The Bolivarian Republic of Venezuela's Expanded Program on Immunization (EPI) strives to protect its citizens against vaccine-preventable diseases (VPDs); however, suboptimal performance has left multiple birth cohorts susceptible to VPDs. Over the past 3 decades, Venezuela has achieved <85% reported coverage with third dose of diphtheria-tetanus-pertussis [DTP3] vaccine, the common indicator for immunization program performance [1]. Groups at risk for suboptimal immunization coverage include indigenous populations, those in border, urban and hard-to-reach zones, displaced populations and those in areas where population growth exceeds the capacity of health services.

Vaccination Week in the Americas (VWA) is an annual initiative carried out by countries and territories in the Region of the Americas and supported by the Pan American Health Organization/World Health Organization (PAHO/WHO) [2,3]. VWA began in 2003 based on a proposal by ministers of health of six countries^a in response to a large measles outbreak in Venezuela and Colombia in 2002 [4]; the proposal called for a coordinated annual international vaccination effort. The initiative’s objectives include highlighting the work of national immunization programs and increasing access to vaccination services, particularly for hard-to-reach, high-risk groups. Specific campaigns undertaken as part of VWA are flexible and chosen by countries based on their public health priorities [5]. VWA’s success has inspired establishment of similar initiatives in other regions, leading to the 2012 launch of World Immunization Week, endorsed by the World Health Assembly [6].

In Venezuela, VWA is a comprehensive initiative encompassing multiple activities including advocacy with political and technical authorities, social communication and mobilization and increased availability of vaccination services. These activities are intended to help position EPI on the political agenda, increase visibility of the program, and improve coverage [7]. The VWA 2011 campaign in Venezuela included targeting children aged less than 6 years of age who were eligible for one or more vaccine doses in the national schedule (Table 1), with emphasis on those who lived in one of 25 high risk border municipalities, selected based on reported low coverage the year prior. The main strategy was increased social mobilization for institution-based vaccinations. Across the region, VWA 2011 was officially scheduled from April 23^rd to April 30^th, but in Venezuela it extended through the month of May.Table 1

Routine vaccination schedule in Venezuela, 2011

Bolivar is one of 29 municipalities in the western Andean state of Táchira and was one of the prioritized areas during VWA 2011. Bolivar is located on Venezuela’s border with the Republic of Colombia and experiences constant population movement due to commercial activities between the two countries; in 2011, the population of Bolivar was 74,568 individuals [8]. Because the municipality contains urban, periurban, and rural areas, as well as displaced populations, the Venezuelan Ministry of Health (MOH) selected Bolivar as the site for an evaluation of VWA 2011, including a post-VWA immunization coverage survey [9]. This coverage survey was supported by PAHO and the United States Centers for Disease Control and Prevention (CDC) and represents one of the few methodologically rigorous evaluations performed over the 12 years of VWA.

Although one of VWA’s objectives in Bolivar in 2011 was to improve immunization coverage, only an estimated 24% of eligible children received at least one indicated vaccine dose and only 13% received all doses due. Overall, there was low awareness of VWA 2011; less than one-third of caregivers heard about recent vaccination activities, which may have limited the initiative’s reach. Nevertheless, vaccine coverage for most vaccines at the time of the survey was above 85%.

The proportion of children who benefitted from VWA 2011 was likely lower than our estimates indicate. Because VWA 2011 in Bolivar focused on increasing vaccination services in institutional settings that already provided them, we were unable to distinguish between vaccine doses provided because of VWA and those administered irrespective of VWA. In addition, the largest proportion of eligible children vaccinated were those who received BCG or birth dose of hepatitis B vaccine. However, these doses are typically administered following hospital births and 95% of births in Bolivar are estimated to occur in hospitals [11].

Although coverage with most vaccines was relatively high among all cohorts, MMR1 coverage among 12–23 month-olds was lower at 72% (95% CI 63-80%) than among older cohorts (88-93%). Analysis of timeliness demonstrated that older cohorts also had lower levels of coverage during the second year of life; however, continuing to offer immunization services to older children resulted in higher coverage during succeeding months and years, similar to findings reported elsewhere [12]. While the scope of this study did not address specific reasons for the receipt of late doses, particularly for Penta2 and Penta3, speculative reasons may include population movement across the border to Colombia for extended periods of time for employment, delaying the completion of schedules until families return to Venezuela, work obligations which limit the ability of parents to bring their children to the health centers during regular hours and the reduced use of house-to-house vaccination strategies. Such concerns were part of the reason that border municipalities were prioritized during VWA 2011 in Venezuela, as the initiative represents one strategy to identify those children with incomplete schedules and improve coverage.

