Barriers to vaccination in Latin America: A systematic literature review.

Current vaccination coverage rates in Latin America and the Caribbean (LAC) are lower than the region-wide rates set by the Pan American Health Organization. To improve vaccination uptake, it is crucial to identify barriers to vaccination. We conducted a systematic literature review to identify the key barriers to vaccination in the LAC region, and to classify and quantify factors affecting vaccination coverage using the barrier categories outlined by the Strategic Advisory Group of Experts (SAGE) working group. We mapped knowledge gaps in the understanding of region-specific and population-specific vaccine hesitancy. Nine databases (Medline via PubMed, Web of Science, LILACS, MedCarib, SciELO, Scopus, PATH, SAGE Online and Google Scholar) were searched for articles published in English, Spanish and Portuguese up to 15 July 2017. A total of 6867 articles were identified of which 75 were included in the review. Majority of the articles were quantitative in nature and nearly half from Brazil. Many other countries in LAC have limited published evidence on barriers to vaccination. The most commonly investigated target population was parents (of children <8 years of age [yoa] and adolescents 9-10 yoa) but there was a balance in the number of publications that reported on influenza, childhood and human papillomavirus vaccination. There was limited direct evidence which reported insights on the new generation of childhood vaccines (pneumococcal or meningococcal vaccines) or studies targeting adolescents and pregnant women. Among the SAGE barrier categories, 'individual/group influences' were the most frequently reported barrier category (68%) followed by 'contextual influences' (47%). Adverse socioeconomic factors, a low level of education, lack of awareness of diseases and their vaccines, religious and cultural beliefs are commonly cited as obstacles to vaccination acceptance. Additional evidence is needed to fully understand the barriers to vaccination for different target populations, countries in the region and specific vaccine types.

Vaccination herd effect experience in Latin America: a systematic literature review.

BACKGROUND: National pediatric vaccination programs have been introduced in Latin America (LatAm) to reduce the burden of diseases due to pathogens such as rotavirus, Haemophilus influenzae type b (Hib) and pneumococcus. Vaccination health benefits may extend to unvaccinated populations by reducing pathogen transmission. Understanding herd effect is important for implementation and assessment of vaccination programs. The objective was to conduct a systematic review of published epidemiological evidence of herd effect with Hib, rotavirus and pneumococcal conjugate vaccines (PCV) in LatAm. METHODS: Searches were conducted in PubMed, Virtual Health Library (VHL), SciELO and SCOPUS databases, for studies reporting data on herd effect from Hib, rotavirus and PCV vaccination in LatAm, without age restriction. Searches were limited to articles published in English, Spanish or Portuguese (1990-2016). After screening and full-text review, articles meeting the selection criteria were included to be critically appraised following criteria for observational and interventional studies. The presence of a herd effect was defined as a significant decrease in incidence of disease, hospitalization, or mortality. RESULTS: 3,465 unique articles were identified, and 23 were included (Hib vaccine n = 5, PCV n = 8, rotavirus vaccine n = 10). Most studies included children and/or adolescents (age range varied between studies). Studies in adults, including older adults (aged > 65 years), were limited. Few studies reported statistically significant reductions in disease incidence in age groups not targeted for vaccination. Hib-confirmed meningitis hospitalization decreased in children but herd effect could not be quantified. Some evidence of herd effect was identified for PCV and rotavirus vaccine in unvaccinated children. Evidence for herd effects due to PCV in adults was limited. CONCLUSION: After introduction of Hib, PCV and rotavirus vaccination in LatAm, reductions in morbidity/mortality have been reported in children not targeted for vaccination. However, due to methodological limitations (e.g. short post-vaccination periods and age range studied), there is currently insufficient evidence to quantify the herd effect in adult populations. More research and higher quality surveillance is needed to characterize herd effect of these vaccines in LatAm.

Maternal immunization: where are we now and how to move forward?

Pregnancy and the postpartum period are associated with elevated risks to both mother and infant from infectious disease. Vaccination of pregnant women, also called maternal immunization, has the potential to protect pregnant women, foetuses and infants from several vaccine-preventable diseases. Maternal immunoglobulin G antibodies are actively transferred through the placenta to provide passive immunity to new-borns during the first months of life, until the time for infant vaccinations or until the period of greatest susceptibility has passed. Currently, inactivated influenza, tetanus, and pertussis vaccines are recommended during pregnancy in many countries, but other vaccines may also be administered to pregnant women when risk factors are present. Several new vaccines with a specific indication for use during pregnancy are under development (e.g. respiratory syncytial virus and group B streptococcus vaccines). Years of experience suggest that maternal immunization against influenza, tetanus or pertussis has an acceptable safety profile, is well tolerated, effective and confers significant benefits to pregnant women and their infants. This review describes the principles of maternal immunization and provides an update of the recent evidence regarding the use and timing of maternal immunization. Finally, the barriers preventing wider vaccination coverage and the current limitations in addressing these are also described ( Supplementary Material ). Key messages Maternal immunization gives pregnant women greater protection against infectious diseases; induces high levels of maternal antibodies that can be transferred to the foetus; and helps protect new-borns during their first months of life, until they are old enough to be vaccinated. Pregnant women and new-borns are more vulnerable to infectious diseases than the overall population; nevertheless, vaccination rates are often low in pregnant women. This review provides an update of the recent evidence regarding the use and timing of maternal immunization and describes the barriers preventing wider vaccination uptake and the current limitations in addressing these.

