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Repeated inactivated influenza vaccine may increase protection against respiratory illness
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Repeated inactivated influenza immunization appeared to increase long-term protection against some respiratory illness episodes in children with pre-existing medical conditions, according to findings recently published in Annals of Family Medicine.
“Data on the impact of repeated influenza immunization in children with preexisting medical conditions are ... lacking completely,” Marieke L.A. de Hoog, PhD, of the Julius Center for Health Sciences and Primary Care, University Medical Center Utrecht in The Netherlands, and colleagues wrote.
Researchers analyzed electronic health records of 4,183 children with pre-existing medical conditions to assess if prior immunization altered the impact of inactivated influenza vaccine on primary care–diagnosed respiratory illness episodes during influenza season.
De Hoog and colleagues found that adjusted estimates showed lower odds for respiratory illness in current year–immunized children with previous inactivated influenza vaccine vs. those without the vaccine (OR = 0.61; 95% CI, 0.47-0.78 for current year immunized and one inactivated influenza vaccine in the 2 years prior; OR = 0.85; 95% CI, 0.68-1.07 for current year immunized and two or more inactivated influenza vaccines in the 3 years prior, including prior year).
“This study shows that protection against seasonal [respiratory illness] is not attenuated after repeated annual inactivated influenza vaccine immunization in children with preexisting medical conditions. Interestingly, our findings suggest that repeated inactivated influenza vaccine immunization may even increase protection,” de Hoog and colleagues wrote.
“Previous studies have focused primarily on laboratory-confirmed influenza, and we are the first to demonstrate this effect for seasonal respiratory illness,” they added. – by Janel Miller
Disclosures: The authors report no relevant financial disclosures.
Perspective
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Kathryn Edwards, MD
In this paper, investigators from the Netherlands investigate the impact of repeated influenza vaccine in children with underlying medical conditions. There have been some data in adults that suggest that repeated influenza vaccines may not work as well if you give them repeatedly each year. This study investigates that in children.
De Hoog and colleagues took a large database of children with underlying conditions were evaluated for influenza-like illness, acute respiratory infections, and asthma. Those children that received the vaccine in multiple years were compared with those who were immunized only in that influenza season (they did not do laboratory-based studies to confirm influenza in those patients that had influenza-like illness). These researchers found there was no negative impact on the children from being immunized in earlier years, and indeed the children appeared to be better protected.
The study is reassuring but did not confirm the actual laboratory-confirmed rate of influenza, which was a limitation of the study. Primary care doctors should continue to encourage all patients and particularly high-risk patients to be immunized each year. These results should reinforce the recommended immunization guidelines.
Vanderbilt University School of Medicine
Division of Infectious Diseases
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