significantly higher probability of antibodies among HCWs from high—risk departments.[18],[19] Wax et al. explained this phenomenon by the higher risk of aerosol generation imposed by the procedures for the provision of respiratory support.[20] Unlike these findings, more studies reported lower seroprevalence among ICU workers explained by the enhanced use of PPE in a high-risk environment.[23],[24] Another explanation proposed by Shields A. et al. and Galanis P. et al. was the fact that patients are usually admitted to the ICU around the 10th day of the illness when the viral load is already decreasing.[23],[6]
In addition, we identified variations of seroprevalence of SARS-CoV-2 antibodies among different professional groups of health care workers. A relatively low prevalence of antibodies among administrative staff and employees of hospitals was in line with some studies and might be explained by low direct contact with patients.[19, 25] The highest prevalence of antibodies was among hospital physicians and nurses at 20.4%. This finding is consistent with various studies that revealed an elevated risk of COVID-19 antibodies among clinical staff immediately involved in COVID-19 patient care.[26],[27],[28] Barocco et al., demonstrated similar patterns of high antibodies prevalence among nurses and other medical staff (17.95% and 17.03%, respectively).[29] Similarly, Rudberg et al. reported high seroprevalence among assisting nurses (25.47%), nurses (21.86%), and physicians (19.13%).[19] However, in our study the stratified analysis of additional risk factors of the presence of COVID-19 antibodies within the work locations did not show that being from a certain professional group was associated with increased risk of COVID-19 antibody prevalence. The small sample size could have affected the ability to detect a significant difference.
All the discussed factors that showed a significant influence on having COVID-19 antibodies are linked to direct COVID-19 patient care. The finding of the stratified analysis within the hospital setting showing that close contacts with COVID-19 patients were significantly associated with having COVID-19 antibodies, is in line with numerous similar studies.[5],[30] The latter could be explained by direct communications with patients or sharing conversations within close distance with them which can increase the probability of being infected. This finding emphasizes the implementation, use, and importance of PPE, especially within hospitals. The reason for the absence of statistical significance between having close contacts and COVID-19 antibodies in the analysis within the PHC facilities could be the fact that the patient-provider relationship within the PHC facilities does not assume a direct patient contact similar to the hospital setting. In contrast, in the ICUs the fact that all HCWs are involved in direct patient care assuming a high level of patient contact, the absence of a comparison group could be the reason for non-significant findings. Lastly, a higher prevalence of COVID-19 antibodies among those study participants who did not report past PCR-confirmed COVID-19 diagnosis indicates the high prevalence of undetected COVID-19 infection in the studied healthcare facilities. Various studies also find similar patterns of COVID-19 transmission among HCWs, highlighting the importance of early detection or screening programs for HCWs to decrease in-hospital transmission as well as the role of proper PPE usage.[31],[21],[18],[32],[19]