A recent study by RIVM National Institute for Public Health and the Environment and AMC shows that the effectiveness of vaccination against Hib is still high. The slight increase in the number of patients with Hib disease in 2016 cannot be explained by a reduced effectiveness of the Hib vaccine. This research was published in The Lancet.
The study evaluates the effectiveness of Hib vaccines that have been sequentially used in the Netherlands. Hib is the abbreviation for the bacterium Haemophilus influenzae type b. The effectiveness of the currently used DKTP-Hib-HepB vaccine is 94% and is comparable to the effectiveness of previously used vaccines (DKTP-Hib combination vaccine and separate Hib vaccine). Protection of the Hib vaccine decreases with age, from 99% in children aged 1 and 2 years, to 61% in children aged 3 and 4 years; this was the case for the currently used DKTP-Hib-HepB vaccine as well as for the vaccines that were previously used.
Increase in Hib disease
In 2016, an increase in cases of Hib disease in children younger than 5 years was observed, from 9 cases in 2014 to 21 in 2016. In 1992, before the introduction of Hib vaccination, there were 280 cases of Hib disease in children younger than 5 years.
The current study compared the effectiveness of the currently used DKTP-Hib-HepB vaccine with that of previously used vaccines; a lower effectiveness of the current vaccine could be a possible explanation for the recent increase in Hib patients. A total of 159 cases of invasive Hib disease in children younger than 5 years occurring between 2003 and 2016 were studied, as well as a random sample of 1590 healthy children from the national vaccination register Praeventis. Their vaccination status against Hib, as well as the type of vaccine they received was studied. The results show that the effectiveness of the vaccination program against Hib disease in the Netherlands is still high and that the increase in Hib disease cannot be explained by a lower effectiveness of the DKTP-Hib-HepB vaccine. The cause of the increase in Hib disease is currently unknown. It could possibly be due to random fluctuation over time. The incidence of Hib disease is being constantly monitored.
In young children, infection with Hib can be severe and cause meningitis, epiglottitis, or severe pneumonia. The vaccine against Hib disease has been included in the Dutch National Immunisation Programme since 1993. Various vaccines against Hib have been used over the years. Since 2011, the vaccine used is one in which Hib vaccination is combined with vaccination against diphtheria, tetanus, whooping cough, polio and hepatitis B, the so-called DKTP-Hib-HepB vaccine.