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Flu vaccine did not modify flu severity during 2012-2013 season
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During the 2012-2013 influenza season, the influenza vaccine did not offer additional protection against severe outcomes for hospitalized adults aged 50 years or older, according to results of a data analysis.
“We did not see substantial differences in influenza severity by vaccination status in older adults hospitalized with laboratory-confirmed influenza during the 2012-2013 influenza season, despite the high hospitalization rates among persons aged 65 years or older,” Carmen S. Arriola, DVM, PhD, of the Epidemic Intelligence Service Program of the CDC, and colleagues wrote. “In years in which the vaccine is a better match to circulating viruses, and consequently has better effectiveness against influenza virus infection, we might see a stronger effect of influenza vaccination on clinical outcomes.”
The researchers obtained data from the Influenza Hospitalization Surveillance Network for the 2012-2013 flu season. The researchers included 5,614 patients who were hospitalized with laboratory-confirmed flu. Of these patients, 3,101 received the flu vaccine at least 12 days before hospitalization, they wrote in the Journal of Infectious Diseases. They used the following clinical outcomes: pneumonia diagnosis, ICU length of stay and hospital length of stay.
Fourteen percent of the patients were admitted to ICUs, and 2% died, the researchers wrote. Thirty-three percent of the 5,462 patients who had a chest radiograph taken within 3 days of admission were diagnosed with pneumonia. Median length of ICU and hospital stays was 3 days.
Although the 2012-2013 flu season was considered moderately severe, with a large increase in hospitalizations among older adults, there was no difference in disease severity based on vaccination status, according to Arriola and colleagues.
In the propensity score model, vaccinated patients who were aged 50 to 64 years had a shorter length of ICU stay (HR = 1.84; 95% CI, 1.12-3.01) than those were unvaccinated. The researchers saw a similar trend in patients aged 65 years to 74 years, although this did not reach statistical significance. – by Colleen Owens
Disclosure: Arriola reports no relevant financial disclosures. Please see the full study for a list of all other authors’ relevant financial disclosures.
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