Carriage of Haemophilus influenzae among children attending childcare centres in Kuala Lumpur, Malaysia in the post vaccination era: A cross-sectional study

Abstract

Background: Haemophilus influenzae (H. influenzae) is a human upper respiratory tract colonizer which causes wide range of disease especially in children<5 years old and in the elderly. Although worldwide incidence in industrialised countries where Hib vaccination is commonly used has dropped sharply since implementation of H. influenzae type b (Hib) vaccination, there is limited data on the disease burden caused by H. influenzae in Malaysia post vaccination era. A change in predominant serotype from type b to non-b serotypes of H. influenzae in invasive diseases was reported worldwide. We investigated the carriage of H. influenzae post vaccination era among 2-4 years old.

Methodology: Randomly, we collected 436 oropharyngeal swabs from healthy children aged 2-4 years in 30 registered childcare centres in Kuala Lumpur (August 2018-May 2019). Informed consent and written questionnaires were obtained from parents. H. influenzae was identified by standard microbiological methods. Univariable analysis was carried out to describe variables associated with colonization. All variables with p < 0.25 were included in multivariable logistic regression model. A p value < 0.05 was considered significant.

Results: A higher carriage rate was noted among the unvaccinated children (4/28; 14.3%) compared to vaccinated children (16/326; 4.9%) but were not statistically significant. The serotypes were type a (9; 37.5%), type b (5; 20.8%), type c (3; 12.5%), type d (2; 8%), type e (1; 4.2%) and type f (4; 16.7%). Variables like age, basic sanitation, immunization status, body mass index were included in multivariable logistic regression test since p values in univariate analysis were<0.25. Planned sewage system was found to be significant (Adjusted OR, 0.06; 95% CI, 0.01-0.46; p = 0.006).

Conclusion: Fewer carriage rates were observed among children post Hib vaccination era. Hib carriage is still possible after vaccination. The presence non-b serotypes may imply emerging replacement serotypes.

Keywords: Carriage; Haemophilus influenzae; Hib; Non-b serotypes.