Since late 1990, CCT programs have been implemented and evaluated in Latin America and the Caribbean. The main feature of such programs is the provision of monetary support and investment in human capital, and in return the beneficiaries must meet certain actions that promote good health and nutrition, and increase their educational levels.
Much of the empirical support on the impact of CCT programs on health and nutrition comes from studies evaluating Oportunidades. However, several systematic reviews on the impact of CCT programs, have found an increase in the use of health services for diverse populations (prenatal, children <5 years, children 6–17 years and adults ≥ 18 years), and a decrease on diarrhea in children, and the percentage of mothers who reported illness in children [45, 46].
In another vein, the impact of CCT programs on the prevalence of vaccination has been studied primarily in children. For example, the Familias en Acción program (Colombia) increased the probability that children have complied with the DPT vaccination schedule , while the Asignación Familiar program (Honduras) showed an increase in immunization coverage of DPT-Pentavalent in children less than three years . Meanwhile, the Red de Protección Social (Nicaragüa) led to large increases in complete schedule vaccination coverage . Finally, the Oportunidades program showed a positive effect on the application of BCG in children aged 12–23 months and an increase in vaccination coverage against measles in children 12–23 months .
Our study, on the other hand, is part of the global evaluation of the Oportunidades program and is based on a large sample of poor and rural elderly persons. To the best of our knowledge, it constitutes the first empirical effort aimed at investigating the association between CCT program participation and vaccination coverage for OP. According to the results, the participation of households with OP enrolled in Oportunidades, one of the largest CCT programs in the world, entailed a significant increase in the immunization coverage for the elderly with regard to tetanus, pneumococcal and influenza vaccines, and the complete vaccination schedule. It should be noted, however, that the immunization rates for this population continue to lag, particularly when compared to the standards established under the 2007–2012 Mexican National Health Plan , where a goal of at least 85% coverage was set for the basic OP vaccination schedule.
With respect to the hypothesis of our study, we believe that the program's effect is not only due to the mandatory six-monthly check-ups for the OP, but could be related to the fact that beneficiaries of the program have experienced a learning process regarding the use of services health, and the benefits that entails for health .
Additionally, the results of this study support the mounting evidence on the short-term benefits of CCT programs for various health indicators in low- and middle-income countries [21, 53–55]. However, an important aspect that is omitted from the literature and should be addressed by future research is an analysis investigating the factors mediating the relationship between Oportunidades program participation and vaccination coverage specifically and access to health services for the OP population in general. For instance, it is important to determine what roles other government institutions in Mexico (Ministry of Health and the National Institute of Older Adults) play in vaccination coverage. Further, beyond overall program participation, it is important for future research to identify specifically how the obligatory medical checkups required by Oportunidades affect vaccination.
Our results suggest that interventions to increase household income could increase vaccination coverage among OP. This could be an argument to promote interventions consisting in conditional cash transfers or non-contributory pension schemes for OP, which is expected to increase older people’s economic and physical autonomy. Autonomy is an essential component of older people’s well-being, to the extent that the World Health Organization in its Active ageing policy proposes that it should be considered a key element of programs aimed at this population group.
Several limitations can be noted in our study. First, despite the rigorous matching methods applied to minimize the possibility of an OP selection bias regarding program participation, the causal inferences in the conclusions are not as powerful as they would have been had the study been executed under a purely experimental design. Notwithstanding, it is worth mentioning that another Oportunidades study with a methodology comparable to ours confirmed that analogous results are obtained under a quasi-experimental and a wholly experimental approach .
Second, the study should be considered as a conservative estimate of program effects. Seeking to minimize selection bias, the original sample size and, consequently, the power of the study were cut down. Nonetheless, the final matched sample size (2314 OP in each group, Oportunidades and Non-Oportunidades) allowed for detecting differences of up to 3.5 percentage points with a power of 90%.
Third, the self-reported vaccination status by the OP or his/her caregiver was estimated as the measure of the outcome variable. Again, while some studies have demonstrated the validity of self-report vaccination among various OP populations [57–59], the question arises as to whether these study populations were rural and extremely poor as well. A study should therefore be conducted to verify if the validity of self-reporting remains applicable in our case.
Fourth, the data associated with the Oportunidades evaluation study in rural areas of Mexico was collected in 2007, just two years before the 2009 H1N1 influenza pandemic, which changed the public awareness of vaccination and the health literacy. In fact, for example, Mexico now has the highest rate of vaccination against influenza among OECD countries . The implications of this for our evaluation results are not clear; but the program impact may be even greater since the program's beneficiaries, mostly poor, have been a target population to which efforts have been directed to increase vaccination coverage against influenza.
Lastly, although the safety, effectiveness and cost-effectiveness of OP vaccination schedules have been documented , the direct and significant impact of vaccination on specific OP physical health indicators is still pending analysis.