Measles Virus Infection and Immunity in a Suboptimal Vaccination Coverage Setting.

Monia Pacenti,Enrico Lavezzo,Luisa Barzon,Nataskya Maione,Elisa Franchin,Federico Dal Bello,Lorena Gottardello

doi:10.3390/vaccines7040199

Abstract

Despite efforts to improve surveillance and vaccination coverage, measles virus (MeV) continues to cause outbreaks also in high-income countries. As the reference laboratory of the Veneto Region, Italy, we analyzed changes in population immunity, described measles outbreaks, investigated MeV genetic diversity, and evaluated cross-protection of measles vaccination against MeV epidemic strains. Like most European areas, the Veneto Region has suboptimal measles vaccination coverage and is facing a growing public mistrust of vaccination. A progressive decline of measles vaccine uptake was observed during the last decade in the Veneto Region, leading to immunity gaps in children and young adults. Measles outbreaks were caused by the same MeV genotype B3, D4, and D8 strains that were circulating in other European countries. Eleven cases of measles were observed in immunized subjects. These cases were not associated with particular MeV genotypes nor with mutations in epitopes recognized by neutralizing antibodies. Accordingly, sera from fully vaccinated subjects cross-neutralized epidemic MeV strains, including the genotypes B3, D4, and D8, with the same high efficiency demonstrated against the vaccine strain. In fully vaccinated subjects, high MeV IgG antibody titers persisted up to 30 years following vaccination. These results support the use of the current measles-containing vaccines and strategies to strengthen vaccination.

Highlights

Despite efforts to improve surveillance and vaccination coverage, measles virus (MeV) continues to cause outbreaks in low-income and in high-income countries [1]
In line with the WorldHealth Organization (WHO) 2012–2020 Global Measles and Rubella Strategic Elimination Plan and the Midterm Review, which recommended research on susceptibility profiles for measles and research related to outbreaks in high-vaccine-coverage settings [12], the aim of this study was to investigate multiple aspects of measles infection and population immunity by an integrated analysis of field and experimental data obtained during the last decade in the Veneto Region, Italy, as a representative region in Europe
Decreased population immunity and low vaccine uptake due to hesitancy of the population toward vaccination represent key factors for the resurgence of measles epidemics in industrialized countries

Summary

Introduction

Despite efforts to improve surveillance and vaccination coverage, measles virus (MeV) continues to cause outbreaks in low-income and in high-income countries [1]. Among European countries, Romania, Italy, Greece, France, and the United Kingdom have been the most affected, all characterized by a vaccination coverage below the 95% target defined by WHO for measles elimination [3]. Vaccines 2019, 7, 199 sustain transmission during outbreaks, as recently predicted by a modelling analysis [6]. Another factor that has been hypothesized to account for the current resurge of measles is the emergence of new viral strains characterized by increased transmissibility and escape from vaccine-induced immunity [7]

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