This article is written live from ID Week 2017 Annual Meeting in San Diego, CA. MPR will be reporting news on the latest findings from leading experts in infectious diseases. Check back for more news from IDWeek 2017.

SAN DIEGO—Inpatient administration of antivirals significantly reduces intensive care unit (ICU) admissions and the need for mechanical ventilation (MV) among hospitalized patients with influenza, a team of Canadian researchers reported at IDWeek 2017. 

The analysis “supports the use of antivirals to prevent serious influenza-related outcomes in hospitalized patients,” said coauthor Zach Shaffelburg, BSc, from the Canadian Center for Vaccinology, Halifax, NS, Canada. 

Antivirals appear to be effective at preventing ICU admission and mechanical ventilation regardless of when after symptom onset they are administered, but benefits were maximized with prompt initiation, the team found.

Despite the Canadian National Advisory Committee on Immunization’s recommendation that everybody aged 6 months or older be vaccinated annually against influenza unless a contraindication exists, vaccine coverage remains “suboptimal,” Shaffelburg noted. Similarly, despite CDC guidelines recommending prompt treatment with neuraminidase inhibitors for hospitalized patients with confirmed or suspected influenza, antiviral therapy rates in Canada have declined in recent years.

“It is estimated that influenza causes approximately 12,200 hospitalizations and 3,500 deaths in Canada each year,” he said. 

Improved clinical outcomes with antiviral treatment for influenza have previously been reported in outpatient settings but its impact in inpatient settings has not been as clear, so the research team investigated the impact of antiviral therapy on ICU admissions, the need for mechanical ventilation, and patient deaths within 30 days of discharge, among hospitalized patients with laboratory-confirmed influenza.

Using data from the Serious Outcomes Surveillance (SOS) Network of the Canadian Immunization Research Network (CIRN), the team included hospitalized patients with an acute respiratory illness from 2011 to 2014 who tested positive for influenza. 

The association between antiviral treatment and severe outcomes was stratified by time from symptom onset to treatment start: <48hr, 48hr–4 days, 5–21 days. A total of 4,861 patients were included across 3 flu seasons.   

Overall, 16% of patients were admitted to the ICU, 11% required MV and 9% died. 

The impact of the timing of antiviral use on ICU and MV risk did not reach statistical significance, with initiation <2 days, 2–4 days, or 5–21 days all exhibiting similar, substantial reductions in risk compared to that seen for patients who did not receive antivirals. (Odds ratios [ORs] compared to no-antivirals were 0.09, 0.09, and 0.11, respectively.) 

The OR for ICU or MV among patients who received antiviral use was 0.10 (95% CI: 0.08–0.14; P<001).  

The risks of ICU admission and/or MV in hospitalized patients with influenza A were also associated with pregnancy status (P=0.006), tobacco smoking status (P=0.018), and hospitalization during the 2013/2014 flu season (P=0.020).

Because of small sample sizes, it was not possible to estimate separate ORs for antiviral use and deaths among patients with influenza A and influenza B, and antiviral use was not statistically significantly protective against death among patients with any lab-confirmed influenzas (OR 0.9; 95% CI: 0.7–1.2; P=0.45, n.s.).

Approximately half of the hospitalized influenza patients (54%) were initiated on an antiviral.

“Treatment with antivirals was associated with a significant reduction in admission to ICU and/or need for MV (odds ratio [OR] 1.10, 95% CI: 0.08–0.13; P<0.001),” stated Shaffelburg, “but was not significantly associated with a reduction in death irrespective of the time between symptom onset and start of antivirals.” 

Findings from this analysis validate current recommendations for using antivirals in adult inpatients and “suggest increased compliance with these guidelines may reduce morbidity and cost,” concluded Shaffelburg.

For continuous infectious disease news coverage from the IDWeek 2017, check back to MPR’s IDWeek page for the latest updates.


Shaffelburg, Z. Impact of Antivirals in the Prevention of Serious Outcomes Associated with Influenza in Hospitalized Canadian Adults: A Pooled Analysis from the Serious Outcomes Surveillance (SOS) Network of the Canadian Immunization Research Network (CIRN). Poster presented at IDWeek 2017; October 4–8, 2017; San Diego, CA.