Influence of pneumococcal conjugate vaccines on acute otitis media in Japan

Objective

This study investigated: (i) changes in the incidence of acute otitis media (AOM) following introduction of public funding for free inoculation with 7- and 13-valent pneumococcal conjugate vaccines (PCV7 and PCV13, respectively) and (ii) changes in the rate of myringotomies for AOM (MyfA) in children 1 year following the publication of the first edition of the clinical practice guidelines for the diagnosis and management of AOM in children in Japan.

Methods

PCV7 was launched on the Japanese market in 2010 and gained public funding in 2011. PCV7 was replaced with PCV13 in November 2013. Using the Japan Medical Data Center Claims Database, an 11-year study conducted between January 2005 and December 2015 investigated the decline in the incidence of visits to medical institutions (VtMI) due to all-cause AOM in children <15 years. The rate of MyfA from January 2007 to December 2015was also investigated and changes before and after introduction of public funding for PCV7 (pfPCV7) and PCV13 (pfPCV13) for children were examined. Statistical data for the age group between 10 years and <15 years served as the control. An analysis was conducted to examine changes for each age group, from infants that had received PCVs to children <5 years. Statistical analysis was performed using the chi-square test and Ryan’s multiple comparison tests. Ryan’s multiple comparison tests were applied at a 5% level of significance. Due to significant changes in the guidelines on the indications for myringotomy introduced in 2013, statistical analysis of the rate of MyfA was limited to the pre- and post-PCV7 period.

Results

After introduction of pfPCV7 and pfPCV13, no significant suppression of the incidence of VtMI was observed in any age group. There was a gradual decline in the rate of MyfA after 2011. Compared to the control group, significant differences in all age groups from infants to children <5 years were observed (p < 0.009, chi-square test). Within 2 years after the introduction of PCV7, a significant decline in the rate of MyfA was observed in 1- and 5-year-olds using Ryan’s multiple comparison tests at a 5% level of significance.

Conclusion

The preventative effect of PCVs on AOM was not established in this study. There was, however, a significant decline in the rate of MyfA among 1- and 5-year-olds. Taking into consideration past studies, PCV7 may play a role in preventing the aggravation of AOM in 1-year-olds. When evaluating the effectiveness of PCVs, measures to evaluate severity may be as important as evaluating disease prevention.