# Social inequalities and full vaccination coverage at 24 months – 2017-2018 live birth cohort: National Vaccination Coverage Survey, 2020

## TL;DR

This study found that vaccination coverage for 24-month-olds in Brazil is below 50% across all social strata, with the lowest rates in higher-income areas.

## Contribution

The study reveals unexpected lower vaccination rates in higher socioeconomic strata and identifies factors like family size and access to health services.

## Key findings

- Vaccination coverage was below 50% in all strata, with the lowest in strata A and B.
- Higher full immunization rates were linked to exclusive use of public health services.
- Family factors like crowding and multiple children reduced the likelihood of full vaccination.

## Abstract

To analyze social inequalities in vaccination coverage for the full immunization schedule with valid doses at 24 months of age, according to socioeconomic strata and family, maternal, and child characteristics.

This is a retrospective 2017–2018 live birth cohort in capitals, the Federal District, and 12 Brazilian cities, recruited in 2020–2021. Participants were followed up from birth using the vaccination cards, and there were no losses to follow-up. Guardians were interviewed and vaccination cards were photographed. Urban census tracts of the 39 cities were grouped into four strata by cluster analysis of average income, income >20 minimum wage, % literate individuals. The same number of census tracts were drawn from each stratum, and children from cohorts of interest were recruited until sample size was complete. The coverage of the full immunization schedule for each child was calculated considering only valid doses (date and interval between doses). Descriptive, stratified analysis, and Poisson regression were performed using the STATA 17.0 survey module.

A total of 37,801 children were included. Vaccination coverage was below 50% in all strata, with strata A and B as the lowest. The probability of having a full immunization schedule was lower from the second-born child onward, in families with intra-household crowding, and difficulties in accessing health services. Exclusive use of public services was associated with higher full coverage.

Vaccination coverage was lower in strata with better standards of living (A/B). Vaccination coverage by family, maternal, and individual factors vary between strata and it is not possible to establish a common pattern.

Analisar desigualdades sociais na cobertura vacinal para o esquema completo aos 24 meses de idade, doses válidas, segundo estratos socioecômicos e características familiares, maternas e da criança.

Coorte retrospectiva de nascidos vivos em 2017–2018 nas capitais; no Distrito Federal; e em 12 cidades brasileiras, recrutadas em 2020–2021, acompanhadas a partir do nascimento por meio da caderneta de vacinação, sem perdas de seguimento. Os responsáveis foram entrevistados e as cadernetas foram fotografadas. Os setores censitários urbanos das 39 cidades foram agrupados em 4 estratos por análise de cluster da renda média, renda>20 sm, %alfabetizados. Em cada estrato foram sorteados o mesmo número de setores, e as crianças das coortes de interesse foram recrutadas até completar-se o tamanho da amostra. A cobertura pelo esquema completo foi calculada para cada criança considerando doses válidas (data e intervalo entre doses). As análises descritiva, estratificada e de regressões de Poisson foram realizadas no módulo survey do STATA 17.0.

Foram incluídas 37.801 crianças. Coberturas ficaram abaixo de 50% em todos os estratos, sendo menores nos estratos A e B. A probabilidade de ter o esquema completo foi menor a partir do segundo filho em famílias com aglomeração intradomiciliar e dificuldades de acesso aos serviços. O uso exclusivo de serviços públicos foi associado à maior cobertura completa.

Coberturas vacinais foram menores nos estratos com melhores condições de vida (A/B). A cobertura vacinal segundo fatores familiares, maternos e individuais varia entre os estratos, não sendo possível estabelecer um padrão comum.