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Use of a Data-Based Approach by a Health Maintenance Organization to Identify and Address Physician Barriers to Pediatric Vaccination California, 1995

Based on a vaccination coverage assessment during January-May 1994, 44% of 2-year-olds enrolled in the southern California health plan of a national health maintenance organization (HMO) were up-to-date at their second birthday for the complete series of recommended vaccinations (4:3:1:1 series *). This coverage level was low compared with the levels for some other health plans in the HMO (range: 39%-85% for the 41 other health plans). The assessment had been recommended by the National Committee for Quality Assurance (a national accreditation body for HMOs), and data had been obtained for analysis from the 1993 Health Plan Employer Data and Information Set (HEDIS), which is a standardized set of health-plan performance measurements including selected preventive services (e.g., mammography, cervical cancer screening, eye examinations for persons with diabetes, cholesterol screening, and pediatric vaccination) (1). To assist the southern California health plan in developing interventions for increasing coverage, in May 1995, the HMO's national research center conducted a study to determine possible causes for the low pediatric vaccination coverage level. This report summarizes the findings of the analysis and illustrates the use of a data-based approach to assist in solving problems related to low vaccination coverage in a managed-care setting.

The setting is a non-Medicaid, independent practice association (IPA) model health plan with approximately 150,000 members and 4300 affiliated primary-care physicians in southern California. To verify the 44% vaccination rate, investigators at the research center reviewed the full texts of medical charts of a subset of children that had been previously identified in the 1993 HEDIS sample as members of the health plan. In 1993, a total of 1396 children aged 2 years were enrolled in the plan; of these, 255 (18%) met the HEDIS eligibility criteria of continuous enrollment since age 42 days. A simple random sample of 137 children was then selected from the 255 eligible children to comprise the 1993 HEDIS sample; of these, medical charts were available for 107 children at the time of the reassessment in 1995. Charts were unavailable for 30 children: 12 children were no longer enrolled in the plan, and the primary-care physicians for 18 enrolled children refused to release their charts. The 107 children were born in 1991 and had been continuously enrolled in the health plan from at least age 42 days to 24 months.

Vaccination dates were abstracted from charts and entered into the Clinical Assessment Software Application developed by CDC (2). To assess physician knowledge, attitudes, and practices regarding pediatric vaccination, a survey was mailed to the 97 physicians providing care for the children in the sample. The survey contained items adapted from instruments previously used to identify physician barriers to pediatric vaccination (3,4). Standard reports produced by CASA were used to calculate vaccination rates and estimate missed opportunities for simultaneous vaccinations.

Assessment of Pediatric Vaccination Coverage

Based on the medical chart review of the 107 children, 47 (44%) were up-to-date with all recommended vaccinations by age 24 months (Table_1). An estimated 23% of vaccination visits involved a missed opportunity to administer more than one vaccine. Eliminating these missed opportunities would have increased the overall vaccination coverage level to 55%.

Of the 76 (71%) children who had received their first vaccine by age 3 months, 54 (71%) were up-to-date with the 4:3:1 vaccination series ** by age 24 months. In contrast, of the 31 children who did not receive their first vaccine by age 3 months, two (6%) were up-to-date by age 24 months.

Physician Knowledge, Attitudes, and Practices

Of the 97 physicians surveyed, four were excluded because they did not provide well-child care; 71 (76%) of the remaining 93 physicians returned a questionnaire. Respondents reported their practices to include vaccinating children during acute-care visits (85%) and follow-up visits (97%); simultaneously administering four vaccines *** to an eligible 18-month-old child (94%); and referring some children to other physicians/facilities for vaccinations (15%) (Table_2). Invalid contraindications also were assessed, and 61% of respondents reported not administering diphtheria and tetanus toxoids and pertussis vaccine when a child has a low-grade fever (less than 102.2 F {less than 39.0 C}) or when a child has afebrile bronchiolitis ****. Reported barriers to vaccinations included lack of a system to track undervaccinated children (37%) and temporary interruptions in the supply of some vaccines during the 12 months preceding the survey (18%). In addition, 39% of respondents offered no suggestion for improving vaccination rates in their practices.


