Since the beginning of the SARS-CoV-2 pandemic, health care workers (HCWs) have been valiantly performing their critical duties in spite of being very exposed to infection. Not only their ranks have been decimated by a surge of infections and deaths, but they also have contributed to the dire spread of the virus in their own communities. The possibility of a second wave of the infection has alerted the Public Health authorities to the need to properly determine the incidence of infection in their rank and file.

In the United Kingdom, the rate of infection in London is double than the rest of the country, which prodded several institutions to pool their human and material resources to conduct a prospective cohort study of HCWs between March 26 and April 8, 2020 in several city institutions. Clinical cohort studies can either be:

  1. Prospective: a group of participants is selected and then studied forward to find out if there are any changes from the baseline data.
  2. Retrospective: a group of participants is selected, and their past data is studied to find any meaningful features.

For this prospective cohort  they recruited 200 patient-facing HCWs from a National Health Service (NHS) hospital trust in London; they collected nasopharyngeal swabs for RT-PCR twice per week, symptom data, and blood samples monthly for high-sensitivity serology assays (ELISA and flow cytometry for spike glycoprotein) The median age of the participants was 34 years old. They found that 44% (87) of the HCWs had evidence of infection at any moment during the study. Based on the serological results, 45% (82) were seropositive one month after the starting date, 20% (36) seroconverted during the study period, 25% (46) were already positive at the study’s start and 21% (42) tested positive in at least one nasopharyngeal swab.

They also found a trend towards a higher infection rate in younger participants than in the older ones; 31 out of 56 persons younger than 30 years got infected, while only 10 out of 30 persons older than 50 years old actually did. There was a significant number of asymptomatic carriers as 38% of the 42 positive HCWs did not report any meaningful symptomatology within 7 days of testing positive for SARS-CoV-2. The median age of onset of symptoms for those that were positive RT-PCR until they reported symptoms was 4 days; none of the participants had to be hospitalized.

The researchers said: “Notwithstanding the short follow-up period, these results suggest a protective effect, correlating with the presence of spike protein-specific antibodies, on subsequent infection within a 1-month period in a high risk setting.”

The featured photo was taken from: By University of Liverpool Faculty of Health & Life Sciences from Liverpool, United Kingdom – Anenurin Bevan, Minister of Health, on the first day of the National Health Service, 5 July 1948 at Park Hospital, Davyhulme, near Manchester, CC BY-SA 2.0,

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