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Tamiflu lowers odds of secondary H3N2 infection in LTCF outbreaks

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June 25, 2018

In one Canadian province, for every day that passed from the start of an influenza A (H3N2) outbreak in long-term care facilities to the initiation of Tamiflu, the odds of an at-risk resident developing symptomatic infection increased by 33%, according to findings published in Infection Control & Hospital Epidemiology.

In a retrospective cohort study, Davinder Singh, MD, of the department of community health sciences at the University of Manitoba, and colleagues assessed patient treatment and outcomes in 94 outbreaks of H3N2 in long-term care facilities (LTCFs) that occurred between October 2014 and May 2015 in Manitoba.

Similar to Infectious Diseases Society of America recommendations, when outbreaks of influenza are detected in LTCFs in Manitoba, it is standard protocol to treat symptomatic patients with 5 days of oral Tamiflu (oseltamivir, Genentech) and give all other residents 10 days of preventive oseltamivir, according to Singh and colleagues.

H3N2, the main driver of the recent severe influenza season in the United States, is notoriously difficult to prevent, prone to mutation and causes relatively severe illness.

The analysis by Singh and colleagues included 53 outbreaks involving 5,258 residents. The average secondary attack rate was between 14% and 24%, and there was an average of 3.85 days from the second case to oseltamivir chemoprophylaxis.

According to their findings, delaying oseltamivir chemoprophylaxis was associated with increased odds of infection, with an adjusted OR of 1.3 (95% CI, 1.2-1.5) per day for H3N2.

“This study provides strong evidence supporting the rapid detection of influenza A H3N2 outbreaks and the rapid administration of oseltamivir chemoprophylaxis in a [long-term care] resident population,” Singh and colleagues wrote. “Delays in this process can occur at many key points, including collection of nasopharyngeal specimens, transport of specimens to the laboratory, identification of viruses present, communication of results, making the decision to administer oseltamivir chemoprophylaxis, and the actual administration of oseltamivir.” – by Jennifer Byrne

Disclosure: The researchers report no relevant disclosures.

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