Rotavirus Vaccination Coverage and Adherence to the Advisory Committee on Immunization Practices (ACIP)-Recommended Vaccination Schedule --- United States, February 2006--May 2007

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Worldwide, rotavirus is the leading cause of severe gastroenteritis in children aged <5 years. In February 2006, a new human-bovine rotavirus vaccine, RotaTeq^® (Merck & Co., Inc., Whitehouse Station, New Jersey), was recommended by the Advisory Committee on Immunization Practices (ACIP) for routine vaccination of U.S. infants. Three doses of RotaTeq are recommended at ages 2, 4, and 6 months (1). The first dose should be administered between ages 6 and 12 weeks, and vaccination should not be initiated for infants aged >12 weeks. Subsequent doses should be administered at 4--10 week intervals, with all doses administered by age 32 weeks. This schedule is consistent with the ages at which RotaTeq was administered during prelicensure trials (1), and ACIP has recommended that RotaTeq only be administered at the ages for which safety and efficacy data are available. In 1999, a previous rhesus-human rotavirus vaccine, RotaShield^® (Wyeth Laboratories, Inc., Marietta, Pennsylvania), was withdrawn voluntarily from the U.S. market by the manufacturer because it was associated with intussusception, a form of bowel obstruction. The greatest risk for intussusception was noted after the first dose of RotaShield (2). Data from a large-scale, prelicensure safety trial and postlicensure monitoring do not indicate an association between the current RotaTeq vaccine and intussusception (3--5). CDC assessed rotavirus vaccination coverage among U.S. infants during February 2006--May 2007 and examined adherence to the ACIP-recommended vaccination schedule. This report summarizes the results of that assessment, which indicated that, by May 15, 2007, nearly half of infants aged 3 months had received 1 dose of rotavirus vaccine, with the majority of doses administered according to ACIP recommendations. Health-care providers should remain vigilant in following the ACIP-recommended vaccination schedule for rotavirus vaccine.

To assess rotavirus vaccination coverage and adherence to the vaccination schedule, CDC examined data from three data systems: 1) immunization information systems (IISs), 2) IIS sentinel sites, and 3) the Vaccine Safety Datalink (VSD). IIS data are derived from confidential, computerized records of vaccine administration collected from multiple health-care providers within a defined geographic area (e.g., a state or city). CDC funds the development and operations of IISs under the Public Health Service Act.* In 2006, approximately 65% of U.S. children aged <6 years participated in an IIS (6). IIS data were used to measure the number of rotavirus vaccine doses administered. Additional data were derived from the population-based IISs of Arizona, the District of Columbia, Michigan, Minnesota, Montana, and Oregon, which were participants in CDC's IIS sentinel site project during 2004--2007. Sentinel sites are a subset of the state IIS coverage area and represent >10,000 children aged <6 years in contiguous geographic counties, postal code areas, or U.S. Census tracts. These surveillance areas have high health-care provider participation and child enrollment (>90%) in the IIS. Procedures are in place in these sites to increase completeness and accuracy of the data (e.g., routine comparisons of IIS records with health-care provider data) (7). IIS sentinel site data were used to assess rotavirus vaccination coverage and adherence to the ACIP-recommended vaccination schedule.

VSD is a collaborative project involving CDC and eight medical-care organizations in the United States that collect data on approximately 5.5 million persons annually (8). VSD data provide comprehensive immunization histories and incorporate routine data-quality checks to promote data accuracy (9). VSD data were used to assess adherence to the ACIP-recommended vaccination schedule. For the assessment of adherence to the vaccination schedule, data on rotavirus vaccine administration by age (in weeks) and dose number in the series were reported by IIS sentinel sites through May 31, 2007, and by VSD through July 31, 2007. Some children might be enrolled in both IISs and VSD; however, this overlap is not anticipated to affect the estimates of adherence in either system, which were analyzed separately. In both systems, the date of vaccine administration was used to determine the dose number in the series, with the first date of vaccine administration counting as dose 1.

During February 2006--May 2007, a total of 1,120,239 administered doses that were recorded by IISs in 27 states reporting rotavirus vaccine administration by dose number in the series. The monthly number of doses administered increased from approximately 4,000 doses in May 2006 to nearly 134,000 in March 2007. At the six IIS sentinel sites, vaccination coverage increased from the third quarter of 2006 to the second quarter of 2007 (Figure 1). As of May 15, 2007, 1-dose rotavirus vaccination coverage among infants aged 3 months at IIS sentinel sites ranged from 40.1% to 65.4% (mean: 49.1%). Rotavirus vaccination coverage estimates were compared with coverage estimates of other infant vaccines. At IIS sentinel sites, 1-dose coverage at age 3 months ranged from 69.3% to 90.4% (mean: 84.1%) for pneumococcal conjugate vaccine (PCV7) and from 69.5% to 92.3% (mean: 85.7%) for diphtheria, tetanus, and acellular pertussis (DTaP) vaccine.

