PHILADELPHIA – Receiving a flu shot cut the odds of influenza hospitalizations by 56% among older adults during the 2010-2011 flu season, surveillance data show.
Vaccine effectiveness was consistent across all age groups, even among those aged 75 years or older.
Dr. Fiona Havers
“Continued emphasis on the importance of influenza vaccination among older adults is crucial,” Dr. Fiona Havers said at an annual scientific meeting on infectious diseases.
She reported on 364 adults, aged 50 years and older, who received a flu shot at least 14 days prior to hospital admission for laboratory-confirmed influenza during the 2010-2011 season. Cases were admitted to one of 11 sites participating in the Emerging Infections Program, now FluSurv-Net, and were matched by age and county to 773 controls.
Cases were significantly more likely than were controls to be of nonwhite race (31% vs. 15%), to be Hispanic (7% vs. 2%), to have an annual income less than $35,000 (52% vs. 33%), to have high school or lower-level education (44% vs. 27%), and to have at least two chronic health conditions (72% vs. 36%) (P values < .01 for all).
Estimates of influenza vaccine effectiveness in preventing hospitalization was 33% for all ages, 33% for ages 50-64 years, 45% for ages 65-74 years, and 21% for those 75 years and older, reported Dr. Havers of the influenza division of the Centers for Disease Control and Prevention in Atlanta.
After adjustment for age, gender, race/ethnicity, income, education, recent hospitalization, functional status, and chronic medical conditions, vaccine effectiveness estimates were 56%, 64%, 61%, and 57%, respectively, (P values < .05 for all).
The investigators also looked at influenza subtype and found that after adjustment, vaccination was associated with a significant reduction in the risk of hospitalizations for influenza A H3N2 (51%) and influenza B (95%), but not influenza A H1N1 (46%), likely because of the small number of H1N1 cases, said Dr. Havers, who urged older adults to seek care if they develop symptoms, even if they were vaccinated.
“We know that antiviral treatment is recommended for all older adults with suspected influenza, as they are at high risk for influenza complications, and antiviral drugs work best if given promptly after symptoms develop,” she said in an interview. ID Week comprises the combined annual meetings of the Infectious Diseases Society of America, Society for Healthcare Epidemiology of America, HIV Medicine Association, and Pediatric Infectious Diseases Society.