These findings were presented to the southern California health plan's management during a workshop to facilitate the design and implementation of data-based interventions. Participants worked in groups to examine the importance of each barrier and address options for the health plan to reduce or eliminate the barrier. After priorities were established, participants specified the behaviors, interventions, and methods to eliminate the barriers. Following the workshop, the health plan's management 1) disseminated CDC's Guide to Contraindications to Childhood Vaccinations to all pediatricians affiliated with the health plan, 2) conducted sessions to educate physicians about valid contraindications to vaccination, and 3) developed a plan to capture updated member addresses and telephone numbers to enhance vaccination-reminder and recall efforts. The results of the 1995 HEDIS assessment will assist the research center and the health plan in determining whether these interventions increased the previously documented vaccination coverage level.

Reported by: CA McPhillips-Tangum, MPH, NA Lewis, MPH, C Ward-Coleman, JP Koplan, MD, The Prudential Center for Health Care Research, Atlanta, Georgia. P Lee, E Batchlor, MD, IJ Kamil, MD, The Prudential Health Care System, Woodland Hills, California; A Small, MD, The Prudential Health Care System, Roseland, New Jersey. National Immunization Program, CDC.

Editorial Note

Editorial Note: The population-based and data-based approaches described in this report are common features of public health programs and, as illustrated in this report, can be implemented in managed-care delivery systems. In particular, the HEDIS health-plan performance measures that prompted the southern California health plan to review its vaccination activities underscore the capacity of managed-care organizations to collect and use data for improving prevention efforts. Physician behavior to improve vaccination coverage may be influenced more readily in HMOs with centralized facilities and unique providers (e.g., group- or staff-model HMOs) than in IPA models, which comprise a network of independent physicians who serve a small proportion of the patient population in a particular HMO (5).

An important barrier to pediatric vaccination for many physicians in the health plan in southern California is the lack of systems to identify and track undervaccinated children. Provider-based tracking systems are well suited to both group- and IPA-model HMOs, and previous studies document their effectiveness in increasing vaccination coverage (6).

The findings in this report are subject to at least two limitations. First, the HEDIS measures used by HMOs -- and consequently the measures used in this survey -- require that children be continuously enrolled in the HMO since age 42 days to be eligible for inclusion in the HEDIS sample. In 20 of the health plans in the national HMO, the percentage of children who meet this criterion ranges from 16% to 87%; however, in the health plan described in this report, the criterion limited eligibility to only 18% of enrolled children. Consequently, these findings may not be generalizable to the total population of 2-year-olds enrolled in the health plan. For example, children continuously enrolled since age 42 days probably had more health-care visits and consequently more opportunities to be vaccinated than those enrolled for less time, and vaccination coverage for the continuously enrolled children may overestimate the coverage in the total population of 2-year-olds enrolled in the plan. In contrast, because some children may have received vaccinations from providers outside the health plan, and such information is not included in the plan's database, coverage for the children in this sample may underestimate true coverage. Second, these data included children born during January-December 1991 who were aged 24-35 months during the 1993 HEDIS report period for which data were collected in 1994 and were reexamined in 1995 for this report. Recently released national estimates for children who were born during May 1991-August 1993 documented series-complete coverage of 72% (7). Because of interventions initiated during 1991-1996 to increase coverage nationwide, current rates in this health plan may be greater than 44% for children who were born after 1991 (7). Moreover, the mean HEDIS vaccination rate for all the health plans in the national HMO was 66% in 1994, even before the interventions described in this report were initiated in southern California.

The efforts of approximately 300 HMOs nationally are part of the Childhood Immunization Program led by the American Association of Health Plans (formerly Group Health Association of America and the American Managed Care and Review Association) to increase vaccination coverage levels and reach the national target of 90% vaccination coverage. Several managed-care organizations, including an IPA model, have successfully increased vaccination coverage at least 30 percentage points using data-based approaches as part of their quality-improvement activities (8); similar efforts in the public sector have improved vaccination levels in Georgia (8) and are being implemented in other states. More widespread adoption of these population-based and data-based techniques in both the public and private sectors can assist in accelerating the achievement of national vaccination coverage goals.


  1. National Committee for Quality Assurance. Health Plan Employer Data and Information Set (HEDIS) (version 2.0). Washington, DC: National Committee for Quality Assurance, 1993.

  2. CDC. Clinic Assessment Software Application (CASA) user's guide, version 3.0. Atlanta, Georgia: US Department of Health and Human Services, Public Health Service, CDC, 1994.

