November 21, 2019
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Seasonal severity, vaccine effectiveness not associated with flu vaccination rates

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Melissa S. Stockwell, MD MPH
Melissa S. Stockwell

Neither seasonal severity nor vaccine effectiveness were associated with influenza vaccination rates over eight recent influenza seasons, although vaccination rates have decreased overall in recent years, according to study findings published in JAMA Pediatrics.

“We as clinicians often think to ourselves that we can ‘predict’ influenza vaccine uptake based on the severity of influenza, particularly in the previous season, or reports of vaccine effectiveness,” Melissa S. Stockwell, MD MPH, associate professor of pediatrics and population and family health at Columbia University’s Mailman School of Public Health, told Infectious Diseases in Children. “We were surprised to see that, at least nationally, that did not seem to be a case.”

Stockwell and colleagues examined CDC data from the 2010-2011 to 2017-2018 influenza seasons regarding vaccine effectiveness, vaccination rates by age group, and annual pediatric severity designations.

They found no association between the severity of an influenza season and vaccination rates across all age groups, with rate ratios of 1.02 (95% CI, 0.93-1.12) for high and very high severity vs. low severity and 1.03 (95% CI, 0.99-1.07) for moderate severity vs. low severity. Severity of the prior season also had no association with vaccination rates, with vaccine effectiveness ranging from 19% to 60% across all years.

“We can’t necessarily rely on outside trends to drive influenza vaccination uptake and therefore, it is up to us as clinicians to make sure to give a strong recommendation for influenza vaccine,” Stockwell said.

Aside from a slight decline in vaccination rates in 2015-2016 following a comparably low vaccine effectiveness rate of 19% during the 2014-2015 season, neither prior nor current year vaccine effectiveness was associated with vaccination rates. Stockwell and colleagues indicated the effects of seasonal severity and vaccine effectiveness may be cumulative, suggesting reduced uptake if these trends continue for multiple successive years.

According to study results published in 2016, vaccination reduces the risk for pediatric influenza-related death by 65% among healthy children and 51% among children with high-risk medical conditions, yet only one in four children who die from influenza are vaccinated. CDC data show that influenza vaccine uptake was 62.6% in kids aged 6 months to 17 years during the 2018-2019 season.

“Decreased influenza vaccine uptake can be attributed to a variety of factors,” Stockwell said. “For some parents, it may be about access. For others, it may be misperceptions about influenza risk and severity, or lack of confidence in vaccination effectiveness, or fears about vaccine safety or side effects. It is important that we strongly recommend influenza vaccine to all our patients 6 months and over and be ready to answer any questions that parents may have.” – by Eamon Dreisbach

References:

CDC. Flu Vaccination Coverage, United States, 2018–19 Influenza Season. https://www.cdc.gov/flu/fluvaxview/coverage-1819estimates.htm. Accessed Nov. 19, 2019.

Disclosures: Stockwell reports receiving grants from the NIH and CDC and being an un-remunerated co-investigator on an investigator-initiated grant from Pfizer.