Severe outcomes in residents of Long Term Care Facilities following infection with SARS-CoV-2 Omicron variant (VIVALDI study) (preprint)

ABSTRACT

Background Recently there has been a rapid, global increase in SARS-CoV-2 infections associated with the Omicron variant (B.1.1.529). Although severity of Omicron cases may be reduced, the scale of infection suggests hospital admissions and deaths may be substantial. Definitive conclusions about disease severity require evidence from populations with the greatest risk of severe outcomes, such as residents of Long-Term Care Facilities (LTCFs). Methods We used a cohort study to compare the risk of hospital admission or death in LTCF residents in England who had tested positive for SARS-CoV-2 in the period shortly before Omicron emerged (Delta dominant) and the Omicron-dominant period, adjusting for age, sex, vaccine type, and booster vaccination. Variants were confirmed by sequencing or spike-gene status in a subset. Results Risk of hospital admission was markedly lower in 398 residents infected in the pre-Omicron period (10.8% hospitalised, 95% CI 8.13-14.29) compared to 1241 residents infected in the Omicron-period (4.01% hospitalised, 95% CI 2.87-5.59, adjusted Hazard Ratio 0.50, 95% CI 0.29-0.87, p=0.014); findings were similar in residents with confirmed variant. No residents with previous infection were hospitalised in either period. Mortality was lower in the Omicron versus the pre-Omicron period, (p<0.0001). Conclusions Risk of severe outcomes in LTCF residents with the SARS-CoV-2 Omicron variant was substantially lower than that seen for previous variants. This suggests the current wave of Omicron infections is unlikely to lead to a major surge in severe disease in LTCF populations with high levels of vaccine coverage and/or natural immunity. Trial Registration Number ISRCTN 14447421