New observational study suggests use of combination vaccines may improve immunization coverage rates in infants

Data presented for the first time at the 40th National Immunization Conference

Atlanta, GA (March 8, 2006) ˇV Results from a new observational study of administrative claims data from the Georgia State Medicaid program showed that infants who received a combination vaccine had higher immunization coverage rates in the first two years of life compared to infants given component vaccines. Results from the study were presented today at the Centers for Disease Control and Prevention's 40th National Immunization Conference (NIC) in Atlanta, GA, by Gary S. Marshall, M.D., Professor of Pediatrics at University of Louisville, Louisville, KY. The study was conducted by Dr. Marshall in collaboration with Applied Health Outcomes of Palm Harbor, Florida.

The study evaluated the immunization history of infants born between January and September 2003, with continuous enrollment in the Georgia Medicaid Program for at least 24 months following birth, identified from administrative claims of the Georgia Department of Community Health. Infants who were eligible for the study were distributed into two cohorts. The combination group (N=1990) was made up of those infants who received at least one dose of PEDIARIX„µ [Diphtheria and Tetanus Toxoids and Acellular Pertussis Adsorbed (DTaP), Hepatitis B (Recombinant, HepB) and Inactivated Poliovirus Vaccine (IPV) Combined] and the component group (N=1990) consisted of those who were immunized with separate injections of DTaP, HepB and IPV or alternate combinations (DTaP-Hib or HepB-Hib)]. Each infant in the combination vaccine group was matched by gender and birth date to an infant in the component vaccine group. Immunization coverage rates were evaluated at 24 months of age by comparing the status of actual vaccinations administered according to the ACIP/AAP/AAFP recommended immunization schedule.

Results from the analysis showed that the combination cohort had significantly higher coverage rates than the component cohort for 4 doses of diphtheria, tetanus and pertussis (DTaP) vaccine (58.0 percent vs. 43.5 percent; p<0.001); 3 doses of polio vaccine (71.9 percent vs. 49.6 percent; p<0.001); and 3 doses of hepatitis B vaccine (49.6 percent vs. 22.0 percent; p<0.001). In addition, higher coverage rates were also seen for the combination cohort compared to the component cohort for certain vaccines given in the second year of life: measles, mumps and rubella vaccine (MMR) (86.1 percent vs. 81.4 percent; p<0.001); varicella vaccine (86.1 percent vs. 81.4 percent; p<0.001); and Haemophilus influenzae type b (Hib) (71.7 percent vs. 55.9 percent; p<0.001). Coverage rates were also higher in the combination cohort compared to the component cohort for the 4:3:1:3:3:1 series combination (includes 4 doses of DTaP, 3 doses of polio, 1 dose of MMR, 3 doses of Hib, 3 doses of hepatitis B, and 1 dose of varicella vaccine (34.3 percent vs. 14.9 percent; p<0.001).

ˇ§Results from this study suggest that incorporation of a combination vaccine into the routine immunization schedule for the first year of life may yield improved coverage rates,ˇ¨ said Dr. Marshall. ˇ§As suggested by improved coverage rates for the varicella and MMR vaccines, the effect might not be limited to the antigens contained in the combination vaccine. Overall, these results suggest that further research is warranted to determine the full impact of combination vaccines on the quality of immunization care.ˇ¨

Two additional observational studies of the Georgia Medicaid population, conducted by Dr. Marshall in collaboration with Applied Health Outcomes, were also presented at NIC today. The first assessed the impact of PEDIARIX on immunization timeliness in the same cohorts to determine if the infants studied received their vaccinations on time, based on the ACIP/AAFP/AAP recommended immunization schedule, or acceptably early as defined by Luman, et al in a previous study sponsored by the Centers for Disease Control and Prevention (CDC)*.

Results from the analysis showed that mean delays in vaccination were significantly shorter (p<0.01) in the combination cohort for the immunization series of the antigens contained in PEDIARIX. Children in the combination cohort had a mean delay of 245 days in receiving 4 DTaP vaccinations, 213 days in receiving 3 hepatitis B vaccinations, and 139 days in receiving 3 polio vaccinations, compared to respective delays of 317 days, 363 days and 252 days in the component cohort (p<0.001 for each comparison). There were significantly greater percentages of children in the combination cohort judged to be on time for receipt of the polio, hepatitis B, and varicella vaccination series as well as a significant increase in the percentage of children on time for all vaccinations (10.1 percent in the combination group vs. 6.8 percent in the component group, p<0.001). In addition, significantly more children in the component cohort had cumulative delays of greater than six months compared to those in the PEDIARIX cohort (78.7 percent vs. 67.2 percent, respectively; p<0.0001). When assessing children in both cohorts considered covered at 24 months by traditional measures, 44.0 percent, 55.1 percent and 18.1 percent of children had delays for DTaP, hepatitis B and polio, respectively. Delays in the same vaccinations were also observed in the CDC-sponsored study*, which was based on the National Immunization Survey. While overall the on-time rates favored the combination cohort, this analysis did not find a significant difference for on-time receipt of DTaP, Hib, or MMR for the two cohorts.

*Luman ET, et al. Timeliness of Childhood Vaccinations in the United States, JAMA. 2005;293:1204-1211

The second analysis of both cohorts assessed the impact of on-time (according to the ACIP/AAFP/AAP definition of age-appropriate vaccination) first, second and third DTaP doses (first year primary series) on the timeliness of the fourth dose of DTaP (second year booster dose). Of the children previously identified, 36.0 percent were on time and 64.0 percent had delayed first year shots. Further analysis showed that children with DTaP delays in their first year were significantly less likely to be on time for their second year DTaP compared to children who had on-time first year DTaP (18.3 percent vs. 78.9 percent, respectively, p<0.0001).

ˇ§Despite record high immunization levels, many children in the U.S. are not immunized on time,ˇ¨ said Dr. Marshall. ˇ§These analyses suggest the importance of adhering to the recommended timeline for primary series vaccinations. This can increase the likelihood that future immunizations remain on schedule and might help to decrease the risk of vaccine-preventable diseases like pertussis.ˇ¨


GlaxoSmithKline provided financial support for these observational studies.

PEDIARIX is indicated for active immunization against diphtheria, tetanus, pertussis (whooping cough), all known subtypes of hepatitis B virus, and poliomyelitis caused by poliovirus Types 1, 2, and 3 as a three-dose primary series in infants born of HBsAg-negative mothers, beginning as early as 6 weeks of age. PEDIARIX should not be administered to any infant before the age of 6 weeks, or to individuals 7 years of age or older. PEDIARIX has been marketed in the United States since 2003.

PEDIARIX has been proven safe and effective in numerous clinical trials, where 20,739 doses of PEDIARIX were administered to 7,028 infants. In clinical studies, adverse events in infants receiving PEDIARIX included injection-site reactions (pain, redness, or swelling), fever, and fussiness. Administration of PEDIARIX was associated with higher rates of fever relative to separately administered vaccines (see Adverse Reactions section of the package insert). PEDIARIX is contraindicated in infants with known hypersensitivity to any component of the vaccine including yeast, neomycin, and polymyxin-B. As with any vaccine, vaccination with PEDIARIX may not protect 100% of susceptible individuals.

PEDIARIX is manufactured by GlaxoSmithKline Biologicals, Rixensart, Belgium and distributed by GlaxoSmithKline.

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Last reviewed: By John M. Grohol, Psy.D. on 21 Feb 2009
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