Classification of risk for transmission of vaccine-preventable diseases in Brazilian municipalities: comparative analysis before and after the national movement for vaccination and multivaccination proposed by the Ministry of Health as of 2023
The Brazilian National Immunization Program (PNI) was established in 1973 to address the urgent need for stimulating, expanding, and coordinating immunization efforts in Brazil. The PNI is the primary public health strategy for reducing the transmission, complications, and deaths caused by vaccine-preventable diseases . Significant progress has been made in controlling and eliminating certain diseases (such as smallpox, measles, and polio), with the number of different immunobiologicals increasing from four to 48. Additionally, the PNI has expanded coverage across various stages of the Brazilian vaccination calendar over the past five decades . However, failures in preventive actions have contributed to the re-emergence of infectious disease outbreaks, including those caused by vaccine-preventable diseases . One example is the measles outbreak in Brazil, which resulted in the country losing its certification for disease elimination granted by the Pan American Health Organization a few years earlier . Since 2016, there has been a significant decline in vaccination coverage in Brazil, which began in 2012 and has been exacerbated during the COVID-19 pandemic . The progressive decline in vaccination coverage (VC) may have multiple causes, such as: the recent rise of anti-vaccine movements, the rapid spread of misinformation campaigns on social media, the lack of awareness about the risks of diseases, and the increase in vaccine hesitancy among the population [ , , ]. The extent of low coverage in certain scenarios can be determined using indicators that classify the risk of vaccine-preventable disease transmission . For example, in the state of Minas Gerais, there was a significant increase in the percentage of municipalities at high and very high risk for disease transmission in 2021 due to worsening immunization indicators. These indicators include an increase in the abandonment rate of multi-dose vaccines, a decrease in the homogeneity of VC (especially in medium and large municipalities), and a drastic decrease in VC for 10 immunobiologicals in children under two . To address the challenges of low VC, it is crucial to conduct a situational analysis in local administrations. This involves identifying the areas most susceptible to vaccine-preventable disease transmission and developing proposals involving various sectors of the healthcare system, social sectors, and education. Additionally, strategies must be implemented to maintain high VC throughout the country . In this context, the Ministry of Health launched the National Vaccination Movement in 2023. This movement aimed to mobilize the entire population to get vaccinated, aiming to increase and sustain vaccination coverage in the country. The federal government considered this movement a priority in rebuilding the Unified Health System, restoring vaccine confidence, and promoting a vaccination culture in Brazil . Furthermore, to significantly increase vaccination coverage, it was necessary to consider each region’s unique characteristics and plan actions based on social and cultural factors. This decentralized and localized approach aimed to identify, quantify, and reach unvaccinated target populations. States and municipalities utilized microplanning (MP) to understand the local context and ensure the quality of vaccination activities to achieve high VC . Given the decreasing VC in recent years in Brazil and the strategies implemented by the Ministry of Health since 2023 to regain high VC, the objective of this study was to analyze the classification of the risk of vaccine-preventable disease transmission in Brazilian municipalities before and after the National Vaccination and Multivaccination Movement proposed by the Ministry of Health. 

This epidemiological, ecological study uses secondary data on vaccination coverage, dropout rates, and homogeneity of vaccination (HCV) coverage of ten immunobiologicals recommended for children under 2 years of age. The study aims to conduct a comparative analysis between 2022 and 2023 in Brazil. All 5,570 Brazilian municipalities were analyzed and classified by population size, according to the study presented by Braz et al. (2016) , as follows: small size (population less than or equal to 20,000 inhabitants), medium size (population between 20,001 and 100,000 inhabitants), and large size (population greater than or equal to 100,001 inhabitants). The immunobiologicals were analyzed according to the business rules proposed by the Ministry of Health , which include the following vaccines: a second dose of human rotavirus vaccine, a second dose and first booster of meningococcal C conjugate vaccine (Meningo C), meningococcal ACWY conjugate vaccine (MenACWY), a second dose and first booster of pneumococcal 10-valent vaccine (Pneumo 10), third dose of pentavalent vaccine (diphtheria + tetanus + pertussis + hepatitis B + Haemophilus influenzae type B), third dose and first booster of polio vaccine (IPV + OPV), the first and second dose of triple viral vaccine (measles + mumps + rubella), the first dose of yellow fever vaccine, first dose of hepatitis A vaccine, and the first dose of varicella vaccine. The MenACWY vaccine was included in this study because it was temporarily available to children during the evaluated period . The BCG