Social mobilization to raise population awareness of public health interventions is essential [13-16], especially for institution-based efforts that require population turnout at health centers, as opposed to strategies such as house-to-house vaccination. Implementation of the VWA 2011 communication campaign was decentralized to the local level and had limited oversight from the national EPI. In the future, efforts to ensure messages about VWA reach a wide audience should use communication channels identified by caregivers in this evaluation, such as radio and health centers. While access to vaccination services was beyond the scope of this survey, it merits further examination, especially in a border municipality such as Bolivar which has high population mobility.

High prevalence of vaccination cards in households, high participation rate among caregivers aware of vaccination activities, and widespread use of public facilities for vaccination services indicate public support of EPI in Bolivar. Among children vaccinated, 45% did not receive all indicated vaccines. This may be due to multiple reasons, including those related to health care workers who may have been uncomfortable administering multiple vaccines, had misconceptions about contraindications, or were hesitant to open new vaccine vials for fear of wastage. There may have also been unknown vaccine and supply shortages and it is possible that parents may have been uncomfortable with their child receiving multiple vaccinations on the same day, among many other potential reasons [16,17]. To prevent such missed opportunities in the future, additional health worker training and assessments of parental satisfaction regarding their experience with the EPI should be considered.

Coverage for Penta3 in Bolivar was higher than the national coverage of 78% reported by Venezuela through the WHO/UNICEF Joint Reporting Form for 2011 [18]. Lower coverage for yellow fever vaccine, especially among children aged 12–23 months (63%) is likely due to global vaccine shortages, causing stock-outs. Rotavirus vaccine was introduced in Venezuela in 2006; because of this and the upper age limits for administering vaccine, older children would have aged-out of eligibility to receive the vaccine post-introduction, resulting in lower coverage in these cohorts. The schedule for rotavirus vaccination was modified in 2009, an operational change that could have also affected coverage. Other recent EPI schedule changes include the introduction of MMR2 and second OPV and DTP boosters during 2009–2010. These changes may explain the lower coverage for these doses as health workers adapted to new guidelines.

While our results exposed positive and negative aspects of implementation of VWA 2011 and the overall EPI in Bolivar, Venezuelan health authorities have used lessons learned for planning of subsequent vaccination activities. For example, efforts to improve VWA social communication and mobilization intensified in Bolivar in 2012, 2013 and 2014, including new strategies such as using loudspeakers. To optimize performance of routine EPI, local health authorities have subdivided parishes of the municipality and reassigned health workers to better reach the population. Health authorities have also coordinated with community councils to conduct house-to-house vaccination in specific difficult-to-reach and low coverage areas. An additional vaccination post was also opened in a hospital in Bolivar with extended evening hours to increase opportunities for working parents to have their children vaccinated.

The survey in Bolivar had several limitations. The survey was completed by multiple teams during an intensive two-day effort over a weekend when most parents are home. This decision was made to complete the survey quickly in order to maximize the efficiency of the data collection process. The use of multiple teams may have increased the risk of bias, but efforts were in place to train and closely supervise the interviewers. The survey design was based on a quota sample of households with at least one eligible child and not probability sampling. As a result, we could not calculate the selection probability of households or account for non-response. To accurately determine VWA 2011 eligibility, we restricted analysis to children with available vaccination records. This may have led to overestimation of coverage; however, because card availability was high overall within each age group, this bias was likely minimal.

Our evaluation provided important information regarding the implementation and outcome of VWA 2011 in one border municipality, and provided insight into the performance of EPI in this challenging and dynamic area. Because of the targeted nature of the survey, findings cannot be generalized to VWA 2011 results in other areas of the country, nor do they assess all components of Venezuela’s multi-faceted VWA 2011 campaign. As Vaccination Weeks evolve within the framework of World Immunization Week, similar surveys, adapted to local realities, can help objectively assess execution and outcomes of similar initiatives aimed at improving coverage and updating childhood vaccination schedules, while providing lessons to adjust strategies and optimize results. Such surveys also serve as windows into routine EPI implementation at the local level, and are thus important management tools. Constructive activities following survey results, such as Venezuela’s response since 2011, will help ensure that populations are protected against VPDs and that disease eradication, elimination and control goals are achieved and maintained.

^aBolivia, Chile, Colombia, Ecuador, Peru, and Venezuela

^bIncluded nurses, “simplified medicine” assistants, and social workers;

^cPentavalent vaccine contains diphtheria toxoid, tetanus toxoids, pertussis vaccine, Haemophilus influenzae type b (Hib) vaccine, and hepatitis B vaccine.