Dear Editor,
We would like to thank Drs El-Saed and Alshamrani for their helpful questions concerning our paper (Gholami et al., 2021). The purpose of this paper was to extract data for meta-analysis from all comprehensive studies reporting characteristics and outcomes of healthcare workers (HCW) with PCR-proven Covid-19 infection. We included the N (total population) of HCW in all the tables only if actual data concerning this population was provided in the publication. Our requirement for this data was that it be collected by some form of actual survey or testing and not from secondary sources. We did not include data that merely represented an estimate, was a secondary source or had unclear methodology. We were consistent throughout the study to use these criteria. We acknowledge that a limitation of this analysis is that some of the included papers lacked accurate data related to the denominator, resulting in overestimating the result as it relates to an entire population of HCW. Furthermore, we would like to emphasize that the final estimates of percentages and confidence intervals reported in meta-analyses result from estimates of the individual weight of a given study, which is derived from the measures of study size and homogeneity and does not reflect a simple input of the total numbers from all studies into the numerator and the denominator.
In terms of the proportion of HCW that were Covid-19 positive, we reported the overall percentage of Covid-19 positive HCW in all published studies of HCW that met our search criteria, which included some studies that only contained 100% Covid-19 positive HCW in their reports. As mentioned by Drs El-Saed and Alshamrani, the paper of Zheng et al. reported comprehensive data related to 2457 Covid-19 positive HCW from Wuhan, China. This paper did mention that in Wuhan there are estimated to be 117,100 HCW, but this data did not meet our inclusion criteria and was not entered (Zheng et al., 2020). Similarly, we included the data from the US Covid Response Team of 8495 HCW with Covid-19 identified in all the reports received of Covid-19 positive patients in the entire United States (CDC COVID-19 Response Team et al., 2020). This study did not include any data related to the overall population of HCW in the United States (CDC COVID-19 Response Team et al., 2020). For a sensitivity analysis, if we exclude all the data from these two studies and repeat our analysis, then the percentage of Covid-19 positive HCW in the remaining included studies is 45.5% with 95%CI (29.3,62.8). Finally, if we totally exclude all reports that lacked data related to the entire HCW population from which the sample came, we are left with 17 studies with the percentage Covid-19 positive HCW of 12.5% with 95%CI (6.2,23.5). Note that the most accurate or “true” prevalence of Covid-19 among HCW can only come from proper epidemiological studies with rigorous methodologies or meta-analyses specific to analyzing prevalence in entire populations using different criteria and assumptions.
In terms of hospitalization and mortality rates, we used the same criteria for including data related to the N (total population) of HCW within a given study. Some studies did not include any data at all or any data meeting our criteria for this type of denominator. For example, from Zhan et al., we only included the data on 23 deaths that were reported in the publication. It was stated that these occurred from a total estimated population of 3387 HCW with COVID-19 infection in all of China. Since this was from a secondary source with unclear methodology, it was not included (Zhan et al., 2020). For a sensitivity analysis, if we exclude this paper from our analysis, the mortality rate is 0.8% with 95%CI (0.4,1.6), which is within the CI of our original estimate. In terms of hospitalization, if we exclude the studies that did not include data for a denominator for the total population (five studies from China: Chu et al., 2020, Wei et al., 2020, Xing et al., 2020, Zhan et al., 2020, Wang et al., 2020), then the hospitalization estimate is reduced to 4.7% with 95%CI (0.8,10.4). Note the wide CI that overlaps the CI of our original estimate, but these revised data may be more indicative of these rates when considering overall populations.
We do agree with Drs Al Saed and Alshanrani that future reviews and meta-analyses on COVID-19 morbidity and mortality among HCW should differentiate between studies using PCR and antibody testing in confirming cases and that estimates of symptomatic vs. asymptomatic infections are important. Thank you again for the opportunity to make these clarifications.
Conflict of interest
None declare.
Funding source
None declare.
Ethical approval
Approval was not required for this study.
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