Impact of increased influenza vaccination in 2-3-year-old children on disease burden within the general population: A Bayesian model-based approach

PLoS One. 2017 Dec 15;12(12):e0186739. doi: 10.1371/journal.pone.0186739. eCollection 2017.

Abstract

Introduction: During the 2013-2014 influenza season, Public Health England extended routine influenza vaccination to all 2- and 3-year-old children in England. To estimate the impact of this change in policy on influenza-related morbidity and mortality, we developed a disease transmission and surveillance model informed by real-world data.

Methods: We combined real-world and literature data sources to construct a model of influenza transmission and surveillance in England. Data were obtained for four influenza seasons, starting with the 2010-2011 season. Bayesian inference was used to estimate model parameters on a season-by-season basis to assess the impact of targeting 2- and 3-year-old children for influenza vaccination. This provided the basis for the construction of counterfactual scenarios comparing vaccination rates of ~2% and ~35% in the 2- and 3- year-old population to estimate reductions in general practitioner (GP) influenza-like-illness (ILI) consultations, respiratory hospitalizations and deaths in the overall population.

Results: Our model was able to replicate the main patterns of influenza across the four seasons as observed through laboratory surveillance data. Targeting 2- and 3-year-old children for influenza vaccination resulted in reductions in the general population of between 6.2-9.9% in influenza-attributable GP ILI consultations, 6.1-10.7% in influenza-attributable respiratory hospitalizations, and 5.7-9.4% in influenza-attributable deaths. The decrease in influenza-attributable ILI consultations represents a reduction of between 4.5% and 7.3% across all ILI consultations. The reduction in influenza-attributable respiratory hospitalizations represents a reduction of between 1.2% and 2.3% across all respiratory hospitalizations. Reductions in influenza-attributable respiratory deaths represent a reduction of between 0.9% and 2.4% in overall respiratory deaths.

Conclusion: This study has provided evidence that extending routine influenza vaccination to all healthy children aged 2 and 3 years old leads to benefits in terms of reduced utilization of healthcare resources and fewer respiratory health outcomes and deaths.

MeSH terms

  • Adolescent
  • Adult
  • Aged
  • Bayes Theorem
  • Child
  • Child, Preschool
  • England / epidemiology
  • Epidemiological Monitoring
  • Female
  • Hospitalization / economics
  • Hospitalization / statistics & numerical data
  • Humans
  • Infant
  • Infant, Newborn
  • Influenza A Virus, H1N1 Subtype / immunology*
  • Influenza A Virus, H3N2 Subtype / immunology*
  • Influenza Vaccines / administration & dosage*
  • Influenza, Human / economics*
  • Influenza, Human / immunology
  • Influenza, Human / mortality
  • Influenza, Human / prevention & control*
  • Male
  • Mass Vaccination / methods*
  • Middle Aged
  • Office Visits / economics
  • Office Visits / statistics & numerical data
  • Seasons
  • Survival Analysis

Substances

  • Influenza Vaccines

Grants and funding

This study was supported by AstraZeneca. Sankarasubramanian Rajaram is a former employee of AstraZeneca; Richard Lawson, Betina Blak, Judith Hackett, and Robert Brody are employees of AstraZeneca; Yanli Zhao is an employee of MedImmune, the biologics arm of AstraZeneca. Witold Wiecek and Billy Amzal are employees of LASER Analytica who have received funding for the current study from AstraZeneca. Vishal Patel is a former employee of LASER Analytica. The funder provided support in the form of salaries for authors Betina Blak, Robert Brody, Judith Hackett, Richard Lawson, Yanli Zhao, and Sankarasubramanian Rajaram (during the time of the study when Sankarasubramanian Rajaram was employed by AstraZeneca) and funding to Laser Analytica to conduct the study. Members of AstraZeneca were permitted to review the manuscript and offer comments, but the authors decided whether or not to address these comments. Editorial support was provided by Sinead Stewart and Talya Underwood, MPhil (Cantab) of Prime Global, Knutsford, UK, funded by AstraZeneca, in accordance with Good Publication Practice guidelines (Link). AstraZeneca did not have any additional role in the study design, data collection and analysis, decision to publish, or preparation of the manuscript.