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Seasonal influenza vaccine effectiveness among children, 2010-2012
Chuanxi Fu1, Qing He, Zhaotian Li
1Guangzhou Center for Disease Control and Prevention, Guangzhou, China.
Insights
Annual influenza vaccination is recommended for children aged 6-59 months, providing moderate protection. Vaccine effectiveness (VE) was 73.2% in 2010-2011 and 52.9% in 2011-2012, highlighting the need for yearly immunization.
Area of Science:
- Pediatrics
- Immunology
- Public Health
Background:
- Seasonal influenza vaccine effectiveness (VE) requires annual assessment due to evolving circulating strains.
- This study evaluated the trivalent inactivated influenza vaccine's VE in Guangzhou, China, during the 2010-2011 and 2011-2012 seasons.
Purpose of the Study:
- To assess the influenza vaccine effectiveness (VE) in children aged 6-59 months in Guangzhou, China.
- To determine the VE of the trivalent inactivated influenza vaccine for the 2010-2011 and 2011-2012 influenza seasons.
Main Methods:
- A 1:2 matched case-control study was conducted using laboratory-confirmed influenza cases and randomly selected controls.
- Participants were children aged 6-59 months in Guangzhou, matched by date of birth, gender, and residence.
- Vaccination data were retrieved from the Children's Expanded Programmed Immunization Administrative Computerized System.
Main Results:
- Vaccine effectiveness (VE) was 73.2% (95% CI, 52.2-85.0%) for the 2010-2011 season and 52.9% (95% CI, 42.1-61.7%) for the 2011-2012 season.
- VE decreased from 68.9% in January-March to 48.4% in April-June.
- A total of 1255 influenza cases and 2510 matched controls were analyzed across the two seasons.
Conclusions:
- The trivalent inactivated influenza vaccine provided moderate protection in vaccinated children aged 6-59 months.
- Annual influenza vaccination is recommended, even for children vaccinated in the previous season, due to potential waning immunity and strain changes.
- This post-licensing study underscores the importance of ongoing VE monitoring and vaccination campaigns.
Background:
The annual differences in the seasonal influenza vaccine and the circulating strains make it necessary to assess influenza vaccine effectiveness (VE) yearly. We assessed the effectiveness of the trivalent inactivated influenza vaccine for the 2010-2011 and 2011-2012 influenza seasons among children in Guangzhou, China.
Methods:
We conducted a 1:2 matched case-control study based on date of birth (±7 days), gender, and area of residence. The influenza cases from surveillance sites in Guangzhou were laboratory-confirmed during the 2010-2012 seasons. The controls were randomly selected from children aged 6-59 months in the Children's Expanded Programmed Immunization Administrative Computerized System. The influenza vaccination information for both cases and controls was retrieved from this system.
Results:
We analyzed the vaccination information for 1255 influenza cases and 2510 matched controls in 2 influenza seasons in Guangzhou, China. We found that the VE for vaccination during the 2010-2011 and 2011-2012 seasons of virus circulation was 73·2% (95% confidence interval (CI), 52·2-85·0%) and 52·9% (95% CI, 42·1-61·7%), respectively. The VE decreased from 68·9% (95% CI, 57·5-77·2%) in the period between January and March to 48·4% (95% CI, 33·8-59·7%) in the period between April and June.
Conclusions:
This post-licensing study of VE found moderate protection against influenza for vaccinated children aged 6-59 months. Although the influenza vaccine strains for the 2010-2011 and the 2011-2012 seasons were the same, our study indicated that annual vaccination is recommended even for those who received the vaccine during the previous season.
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