BACKGROUND: Residents of long-term care facilities (LTCFs) are at high risk of influenza complications including hospitalization and death. Influenza can be introduced into LTCFs by health-care personnel (HCP), newly admitted residents and by visitors. Higher influenza vaccine coverage among HCP has been associated with lower LTCF resident influenza-like-illness (ILI) and death. During the 2014/15 influenza season in the United States, 99.6% of influenza A subtyped at public health laboratories was A/H3N2, but the Centers for Disease Control and Prevention estimated vaccine effectiveness against influenza A/H3N2 was only 18%. Nationwide, the influenza- associated hospitalization rate among people ≥65 years was 45% higher than the previous highest recorded rate (2014/15 season: 266.1/100,000 population; 2012/13: 183.2/100,000 population). The objective of this study was to evaluate the relationship between LTCF resident and employee vaccination coverage and resident hospitalizations during the 2014/15 influenza season in Pennsylvania.
METHODS: Pennsylvania conducts annual systematic surveillance of influenza outbreaks in LTCFs, defined as 1 laboratory-confirmed influenza case plus 1 additional case of ILI or 2 cases of ILI within 72 hours. Facility demographics included number of residents and employees. Outbreak outcomes included number of ILI cases, hospitalizations and deaths among both residents and employees. Influenza vaccination during Oct 1, 2014-May 1, 2015 was categorized for residents (low: 0-79%; medium: 80-89%; high: 90-100%) and employees (low: 0-59%; medium: 60-80%; high: 90-100%). Outcomes and vaccination categories were compared using ANOVA/Welch’s test with Bonferroni corrections for multiple comparisons.
RESULTS: During the 2014/15 influenza season, 540 outbreaks were identified in Pennsylvania LTCFs and 481 outbreaks with available final reports were included in final analyses. Most LTCFs had ≤150 residents (384, 80%) and most had ≤200 employees (357, 74%). Seventy percent of facilities had medium or high resident vaccination coverage (low: 118 facilities, 30%; medium: 106, 27%; high: 163, 42%); these facilities reported fewer mean resident hospitalizations (low: 3.5% of residents hospitalized, Standard deviation = 4.9; medium: 1.8%, SD=2.5; high: 2.6%, SD=4.9, ANOVA p=0.0108). Fifty-six percent of facilities had medium or high employee vaccination coverage (low: 168, 44%; medium: 108, 28%; high: 110, 28%); these facilities reported fewer mean resident hospitalizations (low: 3.4%, SD = 5.1; medium: 1.7%, SD = 3.1; high: 1.7%, SD = 2.2, ANOVA p=0.0006).
CONCLUSIONS: Despite a mismatch between circulating A/H3N2 influenza viruses and the vaccine strain during the 2014/15 influenza season, higher resident and employee influenza vaccine coverage was still strongly associated with lower percentage of resident hospitalizations.