Relationship Between Antiviral Chemoprophylaxis and Resident Deaths During Influenza Outbreaks In Long-Term Care Facilities During the 2010/11 Influenza Season In Pennsylvania

Background: Influenza disproportionately impacts long-term care facility (LTCF) residents; 80% of seasonal influenza-related deaths occur among the elderly. Antiviral post-exposure chemoprophylaxis is recommended for contacts of influenza cases during institutional outbreaks to prevent transmission.

Objectives: To evaluate the relationship between reported resident hospitalizations and deaths and antiviral treatment and chemoprophylaxis during LTCF influenza outbreaks.

Methods: In Pennsylvania, a single lab-confirmed influenza case in an LTCF resident is considered an outbreak. A standard data collection worksheet is used to assess facility characteristics, outbreak size and duration, laboratory confirmation, treatment/prophylaxis, and influenza vaccination. Outbreaks reported between September 2010 and April 2011 were evaluated. Outbreaks were excluded if final reports or laboratory confirmation were unavailable. Analysis was performed using SAS 9.2.

Results: During the 2010/11 influenza season, 199 influenza outbreaks were reported; 20 (10%) were excluded because of missing data. The 179 outbreaks occurred in 158 facilities and included 2,235 total resident illnesses (median per outbreak=7, range 1--136). Hospitalizations occurred in 119 outbreaks (66%); deaths occurred in 22 (12%). Antiviral treatment was given in 91% of outbreaks; prophylaxis in 49%. Oseltamivir was the most commonly used drug for treatment (98%) and prophylaxis (90%). Facilities reporting deaths were more likely than those not reporting deaths to have provided prophylaxis to exposed well residents (OR = 3.5, 95% CI=1.2, 10.3). This trend was not evident with respect to hospitalizations (OR = 1.0, 95% CI=0.5, 2.0).

Conclusions: This study found LTCFs with fatalities during an influenza outbreak were more likely to prescribe prophylaxis than those not reporting fatalities. Because it is unknown whether prophylaxis was administered before or after the fatality, it is unknown whether prophylaxis was ineffective or simply reflects outbreak severity. Future studies should collect more detailed epidemiologic data on LCTF outbreaks to evaluate the impact of antiviral medication prescribing as a prevention and control measure in LCTFs.