Nursing and healthcare-associated pneumonia due to SARS-CoV-2 Omicron variant.

Background: There were many differences in the clinical characteristics between nursing and healthcare-associated pneumonia (NHCAP) and community-acquired pneumonia (CAP) due to the SARS-CoV-2 ancestral strain, Alpha variant and Delta variant. With the replacement of the Delta variant by the Omicron variant, the Omicron variant showed decreased infectivity to lung and was less pathogenic. We investigated the clinical differences between NHCAP and CAP due to the Omicron variant.

Methods: We analyzed 516 NHCAP and 547 CAP patients with COVID-19 pneumonia. Of 516 patients with COVID-19 NHCAP, 330 cases were the Omicron variant (120 cases were BA.1, 53 cases were BA.2, and 157 cases were BA.5 subvariants) and 186 cases were non-Omicron variants.

Results: The median age, frequency of comorbid illness, rates of intensive care unit (ICU) stay, and mortality rate were significantly higher in Omicron patients with NHCAP than in those with CAP. Rates of ICU stay and in-hospital mortality were significantly higher in NHCAP patients with non-Omicron variants compared with those in the Omicron variant group. No clinical differences were observed in patients with NHCAP among the Omicron BA.1, BA.2, and BA.5 subvariant groups.

Conclusions: The present study supported that the NHCAP category is necessary not only for bacterial pneumonia but also viral pneumonia. It is necessary to consider prevention and treatment strategies depending on the presence or absence of applicable criteria for NHCAP.