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Haemophilus influenzae b-vaccination: the urgency for timely vaccination
R von Kries1, O Böhm, A Windfuhr
1Institute of Social Paediatrics, Kinderzentrum München, Germany.
Insights
Suboptimal Haemophilus influenzae type b (Hib) vaccination schedules significantly increase infection risk in children. Completing Hib vaccinations on time, including boosters, is crucial for effective protection against invasive Hib disease.
Area of Science:
- Pediatric Infectious Diseases
- Vaccinology
- Epidemiology
Background:
- Systemic Haemophilus influenzae type b (Hib) infections pose a significant risk to young children.
- Recent data indicate an increase in Hib cases among vaccinated children, suggesting potential issues with vaccination timeliness or completeness.
Purpose of the Study:
- To investigate the association between age-related suboptimal vaccination status and the risk of systemic Hib infections in children.
- To quantify the increased risk of Hib infection due to incomplete or delayed vaccination schedules.
Main Methods:
- A case-control study was conducted in West Germany between July 1992 and August 1994.
- Cases of systemic Hib infections were identified via active hospital surveillance.
- Six age-matched population controls were recruited per case; only vaccinated individuals were included.
Main Results:
- Suboptimal vaccination for age was found to increase the risk of systemic Hib infections by a factor of 4.74 (95% CI: 2.17-10.34).
- After adjusting for confounders, the odds ratio for suboptimal vaccination remained significant at 4.39 (95% CI: 1.74-11.07).
- The risk was not associated with the specific vaccine type used; lack of a booster vaccination in children over 18 months showed a particularly high risk.
Conclusions:
- On-schedule and complete Haemophilus influenzae type b (Hib) vaccinations are essential for the effectiveness of vaccination programs.
- Booster vaccinations between 12 and 18 months are critical when using PRP-D, HbOC, and OMP vaccines for primary immunization.
Unlabelled:
In Germany the annual number of systemic Haemophilus influenzae cases in unvaccinated children aged 3-60 months has recently been exceeded by the number of cases in children vaccinated at least once with the PRP-D, HbOC or OMP vaccines, which until 1995 have almost exclusively been used for H. influenzae b (Hib) vaccination. Most of the vaccinated children however could already have had more vaccinations at onset of disease. How much does an age-related suboptimal vaccination status increase the risk for systemic H. influenzae infections? A case control study was performed in West Germany. Cases with systemic H. influenzae infections were ascertained between 7/92 and 8/ 94 with an ongoing active hospital surveillance programme. Six age-matched population controls per case were recruited at random. Only vaccinated cases and controls were included in the study. The main exposure analysed in this study was suboptimal vaccination at censoring; for censoring ages (age at disease onset in cases and corresponding age in matched controls) > 6 months: one vaccination in 1st year only; > 18 months: two (three for combined vaccines with Hib + DT or DPT in one syringe) vaccinations in the 1st year of life but no booster vaccination. Suboptimal vaccination for age increased the risk for systemic H. influenzae infections by a factor of 4.74 (95%-CI 2.17-10.34). Following adjustment for confounders the odds ratio was 4.39 (95%-CI 1.74-11.07). Subgroup analyses showed that this risk was not related to the type of vaccine used. The risk for "no booster vaccination" in children aged > 18 months appeared even greater than the risk associated with one vaccination in the 1st year only.
Conclusions:
On schedule and complete Hib vaccinations are essential for an optimal effectiveness of Hib vaccination programmes. Booster vaccinations between 12 and 18 months are important if the PRP-D, HbOC and OMP vaccines are used for primary vaccination.