Are the Objectives Proposed by the WHO for Routine Measles Vaccination Coverage and Population Measles Immunity Sufficient to Achieve Measles Elimination from Europe?

Pedro Plans-Rubió

doi:10.3390/vaccines8020218

Abstract

Background: The World Health Organization (WHO) proposed two-dose measles vaccination coverage of at least 95% of the population and percentages of measles immunity in the population of 85%−95% in order to achieve measles elimination in Europe. The objectives of this study were: (1) to determine the measles vaccination coverage required to establish herd immunity against measles viruses with basic reproduction numbers (Ro) ranging from 6 to 60, and (2) to assess whether the objectives proposed by the WHO are sufficient to establish herd immunity against measles viruses. Methods: The herd immunity effects of the recommended objectives were assessed by considering the prevalence of protected individuals required to establish herd immunity against measles viruses with Ro values ranging from 6 to 60. Results: The study found that percentages of two-dose measles vaccination coverage from 88% to 100% could establish herd immunity against measles viruses with Ro from 6 to 19, assuming 95% measles vaccination effectiveness. The study found that the objective of 95% for two-dose measles vaccination coverage proposed by the WHO would not be sufficient to establish herd immunity against measles viruses with Ro ≥ 10, assuming 95% measles vaccination effectiveness. By contrast, a 97% measles vaccination coverage objective was sufficient to establish herd immunity against measles viruses, with Ro values from 6 to 13. Measles immunity levels recommended in individuals aged 1−4 years (≥85%) and 5−9 years (≥90%) might not be sufficient to establish herd immunity against most measles viruses, while those recommended in individuals aged 10 or more years (≥95%) could be sufficient to establish herd immunity against measles viruses with Ro values from 6 to 20. Conclusion: To meet the goal of measles elimination in Europe, it is necessary to achieve percentages of two-dose measles vaccination coverage of at least 97%, and measles immunity levels in children aged 1−9 years of at least 95%.

Highlights

Measles is a highly contagious infectious disease associated with outbreaks, hospitalizations, and deaths in Europe, as well as in other regions of the world, despite highly effective vaccines being available
Herd immunity can be considered established when the prevalence of protected individuals is higher than the critical prevalence (I > Ic ), when the vaccination coverage is higher than the critical coverage (V > Vc ), and when the prevalence of positive serologic anti-measles results is higher than the critical prevalence (p > pc )
The critical prevalence of protected individuals (Ic ) associated with herd immunity ranged from 83.3% for measles viruses with reproduction numbers (Ro) = 6, to 98.3% for measles viruses with

Summary

Introduction

Measles is a highly contagious infectious disease associated with outbreaks, hospitalizations, and deaths in Europe, as well as in other regions of the world, despite highly effective vaccines being available. In 2015, the European Region of the World Health Organization (WHO) renewed their commitment to the elimination of measles by the year 2020 [1]. Vaccines 2020, 8, 218 the measles vaccine increased from 68% in 1995 to 91%−92% since 2004 [2]. The mean vaccination coverage with two doses of the measles vaccine increased from 58.6% in 1995 to 84%−88% since 2004 [2]. The World Health Organization (WHO) proposed two-dose measles vaccination coverage of at least 95% of the population and percentages of measles immunity in the population of. 85%−95% in order to achieve measles elimination in Europe. The objectives of this study were: (1) to determine the measles vaccination coverage required to establish herd immunity against measles viruses with basic reproduction numbers (Ro) ranging from 6 to 60, and (2) to assess whether the objectives proposed by the WHO are sufficient to establish herd immunity against measles viruses

Objectives

Methods

Results

Conclusion