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Flu surveillance study tracks pediatric vaccination rates

Jan. 8, 2015, 8:52 AM

A study appearing in the January edition of Pediatrics, led by researchers at Vanderbilt University Medical Center, looks at how Nashville children ages 6 months through 5 years fared over 11 consecutive flu seasons concluding in 2010-11.

Immunization recommendations changed during this period. Ahead of the 2007-08 flu season, for the first time, the immunization schedule published annually by the Centers for Disease Control and Prevention (CDC) recommended annual flu vaccination for most children ages 6 months to 5 years.

For this age group, this vaccination had previously been recommended only for certain high-risk individuals. (Since 2011, the CDC has recommended annual influenza vaccination for nearly everyone.)

Researchers found that in the 2010-11 flu season in Nashville, vaccine uptake among these children reached an estimated 38 percent, compared to single-digit rates reported for the city in the early 2000s, before CDC recommendations were changed.

The authors say it’s too early to see any clear effect from increased vaccination rates on overall flu-associated emergency department visits or hospital admissions. “More data are needed to assess long-term trends in influenza-associated medical care use in children,” they wrote.

Under this Vanderbilt-led, CDC-sponsored surveillance, young children with influenza symptoms are enrolled at selected Nashville health care locations during each flu season, respiratory samples are gathered for laboratory confirmation of influenza and providers are contacted to confirm influenza vaccination.

Over those 11 flu seasons, among this age group the estimated total flu-related emergency department visits in Nashville ranged from 352 to 2,324 per season, and hospitalizations ranged from 7 to 60. During the final season covered by the study, 2010-11, the total estimated flu encounters included 1,418 ED visits and 16 hospital admissions.

“Active surveillance like that conducted at Vanderbilt has been crucial to demonstrate the burden of influenza among young children and to inform public policy,” said one of the authors, Carlos Grijalva, M.D., MPH, associate professor of Health Policy. “Data have revealed the large burden of disease caused by influenza among young children.

The availability of vaccine provides an opportunity to mitigate the impact of this infection, but availability is not enough — the vaccine must be given,” he said.

Other members of the Vanderbilt team included Astride Jules, M.D., MPH; Yuwei Zhu, M.D., MS; Keipp Talbot, M.D., MPH; John Williams, M.D.; Kathryn Edwards, M.D.; William Schaffner, M.D.; and Marie Griffin, M.D., MPH. They were joined by researchers at Wake Forest University and the CDC.

In addition to funding from the CDC, the study was also supported by National Institutes of Health grant TR000445.

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