Frequent OM less likely since PCV7 introduced

May 2007

Children who were born since the heptavalent pneumococcal conjugate vaccine licensure were less likely to develop frequent otitis media, according to the findings of a recent study.

The study was conducted by the New Vaccine Surveillance Network with researchers from Vanderbilt University Medical Center, Nashville, Tenn., the University of Rochester School of Medicine and Dentistry, Rochester, New York and the National Center for Immunization and Respiratory Diseases at the CDC, Atlanta, Ga.

The researchers studied children in New York and Tennessee from birth to age 5 years to determine the rates of frequent OM and the insertion of pressure-equalizing tubes. Children in both regions experienced a reduction in frequent OM and tube insertion; however, frequent OM and rates of tube insertion remained stable in the children in the New York cohorts whereas children in the Tennessee cohort born in 2001 to 2002 experienced a slight increase.

Pediatrics published the findings.

OM, tube insertion rates

The study consisted of four birth cohorts: children born from 1998 to 1999; 1999 to 2000; 2000 to 2001; and 2001 to 2002. The cohorts included all children enrolled in the public TennCare program — which includes Medicaid recipients and other low-income children — or three upstate New York private insurance plans — which cover 70% of children in the Rochester region. The Tennessee cohorts included more ethnic and racial minorities and children from low-income families.

The researchers compared the risk for frequent OM or pressure-equalizing tube insertion among the children from birth to age 5.

In New York, an average of 6,602 children were in each birth cohort, with a total of 26,409 children. Each Tennessee birth cohort included an average of 37,531 children, for a total of 150,122 children.

Children in the New York cohorts experienced reductions in frequent OM. Overall, 32% (n=2,656) of children had frequent OM. Thirty-eight percent of children in the 1998-1999 cohort had frequent OM by age 2, compared with 33% in the 1999-2000 cohort (Hazard Ratio=0.84 [95% CI, 0.79-0.89]), 29% in the 2000-2001 cohort (HR=0.72 [95% CI, 0.67-0.77]) and 27% in the 2001-2002 cohort (HR=0.67 [95% CI, 0.62-0.72]). The researchers noted a progressive decline ranging from 16% to 33%.

The researchers found that 1,121 children in the New York cohorts had pressure-equalizing tubes inserted by age 2. In the 1998-1999 cohort, 7.1% of the children had tubes inserted, compared with 6.3% in the 1999-2000 cohort (HR=0.87 [95% CI, 0.75-1.01]); 5.5% in the 2000-2001 cohort (HR=0.77 [95% CI, 0.65-0.90]); and 5.8% of children in the 2002-2002 cohort (HR=0.79 [95% CI, 0.67-0.94]).

In the Tennessee cohorts, 8,223 children received pressure-equalizing tubes by age 2, according to the researchers. They found that 7.1% of children in the 1998-1999 cohort had pressure-equalized tubes inserted, compared with 6.3% in the 1999-2000 cohort and 6.1% in the 2000-2001 cohort. However, it increased in the 2001-2002 cohort, back to 7.1% of children, the researchers wrote.

Twenty-six percent of children (n=39,763) in the Tennessee cohorts had frequent OM by age 2 overall. The researchers compared OM by cohort and found that 33% had frequent OM in the 1998-1999 cohort, compared with 29% in both the 1999-2000 (HR=0.84 [95% CI, 0.81-0.86]) and 2000-2001 cohorts (HR=0.83 [95% CI, 0.81-0.86]) and 31% in the 2001-2002 cohorts (HR=0.92 [95% CI, 0.89-0.94]).

Compared with the 1998-1999 cohort (HR=0.88 [95% CI, 0.82-0.93]), children experienced a reduction on frequent OM by age 2 of 16% for the 1999-2000 cohort, 17% for the 2000-2001 cohort (HR=0.84 [95% CI, 0.79-0.89]) and then 8% for the 2001-2002 cohort (HR=0.97 [95% CI, 0.92-1.03]), according to the researchers.

Increasing PCV7 coverage

Although the researchers did not know the vaccination status of the children studied, they used the National Immunization Survey (NIS) data to estimate the vaccination coverage with the pneumococcal conjugate vaccine (PCV7; Prevnar, Wyeth) for children in New York and Tennessee. The survey included only vaccination histories verified by providers in the analysis.

Less than 1% of children in the 1998-1999 birth cohort received at least three doses of the PCV7 vaccine in New York and Tennessee, compared with about 75% of children overall in the 2000-2001 birth cohorts, according to the researchers. In New York, vaccination increased from 0% to 82%, and to 73% in Tennessee.

The proportion of children who received four doses of vaccine also increased in both states to 53% of children in New York and 35% of children in Tennessee, according to the researchers.

Several factors likely contributed to the differences in frequent OM and pressure-equalizing tube procedures between the children in New York and the children in Tennessee. The New York cohorts had a higher uptake of PCV7 vaccination and a higher proportion of fully immunized children, according to the NIS data, the researchers wrote. Data suggest that mucosal antibody response develops 14 months after receiving the booster dose, which may affect OM protection.

The researchers also noted geographical differences. Physicians may use different criteria when diagnosing OM. In addition, data suggest that children in the South were more likely to have pressure-equalizing tubes inserted than children in the Northeast.

The researchers noted the reversing trend back toward baseline rates of frequent OM and pressure-equalizing tube insertion in the 2001-2002 Tennessee cohort. It is a “potentially important observation because the 2001-2002 cohort represents children with high PCV7 vaccination rates,” the researchers wrote.

The increase may be associated with an increase in nonvaccine serotypes, or increased use of medical care, which could increase the rate of OM–related medical visits even if the rate of disease was stable or reduced, according to the researchers.

The results suggest direct and indirect benefits of PCV7 vaccination, according to the researchers, and they suggested that further research is necessary to determine whether the trend of frequent OM and tube procedures will continue to decrease, as in the New York cohort, or wane, as in the Tennessee cohort.

For more information:

• Poehling KA, Szilagi PG, Grijalva CG, et al. Reduction of frequent otitis media and pressure-equalizing tube insertions in children after introduction of pneumococcal conjugate vaccine. Pediatrics. 2007;119:707-715.