Impact of Varicella Vaccination in the Population Under 10 Years in Minas Gerais: Comparison Between Pre- And Post-Vaccination Periods (2008–2023)

Varicella is a highly contagious disease caused by varicella-zoster virus, affecting mainly children. Although usually benign, it can cause severe complications in vulnerable populations. The tetravalent vaccine (measles, mumps, rubella and varicella) was introduced into the Programa Nacional de Imunizações in Brazil, within SUS, in 2013 as a control measure. Minas Gerais (MG), one of the most populous states, had high varicella notification rates prior to vaccine coverage expansion. This study aims to compare the pre- and post-vaccination periods (2008–2023) in the population under 10 years in the state Descriptive study with a quantitative approach, using data from the Sistema de Agravos de Notificação (SINAN) via TabNet. Confirmed varicella cases in children under 10 years in MG from 2008 to 2023 were analyzed. Variables included year of notification, age group, sex, self-declared race/skin color and outcome. Data were grouped into two periods: pre-vaccination (2008–2012) and post-vaccination (2014–2023), excluding 2013 as the year of tetravalent vaccine introduction. A total of 156,746 varicella cases were notified in children under 10 years in Minas Gerais during the period. From 2008 to 2012, there were 92,326 cases (58.9%), with a peak in 2010 (30,501 cases). From 2014 to 2023, 39,768 cases (25.4%) were recorded, showing a decline after vaccine introduction in 2013. The reduction was more marked from 2015 onward, with the lowest numbers in 2020 and 2021 (637 and 352 cases, respectively), though a slight increase was seen in 2022. The most affected age group was 1–4 years (79,716 cases; 50.8%). Regarding sex, cases predominated among males (81,479; 52%). Self-declared race/skin color was mostly white (58,554; 37.4%). Most cases evolved to cure (151,380; 96.6%), with 160 deaths directly attributed to varicella (0.1%) and 21 additional deaths due to other causes. The findings reinforce the effectiveness of vaccination in reducing varicella cases, demonstrating that low adherence to the vaccination schedule is directly associated with increased disease incidence. Furthermore, an increase in clinical complications related to varicella is observed in periods of lower vaccination coverage, as seen in 2022, when declining adherence coincided with a marked rise in notifications.