and Hepatitis B vaccines, which are part of the National Childhood Vaccination Calendar, were not evaluated due to their administration primarily in maternity hospitals, which could introduce analysis bias. With regard to the yellow fever vaccine, it has been included in Brazil’s National Vaccination Calendar in all states and municipalities in the country since 2020, gradually including 1,101 municipalities in the northeastern states that were not part of the area with vaccine recommendation (ACRV) ( https://www.gov.br/saude/pt-br/assuntos/saude-de-a-a-z/f/febre-amarela/vacina ). Therefore, as the study considers the years 2022 and 2023, the yellow fever vaccine also needs to be considered in the analysis. The VC data for the year 2022 were extracted from Tabnet/DATASUS through the website http://tabnet.datasus.gov.br/cgi/dhdat.exe?bd_pni/cpnibr.def , and the data for the year 2023 were obtained from the Vaccination Coverage Panel for the vaccines on the National Calendar through the website https://infoms.saude.gov.br/extensions/SEIDIGI_DEMAS_VACINACAO_CALENDARIO_NACIONAL_COBERTURA_RESIDENCIA/SEIDIGI_DEMAS_VACINACAO_CALENDARIO_NACIONAL_COBERTURA_RESIDENCIA.html . Both extractions were done on February 26, 2024, based on household data. The number of doses administered for the multi-dose vaccines was obtained from TabNet/DATASUS (for 2022) and from the National Health Data Network (for 2023). The indicators used for this study are shown in Table . The vaccines were categorized according to the targets specified as adequate by the PNI, which were greater than or equal to 90% for the oral human rotavirus vaccine and greater than or equal to 95% for the others. In terms of homogeneity among vaccines, the criterion proposed by Braz et al. (2016)  was adopted and adapted as follows: adequate homogeneity (≥ 70% to < 100% of vaccines with adequate coverage), low homogeneity (≥ 50% to < 70% of vaccines with adequate coverage), and very low homogeneity (< 50% for the vaccines analyzed with adequate vaccination coverage). The abandonment rate of multi-dose vaccines was assessed for the meningococcal C vaccine, pentavalent vaccine, pneumococcal 10 vaccine, polio vaccine, and oral human rotavirus vaccine. These vaccines were classified as follows: low abandonment rate (< 5%), medium abandonment rate (≥ 5% to ≤ 10%), and high abandonment rate (≥ 10%)11. Finally, Brazilian municipalities were classified according to the risk of transmission of vaccine-preventable diseases in 2022 and 2023, using the five categories described in Table . Due to the low number of municipalities classified as very high risk of transmission of vaccine-preventable diseases, this category was grouped with the high risk of transmission of vaccine-preventable diseases. The data were analyzed using the statistical package Statistical Software for Professional (Stata), version 16.0. Categorical variables were presented as absolute and relative frequencies. For continuous variables, after confirming the asymmetry of the distribution of vaccination coverage in Brazilian municipalities, the paired Wilcoxon test was used to compare the change in median vaccination coverage between the two years analyzed. A significance level of 5% was adopted for the entire analytical procedure. This study was conducted using public domain data, which does not allow individual identification and thus does not require the approval of a Research Ethics Committee. 

The comparative analysis of VC between 2022 and 2023, conducted for ten immunobiologicals, revealed a statistically significant increase in the median VC for all vaccines except for the varicella vaccine (Table ). In 2022, the immunobiologicals analyzed showed that the rotavirus vaccine had the highest proportion (47.45%) of municipalities that reached the recommended vaccination coverage target, followed by the pneumococcal vaccine (46.93%). This pattern continued in 2023, with 63.74% of municipalities achieving the target for the rotavirus vaccine and 54.28% for the pneumococcal vaccine (Fig. ). Regarding the homogeneity of vaccination coverage (HCV), in the years 2022 and 2023, 27.99% of Brazilian municipalities were classified as adequate (≥ 70%), and 410 (7.36%) achieved 100% HCV for all vaccines in 2022. In 2023, 34.90% of municipalities were classified as adequate (≥ 70%), and among them, 582 (10.46%) had 100% HCV for all vaccines. In 2022, the state of Paraná had the highest proportion of municipalities classified as 100% homogeneous for the 10 immunobiologicals analyzed (14.29%), and in 2023, the state of Minas Gerais stood out in this regard with a proportion of 20.54%. On the other hand, in 2022, 81.25% of the municipalities in Amapá had 0% homogeneity, and in 2023, 86.36% of the municipalities in Acre were classified as 0% (Table ). Regarding risk classification for the transmission of vaccine-preventable diseases, Brazil had 72.01% of municipalities classified as high or very high risk in 2022 and 65.13% in 2023. As for municipalities classified as low or very low risk, 11.27% were classified in this category in 2022 and 18.12% in 2023 (Table ). Table shows the final risk classification for the transmission of vaccine-preventable diseases by state and the Distrito Federal.In 2022, the state with the highest proportion of its municipalities classified as very low risk was Paraná (14.29%), followed by Minas Gerais (12.54%). In 2023, the highest proportion of municipalities at very low risk was Minas Gerais (20.52%), followed by Paraíba (18.83%). 

