"Pneumococcus is a bacterium that can cause serious diseases, such as pneumonia, meningitis and blood poisoning," says Sander Fortanier. Sander is researcher at the Julius Center of UMC Utrecht. "The pneumococcus bacterium also plays a role in the development of acute otitis media." In popular terms, this is called ear infection. "Ear infections may be mild, but they are painful and often occur in young children," says Sander.

To protect children against the pneumococcus bacterium, a vaccine against it has been included in the national vaccination program. Children are given a first vaccination when they are between 6 and 9 weeks old. At four months old, they are given the second vaccination, and the third one follows at 11 months old. Sander investigated whether the vaccine also plays a role in preventing ear infections in young children.

His study shows that the vaccination against pneumococci causes children to have ear infections later. "While vaccination does not result in fewer ear infections, it does delay onset of the first one." This delay in the onset of ear infections can be seen mainly in the first three years. This is positive, because especially when a child gets an ear infection before they are ninth months old, there is an increased risk of getting ear infection more frequently. "This also leads to more complaints and hospital visits for toddlers and pre-schoolers," says Sander.
Moreover, ear infections are an important reason for antibiotics use. Sander believes the vaccine can also be effective here: "Vaccination results in reduced treatment with antibiotics and, consequently, fewer hospital visits."

New analyses
According to Sander, the findings from his thesis constitute the first comprehensive estimates of the effect of the pneumococcal vaccine in the Netherlands. He explains: "Before a new vaccine is included in the national vaccination program, the National Institute for Public Health and the Environment always analyzes its effects first. In the past, possible effectiveness against ear infections was included in these analyses, but the effect appears to be overrated. Sander explains that his findings provide a good basis for conducting future economic analyses and renewing old analyses to map out the costs and benefits of the vaccine more effectively. He also recommends the development of new treatment methods for children younger than 9 months of age, as they run the highest risk of ear infection and subsequently have an increased risk of recurrence of the infection.