Seniors still make up the bulk of flu cases, hospitalizations
Last year’s flu vaccine was about as effective as in previous years, but the elderly remained the most impacted by illness, according to an updated report on flu surveillance from the Centers for Disease Control and Prevention (CDC).
Influenza activity during the 2016-17 was moderate, according to the CDC, with low activity in November that increased through December and peaked in February.
The predominant virus for the season was influenza A (H3N2), but influenza B viruses were most commonly reported in later season cases from March through May, the CDC notes.
In terms of who was impacted most last flu season, 8% of the influenza-positive samples tested in public health laboratories were from children from birth to 4 years of age, 30.4% were from individuals aged 5 years to 24 years, and 31.8% were from older adults aged 65 years and up. Influenza A viruses were identified in 70% of the cases in children from birth to 4 years, and in 80% of the cases in adults over age 65. Influenza B viruses were most often reported in individuals aged 5 years to 24 years, and accounted for 28% of those flu cases, according to CDC.
“Last season’s flu vaccine likely prevented thousands of hospitalization and millions of illnesses despite the fact that the vaccine was less effective than we'd like,” Kristen Nordlund, a health communications specialist with CDC told Medical Economics. “While it is clear we need better flu vaccines, it's important that we not lose sight of the important benefits of vaccination with currently available vaccines.”
Hospitalization rates for the 2016-17 flu season were highest among the elderly, with 60% of flu-related hospitalizations occurring in individuals aged 65 and older. Among other age groups, 16.7 per 100,000 of children aged 5 years to 17 were hospitalized, 19.8 per 100,000 adults aged 18 to 49 were hospitalized, 65.1 per 100,000 adults aged 50 to 64 were hospitalized, and 290.5 per 100,000 adults aged 65 and older were hospitalized, according to CDC. Influenza A was diagnosed in 78% of hospitalizations, and influenza B was diagnosed in 21.2% of hospitalizations, according to CDC.
Among adults hospitalized for influenza, 94.1% had at least one other medical condition that placed them at a higher risk of infection or flu-related complications, and 56.4% of children hospitalized for flu had at least one underlying medical condition. Additionally, CDC reported that 26.6% of women aged 15 to 44 that were hospitalized with the flu were pregnant.