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Influenza vaccination rates unchanged after LAIV withdrawal
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Despite the withdrawal of recommendation for the live-attenuated influenza vaccine, overall child influenza immunization rates remained unchanged between the 2015-2016 and 2016-2017 influenza seasons, according to a study published in Pediatrics.
In addition, researchers observed that children who had previously received an injectable influenza vaccine were slightly more likely to return for immunizations the following year compared with children who had received LAIV.
“A motivating concern for this study was that the withdrawal of the LAIV recommendation would lower childhood influenza immunization rates and that further interventions might be needed to promote the use of the injectable influenza vaccines among parents who in previous seasons had opted to use an LAIV,” Steve G. Robison, MPH, from the immunization program at the Oregon Heath Authority, and colleagues wrote.
To assess the hypothesis that children who previously received an LAIV might not return for an injectable influenza vaccine, resulting in a noticeable overall decrease in immunization rates, the researchers conducted a study in which child immunization rates from the 2012-2013 season were compared with the 2016-2017 seasons. Data regarding these rates were collected from Oregon’s statewide immunization registry.
Children were additionally matched in groups and selected based on whether they received LAIV or an injectable influenza vaccine within the 2015-2016 season. These cohorts were then compared for immunization status in the 2016-2017 season.
For children between the ages of 2 and 17, influenza immunization rates remained consistent in the 2015-2016 and the 2016-2017 seasons. If a child between the ages of 3 and 10 had previously received an injectable influenza vaccine, they were 1.03 times more likely to receive an injectable influenza vaccine in the 2016-2017 season than children who previously received an LAIV (95% CI, 1.02-1.04). Children between the ages of 11 and 17 who previously received an injectable influenza vaccine were 1.08 times more likely than those who received an LAIV to return for immunization (95% CI, 1.05 to –1.09).
“In this study, the withdrawal of the LAIV had a greater impact on rates of influenza vaccination among adolescents with previous LAIV use than it did among younger LAIV recipients,” Robison and colleagues wrote. “It is possible that the lower rates of injectable influenza vaccine immunization among adolescents who previously received an LAIV withdrawal is also a reflection of their ability to mount effective resistance, verbally or otherwise, to the injectable influenza vaccine should they choose not to receive it.” – by Katherine Bortz
Disclosure: The authors report no relevant financial disclosures.
Perspective
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Ben N. Fogel, MD, MPH
The study by Robison and colleagues used the Oregon immunization registry to show that influenza vaccination rates remained stable after the 2016 Advisory Committee on Immunization recommendation not to offer the live-attenuated influenza vaccination. This is generally consistent with data that Dr. Steven D. Hicks and myself recently published in Vaccine as well as CDC data which both show a minimal decrease in overall vaccination rates. These data should be reassuring to pediatricians who had worried about a large decrease in vaccination rates when the live-attenuated virus was not recommended.
These authors also found that patients who had received the live form of the vaccine in the 2015-2016 season were only slightly less likely to be vaccinated in the 2016-2017 season than those who had been previously vaccinated with the inactivated vaccine. This stands in contrast with our own data which found meaningfully lower rates in 2016-2017 among patients who had previously received the live-attenuated vaccine in 2015-2016.
This discrepancy could be due to the data sources used. Robison and colleagues, using Oregon registry data, found an overall vaccination rate in 2016-2017 of 32.6% compared with CDC reported rates in Oregon of 52.0%. Our own data used health system level electronic medical record data and found an overall vaccination rate of 50.4% compared with CDC reported rates in Pennsylvania of 63.3%. These differences in results highlight the need for varied data sources in assessing seasonal changes in vaccination rates.
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