  3. Szilagyi PG, Rodewald LE, Humiston SG, et al. Immunization practices of pediatricians and family physicians in the United States. Pediatrics 1994;94:517-23.

  4. Lieu TA, Black SB, Ray P, et al. Risk factors for delayed immunization among children in an HMO. Am J Public Health 1994;84:1621-5.

  5. Shenkin BN. The independent practice associated in theory and practice. JAMA 1995;273:1937-42.

  6. Abramson JS, O'Shea TM, Ratledge DL, Lawless MR, Givner LB. Development of a vaccine tracking system to improve the rate of age appropriate primary immunization in children of lower socioeconomic status. J Pediatr 1995;126:583-6.

  7. CDC. National, state, and urban area vaccination coverage levels among children aged 19-35 months -- United States, April 1994-March 1995. MMWR 1996;45:145-50.

  8. CDC. Evaluation of vaccination strategies in public clinics -- Georgia, 1985-1993. MMWR 1995; 44:323-5.

Four doses of diphtheria and tetanus toxoids and pertussis vaccine (DTP), three doses of oral poliovirus vaccine (OPV), one dose of measles-mumps- rubella vaccine (MMR), and one dose of Haemophilus influenzae type b vaccine (Hib) (after age 12 months). ** Four doses of DTP, three doses of OPV, and one dose of MMR. *** DTP, OPV, MMR, and Hib. **** Low-grade fever and afebrile bronchiolitis are not intrinsic contraindications; however, the clinical condition of the patient must be considered by the health-care professional when administering vaccine and occasionally may warrant withholding vaccine.

Note: To print large tables and graphs users may have to change their printer settings to landscape and use a small font size.

TABLE 1. Number of children * enrolled in an HMO + health plan who were
up-to-date for recommended vaccinations, by vaccination status and age --
California, 1995
                            By age 24 months
Vaccination status    No.                     (%)
4:3:1:1 series &      47                     (44%)
Four DTP              65                     (61%)
Three OPV             71                     (66%)
One MMR               76                     (71%)
One Hib               66                     (62%)
* n=107.
+ Health maintenance organization.
& Four doses of diphtheria and tetanus toxoids and pertussis vaccine (DTP),
  three doses of oral poliovirus vaccine (OPV), one dose of measles-mumps-
  rubella vaccine (MMR), and one dose of Haemophilus influenzae type b
  vaccine (Hib) (after age 12 months).

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Note: To print large tables and graphs users may have to change their printer settings to landscape and use a small font size.

TABLE 2. Number and percentage of physicians * in an HMO + health plan, by
selected characteristics -- California, 1995
Physician characteristic                     No.  (%)
Would vaccinate during visit(s) for:
 Acute care                                  60   (85)
 Follow-up care                              69   (97)

Had mechanism to identify
 undervaccinated children
 No specific system                          26   (37)
 Computer tracking system                     6   ( 8)
 "Tickler system" (i.e., index cards)         7   (10)
 Systematic chart reviews                    29   (41)
 Other                                       10   (14)

Would give DTP, OPV, MMR, and Hib &
 at a single preventive-care visit           67   (94)

Reported vaccines unavailable
 during preceding year                       13   (18)

Ever referred patients elsewhere
 for vaccination(s)                          11   (15)

Would not administer DTP
 to an 18-month-old child
 with the following invalid
 Gastroenteritis (no dehydration)            27   (38)
 Otitis media (afebrile)                     22   (31)
 Upper respiratory infection (afebrile)       7   (10)
 Bronchiolitis @ (afebrile)                  43   (61)
 Fever @ (<102.2 F {<39.0 C})                43   (61)

Would not administer MMR
 to an 18-month-old child
 with the following invalid
 Gastroenteritis (no dehydration)            24   (34)
 Otitis media (afebrile)                     19   (27)
 Upper respiratory infection (afebrile)       6   ( 8)
 Bronchiolitis @ (afebrile)                  41   (58)
 Fever @ (<102.2 F {<39.0 C})                42   (59)
* n=71.
+ Health maintenance organization.
& Diphtheria and tetanus toxoids and pertussis vaccine, oral poliovirus
  vaccine, measles-mumps-rubella vaccine, and Haemophilus influenzae type
  b vaccine.
@ These conditions are not intrinsic contraindications; however, the
  clinical condition of the patient must be considered by the health-care
  professional when administering vaccine and occasionally may warrant
  witholding vaccine.

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