Effect of the DTwP Haemophilus influenzae b conjugate vaccination in Mexico (1999-2007)

The introduction of type b Haemophilus influenzae (Hi b) conjugate vaccines for children as part of immunization schedules has led to a sharp drop in the incidence of Hi b disease. In 1999, the Haemophilus influenzae b DTwP-HB/Hi b vaccine was introduced into the primary immunization program in Mexico. There have been no studies evaluating the vaccine after the widespread immunization in our country. The immune response to Hi b vaccines in different countries varies both quantitatively and qualitatively. Replacement of Hi b strains is expected between pre- and post-vaccination eras. Documentation on these three aspects will be useful for decisions regarding the use of the vaccine. In this review, we show and discuss the potential benefits of vaccination with DTwP-HB/Hi b in Mexico in terms of our collected data obtained during the last 8 years on population genotype variations and on concentration and avidity of IgG antibodies. As the epidemiological follow-up data are missing, the evaluation of the results of these three types of studies, as a whole, allows clarification of the scenario of the protection after vaccination in Mexico, in absence of the drop in cases reports. These results reinforce the findings of postvaccination studies done elsewhere.