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Hospital clinicians taking care of the sickest COVID-19 patients were associated with the lowest risk of seropositivity versus those working in other areas of the hospital, and personal protective equipment (PPE) may have played a role, British researchers found.

After adjustment, working in intensive care medicine was associated with a reduced risk of COVID-19 seropositivity (adjusted OR 0.28, 95% CI 0.09-0.78, P=0.02), reported Alex Richter, MD, of the University of Birmingham in England, and colleagues.

However, those in general internal medicine, acute medicine, and housekeeping services had a higher risk of seropositivity, they wrote in .

They hypothesized varying levels of PPE played a role, as intensive care clinicians and those in designated "high risk areas" of the hospital had access to "enhanced PPE," including "filtered face piece (class 3)" respirators. FFP3 respirators are said to filter out at least 99% of airborne particles. Surgical masks were recommended for staff in other clinical areas.

"We presumed that intensive care workers were going to have the highest risk," Richter said in a podcast about the study. "Something like the PPE and the protective equipment the individuals were wearing may well play an important part in this finding."

But she noted the study was not specifically set up to examine PPE, adding further research is needed to determine if the type of PPE plays a role in infection risk. Some American physicians encouraged N95 masks for all inpatient care during the COVID-19 pandemic, though many organizations say surgical masks are adequate for most healthcare providers.

Richter and colleagues checked 545 asymptomatic healthcare personnel at the National Health Services' Birmingham hospital system on April 24-25. Mean age was 42, 75% were women, and about half were "white British." They were tested for COVID-19 via a nasopharyngeal swab to detect SARS-CoV-2 RNA and a blood sample to detect anti-SARS-CoV-2 spike glycoprotein antibodies.

Overall, 2.4% tested positive for SARS-CoV-2 RNA. Of these, 15% also had antibodies in their serum and 39% subsequently developed symptoms of COVID-19. Of 516 individuals with serum available, 24.4% had detectable antibodies.

Seropositivity was highest among housekeeping (35%), followed by acute medicine (33%) and general internal medicine (30.3%), followed by intensive care (15%), emergency medicine and general surgery (13% apiece). However, these were based on small numbers -- ranging from 15 workers in emergency medicine up to 61 in intensive care.

Examining demographics, there was no significant difference in seroprevalence between women and men in univariate or multivariate analyses. However, individuals of Black, Asian, and minority ethnic descent were at significantly greater risk of seropositivity than white individuals.

Limitations to the data include self-selection by participants, which could bias the results, and that data were not available to determine how representative the sample was in individual groups "with the total number of staff at work on the day of the study."

Richter said these factors are important, especially as hospitals look ahead to the arrival of influenza season, against the backdrop of COVID-19.

"If there is [another surge], how do we protect our healthcare workers this winter," she said.

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