Outbreaks of influenza-like illness in care homes in the East of England: impact of variations in neuraminidase inhibitor provision

Objectives: To examine the differences in outcomes related to variable provision of antivirals in care home respiratory outbreaks. Study design: This is a retrospective observational study. Methods: Routinely collected outbreak surveillance data reported from care home staff was recorded using a standard template and extracted from the Public Health England health protection electronic records. Data included numbers of people affected, provision of oseltamivir, hospitalization, and deaths during the outbreak in the care home. Oseltamivir provision was categorized by proportion of eligible residents prescribed it on advice. Additional data on microbiological diagnoses were obtained directly from the hospital laboratories. Logistic regression was used to examine associations between oseltamivir provision and hospitalizations and deaths in care homes. Results: One hundred and sixty-eight outbreaks were reported from 28th July 2016 until 27th March 2017, affecting 1459 residents and 347 staff. There were 76 hospital admissions and 37 deaths overall. Although deaths and hospital admissions also occurred in outbreaks caused by other respiratory viruses, outbreaks caused by influenza had the highest median number of people affected and a greater proportion of hospital admissions and deaths. Of the 56 outbreaks caused by influenza, there was a significant increase in the odds of the care home reporting deaths when oseltamivir was not used (odds ratio = 8.15, 95% confidence interval = 1.38–48.20, P = 0.02). There were also non-significant reductions in duration of outbreak and hospital admissions in care home outbreaks with oseltamivir treatment. Conclusions: Partial or no provision of oseltamivir was associated with poorer outcomes in laboratory-confirmed influenza outbreaks.