More recent studies have shown increases in the proportion of Haemophilus influenzae and Moraxella catarrhalis [type of bacteria that colonizes the upper respiratory tract and can cause ear infections] in the middle-ear fluid of PCV7-immunized children.
We investigated the impact of PCV7 on nasopharyngeal colonization with bacterial pathogens during AOM in the pre- PCV7 and post-PCV7 vaccination eras. Four hundred seventeen children… were enrolled onto AOM studies between September 1995 and December 2004.
Although the nasopharyngeal colonization rate for S pneumoniae was not different between the 3 groups, a significantly higher proportion of PCV7-immunized children with AOM were colonized with M catarrhalis.
Overall, the mean number of pathogenic bacteria types isolated from immunized children (1.7) was significantly higher than in controls (1.4).
The increase in bacterial colonization of the nasopharynx during AOM could be associated with an increase in AOM pathogens and theoretically can predispose PCV7-immunized children with AOM to a higher rate of antibiotic treatment failure or recurrent AOM.