Factors Influencing Completion of Multidose Vaccine Schedules in Adolescents

A Systematic Review

K. E. Gallagher; E. Kadokura; L. O. Eckert; S. Miyake; S. Mounier-Jack; M. Aldea; D. A. Ross; D. Watson-Jones


BMC Public Health. 2016;16(172) 

In This Article


Search Strategy

A comprehensive set of search terms was built around: 1) childhood/adolescence; 2) vaccination/immunisation; 3) adherence/completion. Articles with at least one term from each topic were identified. Search terms were informed by the Cochrane Child Health Group recommended terms for adolescents or school children[23] and included international spelling variations (Additional file 1: Table S1 https://static-content.springer.com/esm/art%3A10.1186%2Fs12889-016-2845-z/MediaObjects/12889_2016_2845_MOESM1_ESM.docx). Multi-dose vaccines administered to adolescents were identified through the Centers for Disease, Control, and Prevention (CDC),[6,24] and the WHO list of prequalified vaccines;[25] however, search terms were not limited to these vaccines.

Medline, Embase, Global Health (Ovid SP), Popline, Web of Science, Africa Portal, Africa-wide information, ADOLEC, Cochrane, Open Grey databases, and PATH, Gavi, and WHO websites were searched in February 2014. No publication date restriction was set. Publications, abstracts and conference proceeding were eligible for inclusion. All texts were collated and reviewed using Endnote X7 (Thompson Reuters); automated and manual de-duplication was performed.

Inclusion Criteria

Inclusion criteria for consideration of studies were outlined in a protocol a-priori as per PRISMA guidelines[26] (Table 2). The title and/or abstract of each article were reviewed in the first instance by a single reviewer (KG). Modelling studies, immunogenicity/efficacy trials were excluded. Two reviewers (KG, SM/EK) screened the abstracts. Any study including a vaccine for which more than one dose was administered to persons 9–19 years old in a routine setting within 1 year was considered for inclusion. The WHO definition of adolescent (10–19 years old) was widened to include 9 year olds to include all participants in HPV vaccine studies (WHO recommended for 9–13 year olds). Inclusion criteria were independently applied to full texts by 2 authors (KG, SM/EK) (Fig. 1).[26]

Figure 1.

Systematic review flow diagram. Caption: the PRISMA flow diagram for the systematic review detailing the database searches, the number of abstracts screened and the full texts retrieved. *Some articles analysed >1 vaccine

Data Extraction

Data were extracted by 2 authors (KG, EK) into separate forms on Microsoft Excel 2010. Article selection and data extraction discrepancies were resolved through discussion. Data on the study population, setting, vaccine, rates of completion and the factors investigated were extracted alongside descriptive, univariate and multivariate results, as applicable.

Assessment of Bias

An assessment of bias was recorded on the data extraction form for each study using criteria outlined in the Cochrane tool for assessment of bias in intervention and epidemiological studies.[27] Selection bias and information bias were assessed alongside the potential for confounding.

Data Synthesis

Heterogeneity in study methods, population, context and classification of exposure variables, led to a descriptive synthesis. Groups which initiated and completed the recommended vaccine schedule within 1 year were compared to non-completers who only initiated.