Vaccination coverage and immunization timeliness among children aged 12-23 months in Senegal: a Kaplan-Meier and Cox regression analysis approach

Abstract

IntroductionExpanded programme on immunizations in resource-limited settings currently measure vaccination coverage defined as the proportion of children aged 12-23 months that have completed their vaccination. However, this indicator does not address the important question of when the scheduled vaccines were administered. We assessed the determinants of timely immunization to help the national EPI program manage vaccine-preventable diseases and impact positively on child survival in Senegal.MethodsVaccination data were obtained from the Demographic and Health Survey (DHS) carried out across the 14 regions in the country. Children were aged between 12-23 months. The assessment of vaccination coverage was done with the health card and/or by the mother’s recall of the vaccination act. For each vaccine, an assessment of delay in age-appropriate vaccination was done following WHO recommendations. Additionally, Kaplan-Meier survival function was used to estimate the proportion vaccinated by age and cox-proportional hazards models were used to examine risk factors for delays.ResultsA total of 2444 living children between 12–23 months of age were included in the analysis. The country vaccination was below the WHO recommended coverage level and, there was a gap in timeliness of children immunization. While BCG vaccine uptake was over 95%, coverage decreased with increasing number of Pentavalent vaccine doses (Penta 1: 95.6%, Penta 2: 93.5%: Penta 3: 89.2%). Median delay for BCG was 1.7 weeks. For polio at birth, the median delay was 5 days; all other vaccine doses had median delays of 2-4 weeks. For Penta 1 and Penta 3, 23.5% and 15.7% were given late respectively. A quarter of measles vaccines were not administered or were scheduled after the recommended age. Vaccinations that were not administered within the recommended age ranges were associated with mothers’ poor education level, multiple siblings, low socio-economic status and living in rural areas.ConclusionA significant delay in receipt of infant vaccines is found in Senegal while vaccine coverage is suboptimal. The national expanded program on immunization should consider measuring age at immunization or using seroepidemiological data to better monitor its impact.

Coverage and Determinants of Full Immunization: Vaccination Coverage among Senegalese Children

“…Our study observed a seven percentage point decline in coverage of immunization from BCG at birth (95.33%) to measles (88.69%) to be administrated after nine months of birth. Similar findings were also found in earlier studies, however, this coverage gap has been reduced over time [8,9]. This finding indicates the prevalence of missed opportunities and the challenge of introducing measles vaccine routinely after the ninth month of birth.…”

“…EPI program in Senegal recommends that a child should receive BCG (Bacillus of Calmette–Guerin) vaccine against tuberculosis soon after birth, oral polio vaccine (OPV), and the monovalent pneumococcal conjugate vaccine (PCV) at birth and at 6th, 10th and 14th week, and at 9th month. Since 2005, DPT vaccine had been replaced by pentavalent vaccine which contains a combination of five vaccines in one dose i.e., diphtheria, tetanus toxoid, pertussis, hepatitis B, and Hemophilus influenza type b vaccine (Hib) and recommended to be administered at the same time as the OPV or PCV at 6th, 10th, and at 14th week from birth (Table 1) [9]. Since measles is highly endemic and frequently affects infants in Senegal, routine measles vaccination is recommended at the 9th month of age with a second dose at 15th month.…”

“…Since measles is highly endemic and frequently affects infants in Senegal, routine measles vaccination is recommended at the 9th month of age with a second dose at 15th month. Additionally, a dose of yellow fever is also given at the age of nine months [9,10]. Regardless of successes, vaccine-preventable diseases are the leading cause of childhood mortality in Senegal while the under-five child mortality rate is still high as 45 per 1000 live births [11,12].…”

An Overview of Coverage of BCG Vaccination and Its Determinants Based on Data from the Coverage Survey in Zhejiang Province

“…The cumulative probability of being vaccinated for BCG was estimated at age t through the inverse Kaplan–Meier survival function [ 21 ], the number of days of delay based on the maximum age at which the vaccination was recommended. Hence, the first day of delay of BCG was defined as the first day after the first 28 days of life.…”

Cobertura y factores asociados a la vacunación contra el sarampión en niños de 12 a 59 meses en Perú: estimación basada en la Encuesta Demográfica y de Salud Familiar 2017

“…La mayoría de los estudios que han estimado coberturas de vacunación contra sarampión usando las encuestas demográficas y de salud (DHS) fueron realizados en países africanos. En Senegal fueron realizados dos estudios, los cuales reportan coberturas de 82,1% en 2199 niños de 12 a 23 meses (DHS 2010-2011) (15) y 79,2% en 2444 niños de 12 a 23 meses (DHS 2013-2014) (20) ; en el Congo se reportó una cobertura de 70,0% en 6947 niños de 6 a 59 meses (DHS 2013-2014) (16) ; en Etiopía la cobertura fue de 55,7% en 1927 niños de 12 a 23 meses (DHS 2011) (17) ; por último, en Pakistán se reportó 62,5% de cobertura en 9177 niños de 0 a 60 meses (DHS 2006-2007) (14) . Todas las estimaciones presentadas consideraron tanto el recuerdo de la madre, como el obtenido de las tarjetas de vacunación, en nuestro estudio considerando dicha forma de estimación la cobertura nacional tuvo 17,6 puntos porcentuales más para la primera dosis, mientras que para el refuerzo la variación fue mínima, con menos de un punto porcentual de diferencia.…”