Barriers to Vaccination in Latin America: A Systematic Literature Review

"To improve vaccination uptake, it is crucial to identify barriers to vaccination."

Vaccination coverage rates in Latin America and the Caribbean (LAC) are lower than the region-wide target of 95% set by the Pan American Health Organization (PAHO). This systematic literature review was undertaken with the aim of identifying the key drivers of vaccine hesitancy as a barrier to vaccination uptake in the LAC region and to classify and quantify factors affecting vaccination coverage, according to the barrier categories outlined by the Strategic Advisory Group of Experts (SAGE) working group. In addition, the review aims to identify knowledge gaps for understanding country-, population-, and vaccine-specific determinants of vaccine hesitancy in the LAC region.

The article introduces the concept of vaccine hesitancy; in brief:

• The SAGE working group defines vaccine hesitancy as the "delay in acceptance or refusal of vaccination despite availability of vaccination services".
• Vaccine hesitancy is said to be influenced by 3 main factors: (i) confidence, which is the lack of trust in the vaccine or provider; (ii) complacency, which is the perception there is no value or a need for a vaccine; and (iii) convenience, which refers to the perceived lack of access or services towards vaccination.
• The SAGE working group's "Model of Determinants of Vaccine Hesitancy" is organised around 3 key barrier categories: (i) contextual influences, which are affected by historic, socio-cultural, health system, economic, or political determinants; (ii) individual/group influences, which are impacted by personal perceptions of the vaccine or influences of the social environment; and (iii) vaccine- and vaccination-specific issues, which are directly related to the characteristics of the vaccine or the vaccination process.
• The determinants of vaccine acceptance are complex and context-specific, varying across time, place, and vaccines.

The systematic literature involved searching 9 databases (Medline via PubMed, Web of Science, LILACS, MedCarib, SciELO, Scopus, PATH, SAGE Online, and Google Scholar) for articles on barriers to vaccination in the region that were published in English, Spanish, and Portuguese up to July 15 2017. A total of 6,867 articles were identified, of which 75 were included in the review. A descriptive knowledge gap analysis was then conducted.

The majority of the articles were quantitative in nature, and nearly half were from Brazil. The most commonly investigated population was parents (of children under 8 years of age and adolescents aged 9-10), but there was a balance in the number of publications that reported on influenza, childhood, and human papillomavirus (HPV) vaccination. There was limited direct evidence which reported insights on the new generation of childhood vaccines (pneumococcal or meningococcal vaccines) or studies focused on adolescents and pregnant women.

Among the SAGE barrier categories, obstacles to vaccination acceptance examined in the literature included:

• The most frequently reported was "individual/group influences" (68%), with 33% in this category grouped under 'risks/benefits (perceived)', including safety concerns, 29% grouped under 'knowledge and awareness', and 26% related to 'beliefs, attitudes, and motivation about health and prevention'.
• Next were barriers related to "contextual influences" (47%), with 41% of these related to 'socio-economic, religion, culture and gender', followed by 'geographic barriers' (7%) and 'communication and media environment' (4%).
• In the ‘vaccine and vaccination-specific issues’ barrier category (reported in 23% of the studies), 9% of publications discussed the 'role of healthcare professionals', and 7% discussed the 'reliability of vaccine supply' and 'costs'.

In reflecting on the findings, the researchers note that the World Health Organization (WHO) Global Vaccine Action Plan includes measurements of confidence as an indicator of success towards achieving its immunisation goals. Therefore, it is not surprising that individual/group influences - and, especially, beliefs and attitudes towards vaccination - are the most commonly reported barrier to vaccination uptake in the LAC region, irrespective of the vaccine type. Despite this general observation, the review found that barriers to vaccine and vaccination-specific issues have different determinants in different regions; thus, the researchers call for action at a sub-regional level with tailored solutions to meet each sub-region's needs.

In that vein, additional evidence is needed to fully understand the barriers to vaccination for different populations, countries in the region, and specific vaccine types. For example, more studies are needed to understand vaccination practices amongst adolescents in the LAC region. "This is essential as during adolescence, new information is acquired from many sources and educational programs on vaccines and related diseases would increase awareness and knowledge of future parents..." In addition, vaccine accessibility is seen to be an issue in all levels of the vaccination process; thus, barriers to accessibility need to be characterised and studied further, they argue.

Some general recommendations include:

• Higher levels of education and trust in healthcare workers favour vaccine acceptance; thus, these factors should be considered in the implementation of strategies to increase vaccination uptake.
• Educational programmes for families and social mobilisation emphasising the benefits of vaccination and the consequences of vaccine-preventable diseases could help improve vaccination coverage.
• Other factors to address barriers to uptake include providing adequate financial support and streamlining regulatory procedures for the introduction of new vaccines in the region.

The researchers conclude that the evidence base from this review could be beneficial for decision- and policy-makers who discuss vaccination implementation strategies, especially those related to new population groups or new vaccines in the region.