Abstract
We assessed vaccine effectiveness (VE) against medically attended, laboratory-confirmed influenza in children 6 months to 15 years of age in 22 hospitals in Japan during the 2013–14 season. Our study was conducted according to a test-negative case-control design based on influenza rapid diagnostic test (IRDT) results. Outpatients who came to our clinics with a fever of 38°C or over and had undergone an IRDT were enrolled in this study. Patients with positive IRDT results were recorded as cases, and patients with negative results were recorded as controls. Between November 2013 and March 2014, a total of 4727 pediatric patients (6 months to 15 years of age) were enrolled: 876 were positive for influenza A, 66 for A(H1N1)pdm09 and in the other 810 the subtype was unknown; 1405 were positive for influenza B; and 2445 were negative for influenza. Overall VE was 46% (95% confidence interval [CI], 39–52). Adjusted VE against influenza A, influenza A(H1N1)pdm09, and influenza B was 63% (95% CI, 56–69), 77% (95% CI, 59–87), and 26% (95% CI, 14–36), respectively. Influenza vaccine was not effective against either influenza A or influenza B in infants 6 to 11 months of age. Two doses of influenza vaccine provided better protection against influenza A infection than a single dose did. VE against hospitalization influenza A infection was 76%. Influenza vaccine was effective against influenza A, especially against influenza A(H1N1)pdm09, but was much less effective against influenza B.
Highlights
Influenza vaccination is the most effective method of preventing influenza virus infection and its potentially severe complications, and vaccine efficacy from randomized control trials [1,2,3] and vaccine effectiveness (VE) from observational studies [4,5,6,7] in healthy children has been reported to be 40%-70%
VE has generally been interpreted in the context of vaccine matches with circulating strains, low VE has recently been reported to be related to mutations in the egg-adapted H3N2 vaccine strain rather than to antigenic drift in circulating viruses [8,9]
High VE was shown in the influenza A group (63%), and VE was as high as 77% in the group with confirmed A(H1N1)pdm09 infection
Summary
Influenza vaccination is the most effective method of preventing influenza virus infection and its potentially severe complications, and vaccine efficacy from randomized control trials [1,2,3] and vaccine effectiveness (VE) from observational studies [4,5,6,7] in healthy children has been reported to be 40%-70%. VE has generally been interpreted in the context of vaccine matches with circulating strains, low VE has recently been reported to be related to mutations in the egg-adapted H3N2 vaccine strain rather than to antigenic drift in circulating viruses [8,9]. Low VE against influenza A/H3N2 was reported during the 2012–13 season, especially in the elderly (-11% and 9%) [10,11], even though the vaccine and epidemic strains matched. By contrast, during the 2013–2014 season, influenza A(H1N1)pdm virus caused major epidemics in the United States (U.S.) and Canada, and high VE (60% to 75%) against influenza A (H1N1)pdm virus was reported [12,13]. The vaccine and epidemic strains matched in the 2013–2014 season. Since there was a marked change in VE between the 2012– 2013 season and 2013–2014 season because of the difference in epidemic influenza subtypes, it has become very important to estimate VE every season to monitor the performance of current influenza vaccine
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a callDisclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.
