Published Online: December 17, 2012
Bradley K. Ackerson, MD; Lina S. Sy, MPH; Janis F. Yao, MS; Craig T. Cheetham, PharmD, MS; and Steven J. Jacobsen, MD, PhD
Objective: To assess the impact of using the combined measles, mumps, rubella, and varicella vaccine (MMRV) instead of the measles, mumps, and rubella vaccine and the varicella vaccine separately (MMR+V) on uptake of vaccines recommended by the Advisory Committee for Immunization Practices (ACIP) in young children.
Study Design: Retrospective cohort study.
Methods: Electronic immunization records of children 12 to 15 months of age who received either MMR+V (n = 29,716) or MMRV (n = 29,711) between November 2003 and June 2007 while enrolled in Kaiser Permanente Southern California were evaluated. Proportions of children who received either MMRV or MMR+V and other ACIP-recommended vaccines either simultaneously or during recommended age intervals were compared.
Results: Concomitant administration of DTaP (76.3 vs 75.6%), PCV7 (89.1 vs 78.6%), Hib (92.3 vs 91.3%), and hepatitis A vaccine (HAV) (44.2 vs 0.1%) and on-time administration of PCV7 (91.7 vs 78.7%), Hib (93.9 vs 93.2%), and HAV (86.8 vs 24.3%) were greater with MMRV than with MMR+V. On-time administration of DTaP (91.4 vs 90.5%) and IPV (91.3 vs 90.0%) was greater with MMR+V than with MMRV.
Conclusions: Concomitant and on-time administration of most ACIP-recommended vaccines was greater with MMRV than with MMR+V despite the addition of HAV to the recommended schedule after introduction of MMRV. However, the modest compliance increases suggest that focusing on other barriers to compliance may be important to increasing adherence to future vaccination recommendations.
(Am J Manag Care. 2012;18(12):e440-e445)
Vaccination compliance improved slightly following the introduction of MMRV combination vaccine in place of the MMR and varicella vaccines given separately.
This increase was detected in spite of addition of another vaccine to the immunization schedule at the same time that MMRV was introduced.
The increase in compliance was small, suggesting that other barriers to vaccination compliance may need to be addressed in order to optimize adherence to future vaccinationrecommendations.
Combination vaccines will continue to be important to maintaining vaccine complianceas new vaccines are added to the recommended immunization schedule.
Childhood immunizations have markedly reduced an increasing number of vaccine-preventable diseases.1 However, vaccination rates among children remain less than optimal, with nearly 30% of children failing to receive all recommended vaccines by 2 years of age2 and as many as 90% of children failing to receive all recommended doses at age-appropriate intervals.3
In an attempt to improve childhood vaccination coverage rates, the standards for pediatric immunization practices direct providers to administer simultaneously all vaccines for which children are eligible at each visit.4 However, concerns of parents and providers about the pain and psychological trauma associated with the administration of multiple injections result in a reluctance to administer more than 2 to 3 injections simultaneously.5-7 This frequently results in vaccine deferral,8,9 which substantially reduces vaccine coverage rates.10-14 The importance of simultaneous administration of vaccines will grow as the number of vaccines included in the childhood vaccine schedule increases. Between 1991 and 2000, the number of injections necessary to provide all recommended vaccinations for children through age 23 months increased from 11 to 17, assuming the use of all combination vaccines then licensed in the United States.15,16 However, development of combination vaccines may decrease the number of injections required to provide the increasing number of recommended vaccines, potentially improving immunization rates.
ProQuad (MMRV; Merck and Co, Inc, Summit, New Jersey), a combination of measles, mumps, and rubella (MMR) and varicella vaccines, was developed primarily to increase varicella vaccine coverage in children. However, we hypothesized that decreasing the number of injections required for children at 12 to 15 months of age, when the recommended vaccination schedule is particularly injection dense,17 might increase the simultaneous uptake of other childhood vaccines recommended by the Advisory Committee for Immunization Practices (ACIP). The objective of this study was to assess the impact of combining the MMR and varicella vaccines on the uptake of other vaccines given at the same time as MMRV or the MMR vaccine and varicella vaccine separately (MMR+V) in children 12 to 15 months of age.
Subjects for this study had been included in a phase-IV post-licensure retrospective cohort study that was conducted by Kaiser Permanente Southern California (KPSC) to evaluate the safety of a combined MMRV vaccine licensed in the United States in 2005 as previously described.18 Briefly, children 12 to 60 months of age who received a first dose of MMRV between February 2006 and June 2007 or MMR+V between November 2003 and January 2006 in KPSC were included in the study. Subjects who received MMRV were optimally matched without replacement on age, sex, and month and day of vaccination to children who received MMR+V. Children were excluded if they had a history of measles, mumps, rubella, or varicella disease, or a history of vaccination for any of these diseases. To allow validation of these criteria, subjects were required to be continuously enrolled in the Kaiser Foundation Health Plan from age 6 months until 90 days following vaccination. We compared the proportions of children aged 12 to 15 months who received either MMRV or MMR+V and the vaccinations recommended in the routine childhood vaccination schedule19 either simultaneously (concomitantly) or during recommended age intervals (on time). Study subjects were members of KPSC, the largest managed care organization in Southern California, serving 3.4 million members who are broadly representative of the diverse racial, ethnic, and socioeconomic background of the source population in Southern California. Vaccinations may be administered to members without charge at any visit including no-cost nurse visits. Immunizations are tracked by KPSC through the Kaiser Immunization Tracking System, one of the largest immunization tracking systems in the United States.
