Sir—We studied the effect of combined pneumococcal conjugate and poly-saccharide vaccinations on the prevention of new AOM episodes in 383 children aged 1—7 years with a history of two or more AOM episodes in the year before study entry. Of these children, 242 (63%) had had four or more episodes per year and complied with the definition of AOM described by Esposito and colleagues. These children had similar rate ratios for recurrence of AOM after pneumococcal vaccination to those who had two to three episodes of disease per year.
During follow up, we diagnosed AOM in accord with the criteria published by the Dutch College of General Practitioners.1
These criteria include clinical symptoms and the otoscopic appearance of the eardrum. Of all 475 AOM episodes observed during follow up, 207 (43%) were diagnosed by three study doctors (two paediatricians and one paediatric resident), 66 episodes (14%) by both an otolaryngologist and a paediatrician, and 207 episodes (44%) by family doctors. Since we used a randomised, double blind study design, possible misclassification will be similar in both the treatment and control groups.
Antibiotic use was similar in the pneumococcal vaccine and control vaccine group. Likewise, the median duration of symptoms per episode and the duration of the use of analgesics and ototopical medication was similar for both groups. Age did not affect these outcomes.
Whether the observed shift in nasopharyngeal carriage from conjugate vaccine to other pneumococcal sero-types is due to replacement or unmasking is an important issue. Our preliminary data show that this shift is mainly caused by replacement.
Due to the restrictive use of antibiotics for AOM in the Netherlands, the proportion of penicillin-resistant pneumococci is low; less than 2%. Pneumococcal vaccination did not, therefore, affect antibiotic resistance.
We conclude that pneumococcal conjugate vaccination combined with polysaccharide vaccination does not prevent AOM in children older than age 1 year who had already had recurrent episodes of AOM before vaccination, nor does it affect the severity of AOM episodes or duration and frequency of antibiotic use in this group of children. At the nasopharyngeal level, a shift from conjugate vaccine to other pneumo-coccal serotypes was observed, mostly due to replacement. With regard to the national immunisation programmes, we believe that if pneumococcal conjugate vaccines are incorporated, they should be administered early in life.2