Strep Vaccine Benefits Kids Prone to Ear Infection

WINSTON-SALEM, N.C., April 3 -- Children prone to frequent ear infections are the major beneficiaries of the new pneumococcal conjugate vaccine, according to researchers here.

As use of the vaccine has increased, the occurrence of ear infections in children under the age of two has decreased significantly, investigatiors have found.

It turns out that the decrease was primarily from the minority of children with frequent ear infections rather than the majority with occasional disease. said Katherine Poehling, M.D., of Wake Forest Baptist Medical Center, and colleagues, in a population based-study in Tennessee and New York.

The investigators, reporting in the April issue of Pediatrics, found that since the era of the vaccine began in 2000, recurrent otitis media fell by up to 28% and the insertion of pressure-equalizing tubes by up to 23%. The research was conducted while Dr. Poehling was at Vanderbilt in Nashville.

The vaccine, which targets seven strains of Streptococcus pneumoniae known to cause otitis media, was licensed in 2000 and routine administration began in the summer of that year. Since then several studies have shown a 20% decline in physician visits for the condition, Dr. Poehling and colleagues reported

But the source of the decline was not clear, Dr. Poehling said.

So the researchers looked at four birth cohorts -- those born between July 1, 1998 and June 30, 1999, and the same 12-month periods in 1999-2000, 2000-2001, and 2001-2002 -- in Tennessee and upstate New York. They compared rates of frequent otitis media and ear tube insertion over time, using the earliest cohort as a reference group.

The 150,000 Tennessee children were enrolled in the state's managed care program, TennCare, which includes half of the state's children and all of those enrolled in Medicaid.

The 27,000 New York children were enrolled in private managed care organizations that covered about 70% of children in the Rochester area.

Frequent otitis media was defined as three cases within six months or four within a year. The proportion of children who got at least three doses of the vaccine by two years of age rose from less than 1% for the 1998-1999 birth cohort to about 75% in 2000-2001 cohort.

When the 2000-2001 cohort was compared with the 1998-1999 group, the researchers found:

• The risk of developing frequent otitis media in Tennessee dropped 17% and in New York fell 28%. The hazard ratios were 0.83 and 0.72, respectively, with 95% confidence intervals from 0.81 to 0.86 and 0.67 to 0.77.
• The risk of having a tube inserted fell in Tennessee by 16% and in New York by 23%. The hazard ratios were 0.84 and 0.77, respectively, with 95% confidence intervals from 0.79to 0.89 and 0.65 to 0.90.

Interestingly, in the 2001-2002 cohort, the New York children continued to have similar reductions compared with 1998-1999, but the numbers looked different in Tennessee. For the latest Tennessee cohort, frequent ear infections were less than in 1998-1999, but higher than the 2000-2001 numbers and tube-insertions were similar to those in the base year.

The Tennessee observation is "surprising and potentially important" because most of those children would have been vaccinated, the researchers said. Possible explanations include an increase in the use of medical services, which might obscure the vaccine effect, or an increase in disease caused by organisms not targeted by the vaccine, they said.

Because the finding includes children from different regions and socioeconomic backgrounds, Dr. Poehling said she thinks the results are generalizable to the U.S. as a whole.

But, she said, "although these results are very exciting, we need to carefully monitor the trends in ear infections because pneumococcal strains not included in the vaccine may increase and potentially diminish these gains."