Effectiveness of Trivalent Inactivated Influenza Vaccine in Children Estimated by a Test-Negative Case-Control Design Study Based on Influenza Rapid Diagnostic Test Results

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.

High Vaccination Coverage among Children during Influenza A(H1N1)pdm09 as a Potential Factor of Herd Immunity

“…As for the age groups, the effectiveness of the seasonal H1N1 influenza vaccine among individuals has been previously reported [12,17,18,19,20]. In particular, this study revealed that vaccination had a strong preventative effect in people aged 1–3 years, 4–6 years, 20–29 years, and 30–39 years.…”

Effectiveness of vaccination and wearing masks on seasonal influenza in Matsumoto City, Japan, in the 2014/2015 season: An observational study among all elementary schoolchildren

“…Moreover, differences in the effectiveness of vaccination between children in elementary school and kindergarten may reflect differences in activities (Suzuki et al, 2014), suggesting that differences in vaccination effectiveness between higher and lower grade elementary schoolchildren may have been due to differences in activity. In addition, vaccination was recently reported to be less protective in older than in younger schoolchildren (Shinjoh et al, 2015) and this may explain partly the disparity of effectiveness found in the age groups in the present study. We could only report the difference of vaccine effectiveness which this study found without giving a clear explanation of the cause, to which extent this is a limitation and its discussion may be limited.…”

“…Although vaccination is regarded as the most effective method of controlling the spread of influenza (CDC, 2016a, WHO, 2016), studies are needed to explore the effectiveness of vaccination and to determine the optimal type of vaccine, age at vaccination, and matching of vaccine to virus subtype (DiazGranados et al, 2012). Moreover, the effectiveness of vaccination has been found to differ among age groups (Shinjoh et al, 2015). Longitudinal epidemiological studies focused on the effectiveness of vaccines, including over several generations, are necessary.…”

Japanese Surveillance Systems and Treatment for Influenza

“…In Japan, most of ambulatory patients start NAI treatment within 1–2 days of influenza onset. Studies have shown that 80–95 % of influenza patients in Japan visit a medical facility within 48 h of onset and started the treatment [54, 55]. Other studies have shown that earlier initiation of antiviral therapy is associated with improved clinical outcomes in all populations [52, 56–58].…”