Nosocomial COVID-19 infection, even with omicron variant, increased mortality
Patients who caught SARS-CoV-2 in the hospital early in the pandemic had double the risk of death during hospitalization as matched inpatient controls without COVID-19; those who caught later variants had a lower, but still significant, increase in risk of inpatient mortality.
Catching COVID-19 in the hospital was associated with longer length of stay and higher mortality risk, according to a new study.
The retrospective study included patients treated at five hospitals in Massachusetts in December 2020 to April 2023. Patients who tested negative for SARS-CoV-2 at admission and on hospital day 3 but tested positive on or after hospital day 5 were matched to uninfected controls by hospital, service, time period, days since admission, and propensity scores that incorporated demographics, comorbidities, vaccination status, primary diagnosis, vital signs, and lab values. Results were published by Annals of Internal Medicine on July 16.
The study included 274 cases of hospital-onset SARS-CoV-2 infection from before the omicron variant became dominant and 1,037 from the omicron period (0.17 vs. 0.49 cases per 100 admissions). Patients who acquired COVID-19 in the hospital were older and had more comorbid conditions than those who did not. In the pre-omicron period, infection was associated with ICU admission, need for high-flow oxygen, length of stay, and mortality (risk ratio [RR], 2.0; 95% CI, 1.1 to 3.8) versus controls. These associations continued during the omicron period, although the risk of mortality was attenuated (RR, 1.6; 95% CI, 1.2 to 2.3).
"Of note, this study was done during a period when many measures to prevent transmission were in place," said the study authors. "Possible reasons for the persistence of hospital-onset infections despite these measures include staff working despite being ill, visitors seeing patients despite being ill, lapses in masking, inadequate ventilation in some locations, and the limited effectiveness of surgical masks for both source control and exposure control."
They listed some strategies to reduce transmission, suggesting that these be considered especially when community rates of COVID-19 are high: "enacting stronger policies to discourage staff from working when ill (such as more flexible sick policies), actively screening visitors to stop symptomatic persons from visiting, mandating SARS-CoV-2 vaccines for health care workers, improving ventilation, decreasing or eliminating shared rooms, adding air cleaners, encouraging more consistent masking, and using respirators rather than surgical masks."
