The impact of the heptavalent pneumococcal conjugate vaccine on the epidemiology of acute otitis media complicated by otorrhea.

BACKGROUND

The heptavalent pneumococcal conjugate vaccine (PCV7) has a considerable effect on the epidemiology of pneumococcal disease. The aim of this observational hospital-based study was to examine the effect of the PCV7 (introduced in our settings in 2004) on the epidemiology of spontaneously draining acute otitis media.

METHODS

Results of all middle ear fluid cultures (n = 3446) obtained from children with acute otitis media complicated with otorrhea before the introduction of immunization (between 2000 and 2003) were compared with those (n = 2134) obtained during a similar post-PCV7 period (between 2005 and 2008). Results of cultures obtained between 2006 and 2008 were examined prospectively, whereas those obtained in previous years were retrospectively reviewed.

RESULTS

Following PCV7 immunization, the rates of otorrhea visits per 10,000 emergency department visits decreased by 38% from 133 to 83 (95% confidence interval of the difference, 42-53; P < 0.001), mainly as a result of the decrease in the incidence of pneumococcal disease (48% decrease-25 vs. 13 per 10,000 emergency department visits; P < 0.001). Otorrhea due to Haemophilus influenzae decreased by 20% (20-16 per 10,000 visits; P < 0.001). Serotype 19A accounted for 1 of 47 (2%) pneumococcal strains in 2006, for 5 of 34 (15%) in 2007, and for 13 of 53 (25%) in 2008 (P for trend: 0.001). In the postvaccine years, penicillin-resistant pneumococcal strains (minimum inhibitory concentration ≥ 2 μg/mL) increased from 4% to 13% (P < 0.001). However, the proportion of pneumococci resistant to macrolides decreased (44% vs. 35%; P = 0.01).

CONCLUSIONS

After the introduction of immunization, otorrhea incidents decreased considerably, mainly because of the decrease in pneumococcal disease. H. influenzae is now the predominant organism. Serotype 19A has increased significantly and is the most common nonvaccine pneumococcal serotype. Penicillin resistance has increased in recent years.