A pneumonia vaccine reduces the incidence of acute otitis media (AOM, acute ear infection) caused by the bacterium Streptococcus pneumoniae by 34 percent and reduces the overall incidence of AOM by 6 to 8 percent. However, a new study found that children with AOM who were immunized with the heptavalent pneumococcal conjugate vaccine (PCV7) were as likely as nonimmunized children to have nasopharyngeal colonization with S. pneumoniae and were more likely to have other types of bacteria in their nasopharynx. The nasopharynx is located at the back of the throat and has two passages leading to the inner ear, through which bacteria can travel.
The study, supported in part by the Agency for Healthcare Research and Quality (HS10613), raises concern that colonization of the nasopharynx of children with AOM with multiple types of bacteria could increase the likelihood of multiple AOM pathogens. This, in turn, could possibly lead to more children failing to respond to a single-antibiotic treatment for an ear infection. It could also lead to increased risk for developing recurrent AOM after antibiotic treatment. Researchers advise continued vigilance in observing the effect of PCV7 on acute ear infections.
They specifically investigated the impact of PCV7 on nasopharyngeal colonization with S. pneumoniae, Haemophilus influenzae, and Moraxella catarrhalis during AOM in the pre-PCV7 and post-PCV7 vaccination eras. They enrolled 417 children (6 months to 4 years of age) in AOM studies between September 1995 and December 2004. Of these, 200 were enrolled before the vaccine’s use (historical controls), and 217 were enrolled after initiation of PCV7 vaccination (101 were underimmunized, that is missed 1 or 2 doses due to early shortage of vaccines, and 116 were immunized). The colonization rate for S. Pneumoniae was not different between the three groups. However, a significantly higher proportion of PCV7-immunized children with AOM were colonized with M. Catarrhalis (74 percent) compared with historical controls (56 percent) and the underimmunized group (62 percent). Overall, the mean number of pathogenic bacteria types isolated from immunized children (1.7) was significantly higher than in controls (1.4).
See “Effect of pneumococcal conjugate vaccine on nasopharyngeal bacterial colonization during acute otitis media,” by Krystal Revai, M.D., M.P.H., David P. McCormick, M.D., Janak Patel, M.D., and others in the May 2006 Pediatrics 117(5), pp. 1823-1829.