Vaccine impact: Benefits for human health.

Unlike most drugs, whose benefit is restricted to the individual who takes the drug, prophylactic vaccines have the potential for far-reaching effects that encompass health service utilisation, general health and wellbeing, cognitive development and, ultimately, economic productivity. The impact of immunisation is measured by evaluating effects directly on the vaccinated individual, indirectly on the unvaccinated community (herd protection), the epidemiology of the pathogen (such as changing circulating serotypes or prevention of epidemic cycles), and the additional benefits arising from improved health. Aside from protection of the individual, the broader success of immunisation is dependent on achieving a level of coverage sufficient to interrupt transmission of the pathogen. When evaluating the cost-effectiveness of vaccines, all of these potential benefits need to be accounted for. In many countries where immunisation programmes have been highly successful, the control of disease has meant that the benefits of immunisation have become less obvious. Once a well-known and much-feared disease appears to have disappeared, individuals, including healthcare professionals, no longer view ongoing prevention with the same sense of urgency. Reduced coverage is inevitably associated with resurgence in disease, with outbreaks potentially leading to significant morbidity and loss of life. Ensuring the continued success of immunisation programmes is the responsibility of all: individuals, healthcare professionals, government and industry.

Safety and immunogenicity profiles of an adjuvanted seasonal influenza vaccine in Guatemalan children.

INTRODUCTION: The efficacy of non-adjuvanted seasonal influenza vaccine in young children is considered to be suboptimal. This study compared the safety and immunogenicity profiles of MF59-adjuvanted, trivalent, influenza vaccine (ATIV) and non-adjuvanted, trivalent, influenza vaccine (TIV) in Guatemalan children (N = 360) between 6 and < 60 months of age. METHODOLOGY: Children received two doses of ATIV or TIV administered four weeks apart. Solicited adverse reactions were recorded for seven days after each vaccination. Serious adverse events were recorded throughout the entire study period. Antibody responses were assessed by hemagglutination inhibition (HI) assay at baseline, four weeks after administration of the first vaccine dose, and three weeks after administration of the second dose. RESULTS: Both ATIV and TIV were well tolerated, with similar rates of solicited reactions and adverse events observed in response to both vaccines. MF59-adjuvanted vaccine induced considerably higher antibody titers than did TIV. After two doses, the B strain-specific antibody response to TIV was insufficient to meet the Center for Biologics Evaluation and Research (CBER) licensure criterion for seroprotection, whereas responses to the MF59-adjuvanted vaccine met the seroprotection criterion against all three strains. Cross-reactive antibody responses to MF59-adjuvanted vaccine met the CBER seroprotection criterion against all three strains after two doses; B strain-specific heterologous responses to non-adjuvanted TIV were inadequate. CONCLUSIONS: The MF59-adjuvanted seasonal influenza vaccine was well-tolerated and highly immunogenic in children 6 to < 60 months of age, inducing seroprotective antibody titers against both the vaccine strains and antigenically distinct heterologous strains.

[Consensus on the clinical and microbiologic diagnosis of Bordetella pertussis, and infection prevention. Expert Group on Pertussis Vaccination]. / Consenso para el diagnóstico clínico y microbiológico y la prevención de la infección por Bordetella pertussis. Grupo de expertos en vacunación contra tos ferina.

Pertussis continues to be responsible for a significant disease burden worldwide. Although immunization practices have reduced the occurrence of the disease among children, waning vaccine- and infection-induced immunity still allows the disease to affect adolescents and adults who, in turn, can transmit the disease to non-immunized or partially immunized infants. This document is the result of a meeting in Mexico City of international experts who analyzed recent medical information in order to establish the current status of the epidemiology, diagnosis and surveillance of pertussis and, especially, the value of the dTpa booster dose in adolescents and adults as a pertussis prevention strategy in Mexico.

Consenso para el diagnóstico clínico y microbiológico y la prevención de la infección por Bordetella pertussis / Consensus on the clinical and microbiologic diagnosis of Bordetella pertussis, and infection prevention

La tos ferina sigue siendo responsable de una carga de enfermedad importante en el mundo. Aunque la implementación del uso de la vacuna contra esta enfermedad ha disminuido en gran medida el número de casos en la población pediátrica, se ha observado que la inmunidad inducida por la vacuna y por la infeccion natural disminuye con el tiempo lo que hace nuevamente susceptibles a adolescentes y adultos jóvenes que pueden transmitir la enfermedad a lactantes no inmunizados o con esquema de vacunación incompleto. Este documento, resultado de la reunión de un grupo internacional de expertos en la Ciudad de México, ha analizado la información médica reciente para establecer el estado actual de la epidemiología, diagnóstico, vigilancia y, especialmente, el valor de la dosis de refuerzo con dTpa en adolescentes y adultos como estrategia de prevención de tos ferina en México.

Pertussis continues to be responsible for a significant disease burden worldwide. Although immunization practices have reduced the occurrence of the disease among children, waning vaccine- and infection-induced immunity still allows the disease to affect adolescents and adults who, in turn, can transmit the disease to non-immunized or partially immunized infants. This document is the result of a meeting in Mexico City of international experts who analyzed recent medical information in order to establish the current status of the epidemiology, diagnosis and surveillance of pertussis and, especially, the value of the dTpa booster dose in adolescents and adults as a pertussis prevention strategy in Mexico.