Comparison of risk factors for SARS-CoV-2 infection among healthcare workers during Omicron and Delta dominance periods in Japan.

BACKGROUND: The risk factors for coronavirus disease (COVID-19) among healthcare workers (HCWs) might have changed since the emergence of the highly immune evasive Omicron variant. AIM: To compare the risk factors for severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) infection among HCWs during the Delta- and Omicron-predominant periods. METHODS: Using data from repeated serosurveys among the staff of a medical research centre in Tokyo, two cohorts were established: Delta period cohort (N = 858) and Omicron period cohort (N = 652). The potential risk factors were assessed using a questionnaire. Acute/current or past SARS-CoV-2 infection was identified by polymerase chain reaction or anti-nucleocapsid antibody tests, respectively. Poisson regression was used to calculate the risk ratio (RR) of infection risk. FINDINGS: The risk of SARS-CoV-2 infection during the early Omicron-predominant period was 3.4-fold higher than during the Delta-predominant period. Neither working in a COVID-19-related department nor having a higher degree of occupational exposure to SARS-CoV-2 was associated with an increased infection risk during both periods. During the Omicron-predominant period, infection risk was higher among those who spent ≥30 min in closed spaces, crowded spaces, and close-contact settings without wearing mask (≥3 times versus never: RR: 6.62; 95% confidence interval: 3.01-14.58), whereas no such association was found during the Delta period. CONCLUSION: Occupational exposure to COVID-19-related work was not associated with the risk of SARS-CoV-2 infection in the Delta or Omicron period, whereas high-risk behaviours were associated with an increased infection risk during the Omicron period.

A hemodialysis patient who escaped aggravation of COVID-19 after SARS-CoV-2 infection

Dialysis patients are compromised hosts;thus, they might become even more seriously ill in the case of infection with severe acute respiratory syndrome coronavirus 2 (SARS-COV-2). A man in his 50s under maintenance dialysis was accidentally a close contact of someone with SARS-COV-2 infection. Therefore, he received the PCR test for SARS-COV-2 three days a week at the time of his visit to our hospital for his hemodialysis session. He was admitted the day after the result of the PCR test was positive. This patient belongs to a high-risk group with severe illnesses, including the fact that he had not been vaccinated against SARS-COV-2. He received antibody cocktail therapy (casirivimab/imdevimab) on the day he was hospitalized. As a result, he escaped aggravation of COVID-19. This case suggests the important of early diagnosis and early treatment with this cocktail therapy for prevention of aggravation of COVID19 in high-risk hemodialysis patients.