Individual level determinants for not receiving immunization, receiving immunization with delay, and being severely underimmunized among rural western Kenyan children.
BACKGROUND
Estimating vaccination coverage and delays are important because these measures can identify at risk sub-populations who can be targeted with interventions and public health policies. This paper sought to determine estimates and risk factors for children in rural western Kenya who did not receive immunization, received immunization with delay, or were severely underimmunized.


METHODS
Caregivers of children aged 12-23 months old were surveyed for immunization history using written records from the immunization booklet. Risk factors for not receiving immunization, delayed immunization, and severe underimmunization were calculated using log-binomial regression. Children were categorized as delayed if a given immunization was received greater than four weeks from the age-appropriate scheduled date. Severely underimmunized children were those who were fully unvaccinated for more than 90 days and had three or more vaccines delayed or not given.


RESULTS
Immunization coverage for pentavalent1, pentavalent3, measles, and fully immunized child (FIC; BCG, three doses of polio, three doses of pentavalent, and measles vaccines) were 99%, 94%, 83%, and 80%, respectively. Approximately, 10%, 24%, and 29%, of children were delayed for pentavalent1, pentavalent3, and measles, respectively. Each model produced a unique combination of risk factors with only advanced maternal age as a risk factor common to all models. Children with delayed receipt of pentavalent1 were at risk for not receiving pentavalent3 (RR: 5.20; 95%CI 3.48, 7.77), measles vaccine (RR: 1.48; 95%CI 1.12, 1.95), and not achieving FIC (RR: 1.88; 95%CI 1.51, 2.34) compared with children who received pentavalent1 on time.


CONCLUSIONS
Immunization coverage among 12-23 month old children was high, yet a substantial proportion of children were vaccinated with delay. Although vaccine coverage and timeliness are often conceptualized as separate measures, the finding that delayed pentavalent1 receipt was a strong risk factor for not receiving future immunizations indicates the two measures are intertwined.
Johns Hopkins Bloomberg School of Public Health, Department of International Health, Baltimore, MD, United States. Electronic address: dgibso28@jhu.edu.
Dustin G
DG
Gibson
Kenya Medical Research Institute/Centers for Disease Control and Prevention Public Health and Research Collaboration, Kisumu, Kenya.
Benard
B
Ochieng
Johns Hopkins Bloomberg School of Public Health, Department of International Health, Baltimore, MD, United States.
Eunice W
EW
Kagucia
Kenya Medical Research Institute/Centers for Disease Control and Prevention Public Health and Research Collaboration, Kisumu, Kenya.
David
D
Obor
Kenya Medical Research Institute/Centers for Disease Control and Prevention Public Health and Research Collaboration, Kisumu, Kenya.
Frank
F
Odhiambo
Johns Hopkins Bloomberg School of Public Health, Department of International Health, Baltimore, MD, United States.
Katherine L
KL
O'Brien
Johns Hopkins Bloomberg School of Public Health, Department of International Health, Baltimore, MD, United States; Division of Viral Diseases, Centers for Disease Control and Prevention, Atlanta, GA, United States.
Daniel R
DR
Feikin
D000293:Adolescent; D000328:Adult; D003430:Cross-Sectional Studies; D005260:Female; D006801:Humans; D007114:Immunization; D007223:Infant; D007630:Kenya; D008297:Male; D055118:Medication Adherence; D012424:Rural Population; D055815:Young Adult
FIC; Fully immunized child; Immunization; Kenya; Underimmunization; Vaccination; Vaccination coverage; Vaccination timeliness