{
  "abstract": "Objective\n\nVaricella (chickenpox) is a highly contagious disease, and its vaccine was incorporated into the Brazilian National Immunization Program in 2013. Objectives: (i) To analyze trends in hospitalization rates for severe chickenpox by age; (ii) To assess the impact of the interventions \"anti-vaccine movement/vaccine hesitancy\" and \"COVID-19 pandemic\" on hospitalization rates.Materials and methods\n\nClassical Time Series (CTS) and Interrupted Time Series (ITS) methods were applied to estimate the impact of the anti-vaccine movement/vaccine hesitancy (intervention-1) that occurred in 2016 and the COVID-19 pandemic (intervention-2) that began in 2020 on hospitalization rates among children under 5 years old, stratified by groups based on vaccine-ineligible (< 1 year old) and vaccine-eligible (1-4 years old) children.Results\n\nCTS results supported the potential for herd immunity effects, showing an annual decline of -17% and -14% in hospitalization rates for vaccine-eligible (1-4 years) and vaccine-ineligible (< 1 year) groups, respectively. The ITS model for vaccine-ineligible children showed an upward trend (coefficient 0.35) after intervention-1(isolate) (p=0.001), as well as after intervention-1 (coefficient 0.42; p 0.011) adjusting for intervention-2 (p=0.135). For vaccine-eligible children, the ITS model revealed an upward trend (coefficient 0.14) only after intervention-1 (isolate) (p=0.006).Conclusion\n\nThe decline in varicella hospitalizations indicates a herd immunity effect among vaccine-ineligible children. ITS analysis reveals that the anti-vaccine movement/vaccine hesitancy contributed to increased hospitalizations in both vaccine-eligible (1-4 years) and vaccine-ineligible (<1 year) groups, while the COVID-19 pandemic had no discernible impact.",
  "abstract_shown": true,
  "affiliations": [
    "Department of General and Specialized Surgery, Postgraduate Maternal Child Health Program, Faculty of Medicine, Fluminense Federal University, Niterói, Rio de Janeiro, Brazil.",
    "Faculty of Medicine, Fluminense Federal University, Niterói, Rio de Janeiro, Brazil.",
    "Postgraduate Maternal Child Health Program, Fluminense Federal University, Niterói, Rio de Janeiro, Brazil."
  ],
  "article_type": "research article",
  "arxiv": null,
  "author_total": 5,
  "authors": [
    {
      "affs": [
        0
      ],
      "name": "Maria Isabel do Nascimento"
    },
    {
      "affs": [
        1
      ],
      "name": "Alcenir Tavares Valente Junior"
    },
    {
      "affs": [
        1
      ],
      "name": "Beatriz de Vasconcelos Falcão"
    },
    {
      "affs": [
        1
      ],
      "name": "Marina Pereira da Silva"
    },
    {
      "affs": [
        2
      ],
      "name": "Mauricio Souza Leão"
    }
  ],
  "bibtex": "https://research.draconitic.com/paper/d1eb2hsrahqff.bib",
  "cited_by": 0,
  "doi": "10.18502/jfrh.v20i2.22614",
  "fulltext_url": "https://europepmc.org/articles/PMC13690109",
  "id": "d1eb2hsrahqff",
  "issns": [
    "1735-8949",
    "1735-9392"
  ],
  "landing_url": "https://europepmc.org/article/MED/42923831",
  "language": "eng",
  "licence": "CC-BY-NC",
  "licence_label": "CC BY-NC",
  "licence_source": "article",
  "licence_url": "https://creativecommons.org/licenses/by-nc/4.0/",
  "metadata_licence": null,
  "native_subjects": [
    [
      "openalex",
      "2713|Herpesvirus Infections and Treatments"
    ]
  ],
  "openalex": "W7212358173",
  "pdf_url": "https://europepmc.org/articles/PMC13690109?pdf=render",
  "pmcid": "PMC13690109",
  "pmid": "42923831",
  "published": "2026-06-01",
  "publisher": null,
  "ris": "https://research.draconitic.com/paper/d1eb2hsrahqff.ris",
  "sources": [
    {
      "first_seen": "2026-10-30T12:21:02Z",
      "native_id": "MED:42923831",
      "source": "europepmc",
      "url": "https://europepmc.org/article/MED/42923831"
    }
  ],
  "subjects": [
    {
      "field": "medicine",
      "origin": "openalex:2713|Herpesvirus Infections and Treatments",
      "subfield": "epidemiology-public-health"
    }
  ],
  "title": "Severe Varicella in Children Under Five Years of Age in the Context of Herd Immunity, Vaccine Hesitancy, and the COVID-19 Pandemic in Brazil, 2008-2023.",
  "title_text": "Severe Varicella in Children Under Five Years of Age in the Context of Herd Immunity, Vaccine Hesitancy, and the COVID-19 Pandemic in Brazil, 2008-2023.",
  "type": "peer-reviewed",
  "updated_at": "2026-10-30T12:21:02Z",
  "url": "https://research.draconitic.com/paper/d1eb2hsrahqff",
  "venue": "Journal of family & reproductive health",
  "versions": []
}