This study analyzed immunization indicators to assess the risk classification of Brazilian municipalities after implementing MP as a strategy for increasing vaccination coverage in 2023. There was an increase in median VC for all the vaccines evaluated except for the varicella vaccine. In 2023, the Ministry of Health implemented the MP methodology in Brazil to ensure that high-quality vaccination activities reach unvaccinated target populations10. Throughout the year, PM workshops were offered to states and municipalities to familiarize themselves with and adopt this strategy in their territories. For this purpose, the federal government provided funds for PM to be included and implemented in municipal and state health plans . MP involves surveying and mapping unvaccinated target populations, qualifying them, and understanding the reasons for non-vaccination, among other factors. This allows for the definition of appropriate strategies and planning for vaccines to reach these groups and be administered effectively . Therefore, MP is an important strategy for achieving high VC, involving a series of targeted actions that generate evidence after implementation. In 2022, the human rotavirus vaccine had the highest proportion of municipalities reaching the recommended target, followed by pneumococcal vaccines and the first dose of MMR. This trend continued in 2023. The second dose of the triple viral vaccine and the vaccine against yellow fever had the lowest percentage of municipalities reaching the coverage target in both years analyzed. The epidemiological situation of vaccine-preventable diseases in the country has undergone significant changes since the establishment of the National Immunization Program, as evidenced by polio control and the elimination of rubella, congenital rubella syndrome, and neonatal tetanus . The findings of this study regarding the improvement of VC are important, given that Brazil faces the risk of poliovirus reintroduction and is seeking to regain the certification of measles elimination lost in 2019. The Multivaccination Campaign9, which primarily aims to update the vaccination schedule of children and adolescents up to the age of 15, was launched in regional stages in the second half of 2023. This campaign is an example of the actions the National Movement for Vaccination took, which has certainly contributed to improving these rates. However, it is known that multi-dose vaccines are more likely to have a dropout rate, as seen with the second dose of the triple viral vaccine, for example. During times of vaccine hesitancy, there may be less refusal or fear of orally administered vaccines, such as polio and rotavirus, compared to injectable vaccines. The decision-making process regarding childhood vaccination is multifactorial and complex, and hesitancy has been identified as primarily driven by the perception of risk . Furthermore, many diseases that used to have a significant impact on morbidity and mortality have become unknown after eradication1. In several countries, there has been a reduction in achieving the recommended targets for vaccine coverage rates, especially in the last decade. One cause of this reduction is the increasing strength and presence of anti-vaccine movements in digital media. This is due to the ease of access and the growing influence of the internet and social networks in the lives of the population [ , , ]. The discontinuity of public health policies between 2019 and 2022 has discredited scientific evidence related to vaccines through the spread of fake news, unpreparedness in information dissemination, and discrediting immunization efforts. This has negatively impacted the country’s vaccination coverage . Additionally, this context has not only left a negative legacy for future generations regarding science denialism but has also weakened the National Immunization Program and hindered progress toward achieving high vaccination rates. These actions go against the principles of the Unified Health System. Reducing the abandonment rate of the multi-dose vaccine schedule in Brazilian municipalities  poses several challenges. Socio-economic and environmental factors impede equal access to vaccination centers, leading to a high abandonment rate of the multi-dose vaccination schedule . During the COVID-19 pandemic, vaccine administration was centralized in certain municipalities, making it difficult for the population to access them. Even after the emergency decree was lifted, some municipalities continued this practice. Implementing strategies such as increasing community-based vaccination campaigns could help ensure that vaccines reach communities that face difficulties accessing vaccination centers. Another crucial measure is actively searching for individuals who missed their vaccinations, particularly for multi-dose vaccines. Community health agents play a vital role in this regard, and it is essential to provide them with training and refresher courses due to their high turnover rate. The quality of home visits and adherence to scheduled visits are crucial for maintaining accurate vaccination records for all individuals across all life stages. Health education initiatives are also vital components of the work carried out by CHAs. With this in mind, in 2023, the Ministry of Health launched the booklet “The Community Health Agent: A Strong Ally in Improving Vaccination Coverage,” which provides comprehensive content on vaccines, searching for absentees, community mobilization, combating fake news, and more. The language used in the booklet is aimed at these professionals to directly support their training and updating to increase vaccination coverage . Braz et al. (2016)  found that only 32.5% of