Vacinação infantil em países de baixa e média renda: evidência de relutância em vacinar

Abstract

Immunization is one of the public health interventions with the greatest impact on child morbidity and mortality. Ensuring universal access to essential vaccines by 2030 is a target of the Sustainable Development Goals (SDGs). However, the vaccine hesitancy, defined as a state of conflict about or opposition to receiving vaccines, can jeopardize the advances already achieved by immunization worldwide. The World Health Organization (WHO) recognizes vaccine hesitancy as one of the 10 threats to global health. The general aim of this thesis was to evaluate the presence of vaccine hesitancy in low- and middle-income countries (LMICs). Three studies were conducted with the following objectives: (I) to assess whether the social gradient, with higher immunization coverage observed among the richest compared to the poorest, is reversing in the LMICs; (II) to estimate the cumulative impact of mothers receiving primary health care interventions in immunization coverage of their children and; (III) to compare the time trends in immunization coverage with other maternal and household indicators. We used data from population surveys conducted in LMICs, Demographic and Health Surveys and Multiple Indicator Cluster Surveys. Three outcomes were evaluated: (I) full vaccination coverage (FIC) with basic vaccines, defined as children aged 12 to 23 months who received one dose of Bacille Calmette-Guérin (BCG) vaccine, three doses of diphtheria-pertussis-tetanus (DPT) vaccine, three doses of polio vaccine and one dose of measles vaccine; and (II) DPT vaccine coverage and (III) measles vaccine coverage, i.e., children aged 12 to 23 months who received three doses of DPT vaccine; and one dose of measles vaccine. In the first paper, we studied 86 LMICs and we observed a pro-poor FIC pattern in 20% of the upper-middle income countries, that is, higher immunization coverage among the poorest than in the wealthiest children. In the second manuscript, the effect of mothers receiving prenatal and postnatal care and having a delivery with a skilled birth professional on their children's FIC was investigated in 86 LMICs. For each intervention received, FIC increased from 9% to 16%, thus, in general, children of women who received the three interventions have higher immunization coverage compared to those who received two or fewer interventions. When dividing this result by income group, we observed in high middle-income countries that multiple health interventions had a lower effect on the FIC when compared to the other countries. In the last manuscript, we compared time trend in immunization indicators (DPT and measles) with time trends in maternal (prenatal consultations and delivery at a health institution) and household (improved basic sanitation and better sources of water for consumption) health indicators. We included 63 LMICs, and we found an increase in coverage for all indicators, with institutional delivery with the highest increase and immunization indicators with the smallest increase. In upper-middle-income countries, measles vaccine coverage decreased 0.5 percentage points per year, while the other indicators of women's and household health had an increase of 0.2 to 0.8 percentage points per year. It was not possible to measure vaccine hesitancy directly due to limited data from the databases we used. However, based on the inverse equity hypothesis, which states that health interventions reach the richest groups first, in detriment of the poorest, we believe our findings suggest some level of vaccine hesitancy mainly in middle-income countries.