National immunization coverage with 4:3:1:3:3 hits 81%

September 2005

The latest childhood immunization rate, released last month, shows more than 90% coverage for every childhood vaccine, except for two newer vaccines: pneumococcoal conjugate (PCV7; Prevnar, Wyeth) and varicella (Varivax, Merck).

Another milestone celebrated in a press conference in Washington was the news that 81% of the nation’s 19- to 35-month-old children received the recommended vaccine series 4:3:1:3:3 [four or more doses of diphtheria, tetanus and acellular pertussis (DTaP); three or more doses of poliovirus; one or more doses of a measles-containing vaccine; three or more doses of Haemophilus influenzae type b; and three or more doses of hepatitis B vaccine].

“One of the most important things or valuable things that parents can do to love their children and protect their children is to provide them with these life-saving immunizations,” said Stephen L. Cochi, MD, MPH, acting director of the National Immunization Program, during the press conference.

The new rates

The immunization rates were compiled from the 2004 National Immunization Survey (NIS). The CDC uses a quarterly random digit dialing sample of telephone numbers for each of the 78 survey areas to collect vaccination data for all age-eligible children. During 2004, the CDC obtained health care provider vaccination records for 21,998 children. The overall response rate for eligible households was 67.4%. The complete NIS data were released in the July 28 issue of the Morbidity and Mortality Weekly Report.

Although the coverage levels for varicella and pneumococcal conjugate (PCV7) vaccines did not exceed 90%, the report indicated a significant increase in the percentage of young children who received these newer vaccines. Because they were added recently to the routine childhood immunization schedule, they are not included in the overall series used to measure how well the country is immunizing its children. However, varicella vaccine will be included in the 2005 survey results for the overall series.

National coverage with varicella vaccine increased to 87.5% in 2004 from 84.8% in 2003. Coverage for three or more doses of PCV7 vaccine increased to 73.2% in 2004 from 68.1% in 2003. Coverage for doses of PCV7 increased to 43.4% compared with 35.8% in 2003, the first year the CDC measured coverage for the fourth dose.

The overall results indicated that the vaccination rate for the fourth dose of DTaP vaccine (85.5%) continued to lag behind other vaccines in the 4:3:1:3:3 series. As a result, the coverage estimates for the overall series is reduced.

The high immunization rates are an indication that temporary shortages of some routinely recommended childhood vaccines did not appear to affect vaccination coverage.

In 2004, as in previous years, there was substantial variation in coverage levels among states and among cities. Estimated coverage with the 4:3:1:3:3 series ranged from 89.1% in Massachusetts to 68.4% in Nevada. The range in coverage among the 28 urban areas was similar to the states. Among the 28 urban areas, the highest estimated coverage for the 4:3:1:3:3 series was 89.7% for Davidson County, Tenn., and the lowest was 64.8% for El Paso County, Texas.

No time to grow complacent

While coverage is up, and parents should be lauded for deciding to vaccinate their children, children still suffer from vaccine-preventable diseases, according to Cochi.

“The pertussis bacteria are brought back into the home by undervaccinated siblings [and] parents,” Cochi said, adding that “the same thing can happen with any of the other vaccine-preventable diseases.”

Some of the challenges ahead include establishing and maintaining a steady vaccine supply and introducing new vaccines and making them available. Another challenge is to reduce race and ethnic disparities in immunization. There is a 9% to 10% disparity between white and black children in coverage levels for completion of the 4:3:1:3:3 series.

“Unfounded fears” about vaccine safety must be addressed. “The amount of misinformation available from anti-vaccine groups is of epidemic proportions and needs to be addressed,” he said.

A recent example of false allegations is the unsupported claim, based on data from the California Department of Developmental Services, that the number of children receiving autism services from the state is now decreasing as a result of the removal of thimerosal from vaccines, according to Cochi. This is untrue, Cochi said. On the contrary, through the end of the second quarter of 2005, data actually show the number of children receiving state services is continuing to increase, suggesting the removal of thimerosal from routine childhood vaccines beginning in 1999 has had no effect on the incidence of autistic spectrum disorders.

Despite a slight increase in parental concerns about thimerosal and autism in recent surveys, according to Cochi, the immunization rate remains unaffected.

Adolescent challenges

Before announcing the new immunization rates, David A. Neumann, PhD, executive director of the National Partnership for Immunization, noted that while adolescent vaccination is going well, there remain challenges and barriers to immunize that population.

Twenty-five percent of U.S. adolescents lack at least one of the currently recommended vaccines, according to Neumann.

Some of the vaccine-preventable diseases, such as varicella and measles, are more severe in adolescent and adult populations than they are in children.

Each year, there are thousands of new hepatitis B infections among adolescents, Neumann noted, also citing the recent upsurge in adolescent pertussis cases.

“We are doing well with adolescent immunization, but we still have a way to go,” Neumann said.

For more information:

• CDC. National, state, and urban area vaccination coverage among children aged 19-35 months – United States, 2004. MMWR. 2005;54(29):717-721.