Compliance with national immunization guidelines for children younger than 2 years, 1996-1999.
OBJECTIVE
To evaluate compliance with national immunization guidelines among a large cohort of children cared for at health maintenance organizations (HMOs) and to examine effects on immunization status.


METHODS
A cohort study of 176134 children born between January 1, 1994, and December 31, 1997, and monitored from birth to the second birthday was performed. Subjects belonged to the Vaccine Safety Datalink Project, a study of children enrolled in 1 of 4 HMOs. Children were continuously enrolled in a HMO for the first 2 years of life. Prevailing recommendations regarding optimal ages of immunization and intervals between doses were applied to define appropriate immunization timing and immunization status. Noncompliance was defined as having a missing or late immunization or an immunization error. Immunization errors included invalid immunizations (too early to be acceptable), extra immunizations (superfluous immunizations or make-up immunizations for invalid immunizations), and missed opportunities resulting in late or missing immunizations.


RESULTS
Although 75.4% of children in these HMOs were up to date for all immunizations at 2 years, only 35.6% of children were fully compliant with recommended immunization practices. Less than 8% of children received all immunizations in accordance with strict interpretation of recommended guidelines. Fifty-one percent of children had at least 1 immunization error by age 2 years; 29.7% had a missed opportunity with subsequent late or missing immunization, 20.4% had an invalid immunization, and 11.6% had an extra immunization. Common reasons for noncompliance included missed opportunities for the fourth Haemophilus influenzae type b vaccine (14.6%), invalid fourth diphtheria-tetanus-pertussis/acellular pertussis immunizations (11.0%), and superfluous polio immunizations (9.8%).


CONCLUSIONS
Approximately 35.6% of children were compliant with prevailing childhood immunization recommendations from 1996 to 1999. Efforts to improve compliance with guidelines are recommended, to optimize childhood infectious disease prevention.
Mell
Loren K
LK
Center for Health Studies, Group Health Cooperative, Seattle, Washington, USA.
Ogren
David S
DS
Davis
Robert L
RL
Mullooly
John P
JP
Black
Steven B
SB
Shinefield
Henry R
HR
Zangwill
Kenneth M
KM
Ward
Joel I
JI
Marcy
S Michael
SM
Chen
Robert T
RT
D015331:Cohort Studies; D016208:Databases, Factual; D017408:Guidelines as Topic; D006279:Health Maintenance Organizations; D006801:Humans; D007114:Immunization / Q000706:statistics & numerical data*; D007115:Immunization Schedule; D007223:Infant; D010349:Patient Compliance / Q000706:statistics & numerical data*; D014481:United States; D014612:Vaccines
D014612:Vaccines