A study in the September 2017 issue of the journal Pediatrics has found the rate of ear infections in young children has declined significantly since the introduction of vaccines that protect against the bacteria that frequently cause them.

Researchers in Rochester, N.Y., conducted a prospective, longitudinal study of children in their first 3 years of life to look at the epidemiology, etiology and immunobiology of acute otitis media after the introduction of the pneumococcal conjugate vaccines (PCV7 and PCV13).

The study titled, "Epidemiology of Acute Otitis Media in the Post Pneumococcal Conjugate Vaccine Era," published online Aug. 7, followed 615 children over a 10–year period. During that time, 23 percent experienced one or more episodes of acute otitis media and 3.6 percent had three or greater episodes. By 3 years of age approximately 60 percent of children had one or more episodes of acute otitis media and about 24 percent had three or more episodes.

Researchers note that those rates are a significant decrease in cases compared to a previous study done in 1989.

They also found that Streptococcus pneumoniae as the main source of acute otitis media has declined since the introduction of the pneumococcal conjugate vaccines, with Haemophilus influenzae and Moraxella catarrhalis being the main sources now.

While the source of acute otitis media has changed with the introduction of pneumococcal conjugate vaccines, the risk factors have stayed the same. These include child care attendance, family history of acute otitis media and experiencing acute otitis media at a young age, leading the researchers to conclude that the epidemiology but not the risk factors for AOM have undergone substantial changes since the introduction of pneumococcal conjugate vaccines.