Related Experiment Video
Updated: Feb 11, 2026
Detection of Polyfunctional T Cells in Children Vaccinated with Japanese Encephalitis Vaccine via the Flow Cytometry Technique
Published on: September 23, 2022
Effectiveness of influenza vaccination for children in Japan: Four-year observational study using a large-scale
Natsumi Shibata1, Shinya Kimura2, Takahiro Hoshino3
1Department of Drug Development and Regulatory Science, Faculty of Pharmacy, Keio University, Tokyo, Japan.
Insights
Influenza vaccination is clinically effective in Japanese children aged 1-15 years, significantly reducing influenza onset and secondary complications like pneumonia. This real-world study confirms vaccine benefits beyond clinical trials.
Area of Science:
- Public Health
- Epidemiology
- Vaccinology
Background:
- Limited large-scale comparative effectiveness studies of influenza vaccination in Japan.
- Japanese vaccine marketing authorization relies on seroconversion and safety, not real-world effectiveness.
- Need to evaluate influenza vaccine clinical effectiveness in a real-world setting for children.
Purpose of the Study:
- To evaluate the clinical effectiveness of influenza vaccination in children aged 1-15 years in Japan.
- To assess influenza vaccine's ability to prevent influenza and its complications.
- To provide real-world evidence on influenza vaccine effectiveness in a large Japanese population.
Main Methods:
- Conducted a cohort study using a large-scale employee health care claims database (>3 million people).
- Identified vaccination status via influenza vaccination subsidy records.
- Employed a doubly robust method with propensity score adjustment to control for confounding.
Main Results:
- Over 116,000 children participated across four influenza seasons (2010-2014).
- Statistically significant reduction in influenza onset (ORs 0.797-0.894) and complications like pneumonia and respiratory diseases.
- Vaccine effectiveness was particularly notable in younger children and for preventing hospitalizations.
Conclusions:
- Influenza vaccination is clinically effective in Japanese children (1-15 years) from 2010/2011 to 2013/2014.
- The influenza vaccine significantly prevents influenza onset.
- Vaccination effectively reduces secondary complications associated with influenza.
Background:
To date, few large-scale comparative effectiveness studies of influenza vaccination have been conducted in Japan, since marketing authorization for influenza vaccines in Japan has been granted based only on the results of seroconversion and safety in small-sized populations in clinical trial phases not on the vaccine effectiveness. We evaluated the clinical effectiveness of influenza vaccination for children aged 1-15 years in Japan throughout four influenza seasons from 2010 to 2014 in the real world setting.
Methods:
We conducted a cohort study using a large-scale claims database for employee health care insurance plans covering more than 3 million people, including enrollees and their dependents. Vaccination status was identified using plan records for the influenza vaccination subsidies. The effectiveness of influenza vaccination in preventing influenza and its complications was evaluated. To control confounding related to influenza vaccination, odds ratios (OR) were calculated by applying a doubly robust method using the propensity score for vaccination.
Results:
Total study population throughout the four consecutive influenza seasons was over 116,000. Vaccination rate was higher in younger children and in the recent influenza seasons. Throughout the four seasons, the estimated ORs for influenza onset were statistically significant and ranged from 0.797 to 0.894 after doubly robust adjustment. On age stratification, significant ORs were observed in younger children. Additionally, ORs for influenza complication outcomes, such as pneumonia, hospitalization with influenza and respiratory tract diseases, were significantly reduced, except for hospitalization with influenza in the 2010/2011 and 2012/2013 seasons.
Conclusions:
We confirmed the clinical effectiveness of influenza vaccination in children aged 1-15 years from the 2010/2011 to 2013/2014 influenza seasons. Influenza vaccine significantly prevented the onset of influenza and was effective in reducing its secondary complications.
More Related Videos
Related Concept Videos
01:51Vaccinations
01:11Observational Studies
There are three types of observational studies – Prospective, retrospective, and cross-sectional.
Prospective Study
Prospective studies, also known as longitudinal or cohort studies, are carried out by collecting future data from groups sharing similar characteristics. One...
01:11Testing a Claim about Mean: Known Population SD
Estimating a population mean requires the samples to be distributed normally. The data should be collected from the randomly selected samples having no sampling bias. The sample size needed to be higher than 30, and most importantly, the population standard deviation should be already known.
In most realistic situations, the population standard deviation is often unknown, but in rare circumstances, when it...
01:24Testing a Claim about Population Proportion
There are two methods of testing a claim about a population proportion: (1) Using the sample proportion from the data where a binomial distribution is approximated to the normal distribution and (2) Using the binomial probabilities calculated from the data.
The first method uses normal distribution as an approximation to the binomial distribution. The requirements are as follows: sample size is large...
01:19Testing a Claim about Standard Deviation
The hypothesis testing for the claim of population standard deviation (or variance) requires the data and samples to be random and unbiased. The population distribution also must be normal. There is no specific requirement on the sample size as the estimation is based on the chi-square distribution.
As a first step, the hypothesis (null and alternative) concerning the claim about...
01:21Testing a Claim about Mean: Unknown Population SD
Estimating a population mean requires the samples to be approximately normally distributed. The data should be collected from the randomly selected samples having no sampling bias. There is no specific requirement for sample size. But if the sample size is less than 30, and we don't know the population standard deviation, a different approach is used;...