Perspective

Seasonal severity, vaccine effectiveness not associated with flu vaccination rates

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.

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.

    Perspective
    Sean T. O

    Sean T. O'Leary

    Influenza vaccination saves thousands of lives in the U.S. every year, yet uptake remains suboptimal.

    This study was performed to assess if media reports regarding an influenza season’s severity or vaccine effectiveness impacted vaccination rates. For many years, there has been a sense among clinicians and public health professionals that some parents base their influenza vaccination decisions in a reactionary way in response to reports in the media.

    For example, when I was primary care pediatrician in Fort Collins, Colorado, in the 2003-2004 influenza season, there was a highly publicized early season influenza-associated pediatric death, and we had several heated arguments among parents in our waiting room vying for spots in line to get their children the influenza vaccine. It turns out though, based on the findings of this study, that we don’t really see this phenomenon at the population level. I think these findings speak to the complexity of influenza vaccination decisions for some families.

    While the evidence is clear that influenza vaccination prevents pediatric deaths, ICU admissions and influenza-like illness, many parents still refuse influenza vaccination for their children despite strong recommendations from providers and use of evidence-based techniques for increasing uptake, such as reminder/recall and standing orders for vaccination.

    Concerningly, the authors of this study noted a slight downward trend in childhood influenza vaccination rates after many years of steady increase. I agree with the authors’ conclusions. We are in dire need of effective interventions to address parental refusal of influenza vaccine.  

    • Sean T. O'Leary, MD, MPH
    • Associate professor of pediatrics-infectious diseases
      University of Colorado Denver Anschutz Medical Campus
      Member, AAP’s Committee on Infectious Diseases

    Disclosures: O’Leary reports no relevant financial disclosures.