A total of 107,128 doses were reported by IIS sentinel sites, and 90,151 doses were reported by VSD (Table). At IIS sentinel sites, 45,659 (85.9%) of 53,143 first doses were administered within the recommended age range of 6--12 weeks, whereas in VSD, 38,582 (92.8%) of 41,583 first doses were administered within the recommended age range (Figure 2). For the respective 7,484 (14.1%) and 3,001 (7.2%) first doses administered outside the recommended age range, small peaks were observed at ages 17 and 26 weeks. When analysis of IIS sentinel site and VSD data was restricted to infants who received >3 doses, 21,395 (95.0%) of 22,526 first doses at IIS sentinel sites and 25,629 (98.6%) of 26,005 first doses in VSD were administered within the recommended age range. Small peaks in administration of the first dose were noted at age 17 weeks in both data sources.

A small percentage of doses were reported as administered completely outside the recommended age range of 6--32 weeks. Of all doses reported by IISs, IIS sentinel sites, and VSD, 0.1%, 0.2%, and 0.04%, respectively, were administered at age <6 weeks, and 1.8%, 1.6%, and 0.7%, respectively, were administered at age >32 weeks.

Reported by: HA Clayton, MPH, MM Cortese, MD, DC Payne, PhD, DL Bartlett, MPH, LA Zimmerman, MPH, WG Williams, MPH, M Wang, MPH, LJ Stockman, MPH, U Parashar, MBBS, National Center for Immunization and Respiratory Diseases; J Baggs, PhD, Immunization Safety Office, Office of the Chief Science Officer, CDC.

Editorial Note:

Routine vaccination of infants with rotavirus vaccine is anticipated to be the most effective public health intervention for reducing the substantial burden of rotavirus disease in children. Rotavirus vaccination coverage in the United States increased during the year after the February 2006 ACIP recommendation, and by May 2007, nearly half of infants aged 3 months in IIS sentinel sites had received 1 dose of rotavirus vaccine. Although the majority of health-care providers in these systems appear to be administering the vaccine as recommended, the findings in this report suggest that some infants are receiving their first dose of rotavirus vaccine outside of the ACIP-recommended schedule.

The findings in this report are subject to at least three limitations. First, in each data source, the date of vaccine administration was used to determine the dose number in the series, with the first date of vaccine administration counted as dose 1. Thus, doses counted as first doses but administered at approximately ages 17 and 26 weeks (i.e., the ages when second and third doses of vaccine are recommended) might actually represent second or third doses for infants whose previous doses were not recorded in these systems. Alternatively, the late first doses might represent infants receiving rotavirus vaccine during routine well-child visits at ages 4 and 6 months. To explore these hypotheses, analysis of IIS sentinel site and VSD data was restricted to infants who received >3 doses (i.e., infants who were more likely to have a first dose recorded); that analysis determined that a lower percentage of first doses were administered outside the recommended age range. However, small peaks in administration of first doses were still noted at age 17 weeks in both data sources, indicating that some children received rotavirus vaccine outside of the recommended schedule. The decrease in the percentage of first doses administered outside of the schedule might be attributable, in part, to the possibility that infants who receive all 3 doses are more likely to be vaccinated on schedule than other infants. Second, although IIS sentinel site and VSD data are monitored for accuracy and completeness, some vaccinations might not be entered into a child's electronic record, potentially resulting in an underestimation of vaccination coverage levels (10). Finally, the populations captured in IIS sentinel sites and VSD might not be nationally representative, which might limit the generalizability of these findings. The National Immunization Survey (NIS) provides childhood vaccination coverage data that are nationally representative. However, because the survey targets children aged 19--35 months, NIS data on rotavirus vaccination coverage will not be available until 2009 or 2010, nearly 2 to 3 years after the February 2006 ACIP recommendation for rotavirus vaccination.

Although these initial findings on rotavirus vaccination coverage are encouraging, public health professionals should continue to monitor vaccination coverage, identify potential barriers to vaccination, and increase vaccination coverage to levels similar to those for other recommended infant vaccines. In addition, health-care providers should remain vigilant in following the ACIP-recommended vaccination schedule for rotavirus vaccine and are reminded to report any adverse events to the Vaccine Adverse Events Reporting System.

The findings in this report are based, in part, on contributions by R Volp, Arizona Dept of Health Svcs; RP McLaren, MS, District of Columbia Dept of Health; KS Enger, MPH, Michigan Dept of Community Health; K White, MPH, Minnesota Dept of Health; B Wehner, Montana Dept of Public Health and Human Svcs; J Gaudino, MD, Oregon Dept of Human Svcs; and E Belongia, MD, Vaccine Safety Datalink, CDC.

References

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