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Clinical effectiveness of conventional influenza vaccination in asthmatic children
A J Smits1, E Hak, W A B Stalman
1University Medical Center Utrecht, Julius Center for General Practice and Patient Oriented Research, The Netherlands.
Insights
Influenza vaccination may benefit young children with asthma by reducing respiratory illness. Further research is needed to confirm effectiveness in older asthmatic children.
Area of Science:
- Pediatric Respiratory Medicine
- Vaccinology
- Epidemiology
Background:
- Asthma is a common chronic respiratory disease in children.
- Influenza and other acute respiratory diseases pose significant risks to children with asthma.
- Vaccination rates for influenza remain suboptimal in pediatric asthma populations due to safety and efficacy concerns.
Purpose of the Study:
- To evaluate the effectiveness of inactivated trivalent sub-unit influenza vaccine in preventing acute respiratory disease in children with asthma.
- To compare the incidence of respiratory illnesses between vaccinated and unvaccinated asthmatic children.
Main Methods:
- Retrospective cohort study conducted over two influenza seasons (1995-1997) in 22 primary care practices in The Netherlands.
- Included 349 children aged 0-12 years with clinical asthma criteria.
- Compared physician-diagnosed acute respiratory disease episodes (including influenza-like illness, pneumonia, bronchitis, asthma exacerbations) in vaccinated versus unvaccinated children, with adjustments for covariates.
Main Results:
- The overall pooled clinical vaccine effectiveness was 27% (95% CI -7 to 51%), not statistically significant.
- A significant vaccine effectiveness of 55% (95% CI 20-75%) was observed in asthmatic children under 6 years of age.
- No significant protective effect was found in older asthmatic children (-5% effectiveness).
Conclusions:
- Acute respiratory disease incidence is high in asthmatic children during influenza epidemics, particularly in younger children.
- Influenza vaccination shows potential to reduce morbidity in asthmatic infants and pre-school children.
- Larger, preferably experimental, studies are required to definitively establish vaccine benefits, especially in older asthmatic children.
Abstract:
Influenza immunization rates among young asthmatics remain unsatisfactory due to persistent concern about the impact of influenza and the benefits of the vaccine. We assessed the effectiveness of the conventional inactivated trivalent sub-unit influenza vaccine in reducing acute respiratory disease in asthmatic children. We conducted a two-season retrospective cohort study covering the 1995-6 and 1996-7 influenza outbreaks in 22 computerized primary care practices in The Netherlands. In total, 349 patients aged between 0 and 12 years meeting clinical asthma-criteria were included; 14 children were lost to follow-up in the second season. The occurrence of physician-diagnosed acute respiratory disease episodes including influenza-like illness, pneumonia. bronchitis, bronchiolitis, asthma exacerbation and acute otitis media in vaccinated and unvaccinated children were compared after adjustments for age, prior health care and medication use. The occurrence of acute respiratory disease in unvaccinated children was 28% and 24% in the 1995-6 and 1996-7 season, respectively, and was highest in children under 6 years of age (43%). The overall pooled clinical vaccine effectiveness was 27% (95% confidence interval -7 to 51%, P = 0.11) after adjustments. A statistically higher vaccine protectiveness of 55% (95% CI 20-75%, P = 0.01) was observed among asthmatics under 6 years of age compared with -5% in older children (95% CI -81 to 39%). The occurrence of acute respiratory disease among asthmatic children during influenza epidemics is very high, notably in the youngest. Influenza vaccination may reduce morbidity in asthmatic infants and pre-school children. However, larger, preferably experimental, studies are needed to establish the benefits of vaccination, notably in older asthmatic children.