Several changes in the schedule of recommended childhood vaccines occurred during the study that affected measurements of compliance with vaccination recommendations (Figure). Due to a nationwide shortage of pneumococcal conjugate vaccine (PCV7), the fourth and the third PCV7 doses were suspended for low-risk children in February 2004 and March 2004, respectively; as the shortage resolved, these doses were reinstituted in July 2004 and September 2004, respectively.20-23 Therefore, compliance with recommendations to administer PCV7 dose 4 in the MMR+V recipients was corrected by excluding children who received MMR+V between February 2004 and September 2004 when PCV7 dose 4 was suspended.20,23 The recommendation to administer hepatitis A vaccine (HAV) at 12 months of age was made in January 200624 just prior to introduction of MMRV at KPSC on February 1, 2006.
In order to estimate the impact of combining MMR and varicella vaccines on varicella vaccine uptake and to estimate the relative compliance of the source population for each cohort, we compared the uptake of MMRV with the uptake of MMR+V in 1-year samples of children drawn from the source population from which the cohorts were drawn for the phase-IV postlicensure study described previously.18 Vaccinated children were required to have had continuous membership from 6 months of age to the time of vaccination. The percentage of children born between March 1, 2005, and February 28, 2006, who received the first dose of MMRV at age 12 to 15 months was compared with the percentage of children born between March 1, 2003, and February 28, 2004, who received the first dose of MMR+V at age 12 to 15 months.
Race and ethnicity data were available from health plan files for 82% of members included in this study and were complete for 90% after surname analysis and geocoding imputation.25
Chi-square tests were used to compare the percentages. All tests were conducted using SAS software (SAS Enterprise Guide, version 4.1, SAS Institute Inc, Cary, North Carolina). This study was approved by the KPSC Institutional Review Board.
Of the 31,298 children each in the MMRV and MMR+V cohorts,18 29,711 and 29,716 were between 12 to 15 months of age, respectively. The demographics of the cohorts were similar (Table 1).
Compliance Among MMRV and MMR+V Recipients
The on-time and concomitant uptake of recommended childhood vaccines among children who received MMRV or MMR+V between 12 and 15 months of age is shown in Table 2. Concomitant administration of the booster doses of diphtheria, tetanus, and pertussis (DTaP), PCV7, and Haemophilus influenzae b (Hib) was greater with MMRV than with MMR+V (P <.001 to P <.04). However, most differences were small (0.7%-10.5%). Concomitant administration of inactivated polio vaccine (IPV) dose 3 was low for MMRV and MMR+V (1.83%-1.92%). Similarly, on-time administration of booster doses of PCV7 and Hib vaccines was greater with MMRV than with MMR+V, though the differences were small (0.7%-13.0%). On the other hand, on-time administration of DTaP booster and IPV dose 3 was greater with MMR+V than MMRV (P <.001), but the differences were small (0.8%- 1.3%). The hepatitis A vaccine was given more often both concomitantly and on-time with MMRV than with MMR+V (P <.001).
Combined on-time administration of all recommended vaccines (DTaP, PCV7, Hib, and IPV) was greater with use of MMRV than with MMR+V. This result held both with inclusion and exclusion of HAV from analysis (64.6% vs 18.5% and 74.1% vs 60.5%, respectively; both P <.001).
Uptake of MMRV vs MMR+V in Young Children
In 1-year samples of children from the cohort source populations, 81.4% of children who were born between March 1, 2005, and February 28, 2006, received MMRV at 12 to 15 months of age and 81.7% of children born between March 1, 2003, and February 28, 2004, received MMR+V at 12 to 15 months of age (P = .26) (Table 3).
The recommended vaccine schedule has become increasingly injection dense, particularly at the 1-year visit. Strategies to address this situation have included giving vaccines at other ages and developing combination vaccines. However, many vaccines cannot be given at less than 12 months of age due to diminished efficacy.26 In addition, deferring vaccination results in decreased uptake.10-14,27,28 Combination vaccines make it possible to administer vaccines on schedule while reducing the number of injections given to patients.18,29 In this study, we evaluated the potential effect of combining MMR and varicella vaccines on the uptake of other recommended vaccines in children 12 to 15 months of age. While an increase was seen in the combined uptake of vaccines given concomitantly as well as on time with MMRV compared with MMR+V, the statistically significant but small increase in uptake of individual vaccines noted in this study is likely of limited clinical significance.
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