municipalities reached their polio vaccine targets in 2014. However, this study also demonstrates that Brazil has made progress in this area, which may be attributed to well-established campaigns of the polio control program featuring the beloved character Zé Gotinha, as well as the support of celebrities . Although there has been progress in classifying the risk of vaccine-preventable disease transmission among Brazilian municipalities, it is important to identify the states with the highest percentage of municipalities at high and very high risk. This will allow for targeted attention and intervention in these areas. Since there is a significant amount of turnover in Primary Health Care teams nationwide, and since immunization is a top priority in this service, it is necessary to promote surveillance of vaccination coverage in the territories. This includes monitoring the population to be vaccinated and keeping records of administered vaccine doses. Providing continuous training for teams on the use of the information system, emphasizing the importance of entering accurate and timely data, as well as ensuring the quality and consistency of the generated data, are crucial in achieving effective immunization of the population . For the vaccination program to be effective, it is essential for State and Municipal Health Secretariats to collaborate with various institutions and external partners. This collaboration should involve the formation of a strategic network between governmental and non-governmental organizations, Municipal Health Councils, community councils, and other collaborators . Promising initiatives to increase VC5,8 have been developed in various states across the country. One such initiative is the project “Strategies for Increasing Vaccination Coverage in Children Under 2 Years of Age in the State of Minas Gerais: An Action Research,”whose actions implemented by 212 surveyed municipalities have contributed to a statistically significant reduction (from 80.7 to 68.4%) in the percentage of municipalities classified as high and very high risk for the transmission of vaccine-preventable diseases when comparing 2021 with 2022 . Unfortunately, the country’s vaccination landscape will require more time and effort from the health sector and society to recover from the setbacks caused by the COVID-19 pandemic. The pandemic has kept the population away from health facilities and has contributed to an increase in vaccine hesitancy . Limitations of the study Data on the doses administered were obtained from TabNet/DATASUS and the National Health Data Network. The researchers had no control over the quality of the forms filled in by these systems. In addition, there is the possibility of underestimation or overestimation of the data due to flaws in the records of doses administered and also due to delays in updating population estimates, and the database is sensitive and subject to changes (both upwards and downwards) for various reasons, including corrections to records and corrections related to the database. However, it is important to note that these systems have a solid foundation, making it possible to support health strategies and policies by monitoring vaccination coverage in Brazil. Errors in recording vaccine doses in the system can also have a direct and negative impact on the immunization indicators analysed, increasing the number of municipalities at high and very high risk of disease transmission. 

Data on the doses administered were obtained from TabNet/DATASUS and the National Health Data Network. The researchers had no control over the quality of the forms filled in by these systems. In addition, there is the possibility of underestimation or overestimation of the data due to flaws in the records of doses administered and also due to delays in updating population estimates, and the database is sensitive and subject to changes (both upwards and downwards) for various reasons, including corrections to records and corrections related to the database. However, it is important to note that these systems have a solid foundation, making it possible to support health strategies and policies by monitoring vaccination coverage in Brazil. Errors in recording vaccine doses in the system can also have a direct and negative impact on the immunization indicators analysed, increasing the number of municipalities at high and very high risk of disease transmission. 

The surveillance of vaccination coverage and the Microplanning methodology for high-quality vaccination activities developed by the Ministry of Health in 2023 was an important ally in the resumption of immunization work, which had been hindered by the denial of science and the COVID-19 pandemic. The analysis of the immunization indicators of the 5,570 Brazilian municipalities in this study, based on the risk classification for vaccine-preventable diseases, can indicate which territories require greater attention after implementing the MP. This emphasizes the importance of risk classification for diagnosing and prioritizing municipalities that require intensified efforts by the Ministry of Health to prioritize actions to increase vaccination coverage. It also emphasizes the importance of projects and action plans to improve vaccination coverage, which have already been effectively developed by Brazilian states such as Minas Gerais and Paraíba, with the aim of achieving a scenario of high and uniform vaccination coverage in Brazil once again. Therefore, the Microplanning methodology for Avaq, developed by the Ministry of Health in 2023, has proven to be effective in improving immunization indicators, represented here by vaccination coverage, uniformity, and the drop-out rate for multi-dose vaccines. 

