Is Current Hib Vaccine Effectiveness Decreasing in Children?
Vaccine efficacy is high but inversely related to age.
Vaccine efficacy against Haemophilus influenzae serotype b (Hib) has not declined over time or with the combination hexavalent diphtheria, tetanus, and acellular pertussis-hepatitis B virus-inactivated polio virus/Hib vaccine (DTPa-HBV-IPV/Hib), according to a study published in The Lancet: Infectious Diseases.
Susana Monge, PhD, of the Centre for Infectious Disease Control at the National Institute for Public Health and the Environment in Bilthoven, Netherlands, and associates conducted a case-control analysis to determine the efficacy of the hexavalent vaccine and to understand its correlation with increased infection rates among children younger than 5 years.
A total of 159 pediatric patients <5 years of age infected with Hib were included in the study and matched with 1590 control participants with a median age of 1.5 years. Patients were administered either the hexavalent vaccine or a pentavalent vaccine that did not include hepatitis B virus compounds. Vaccines were administered to 91 (57%) patients in the case group and 1408 (89%) patients in the control group.
The investigators reported no significant differences between the various vaccines administered. Total vaccine efficacy was 92.8%. Effectiveness of the pentavalent vaccine was 91.8% (and other control vaccines) compared with 94.0% for the hexavalent vaccine (odds ratio, 0.72).
Results suggested that vaccine efficacy was higher in children between the ages of 1 and 2 years at disease onset (97.1%-99.0%) and lower in children between the ages of 3 and 4 at disease onset (60.7%-82.3%).
“Our results support the current vaccination program, since Hib vaccine effectiveness has not decreased over time or by the introduction of the hexavalent DTPa-HBV-IPV/Hib vaccine,” the authors reported. “Vaccine effectiveness was high but waned with age. Alternative explanations for the increase of Hib disease therefore need to be assessed.”