Identifying immunity gaps for measles using Belgian serial serology data

Vaccine-preventable diseases, such as measles, have been re-emerging in countries with moderate to high vaccine uptake. It is increasingly important to identify and close immunity gaps and increase coverage of routine childhood vaccinations, including two doses of the measles-mumps-rubella vaccine (MMR). Here, we present a simple cohort model relying on a Bayesian approach to evaluate the evolution of measles seroprevalence in Belgium using the three most recent cross-sectional serological survey data collections (2002, 2006 and 2013) and information regarding vaccine properties. We find measles seroprevalence profiles to be similar for the different regions in Belgium. These profiles exhibit a drop in seroprevalence in birth cohorts that were offered vaccination at suboptimal coverages in the first years after routine vaccination has been started up. This immunity gap is observed across all cross-sectional survey years, although it is more pronounced in survey year 2013. At present, the COVID-19 pandemic could negatively impact the immunization coverage worldwide, thereby increasing the need for additional immunization programs in groups of children that are impacted by this. Therefore, it is now even more important to identify existing immunity gaps and to sustain and reach vaccine-derived measles immunity goals.

A competing-risks model explains hierarchical spatial coupling of measles epidemics en route to national elimination

Apart from its global health importance, measles is a paradigm for the low-dimensional mechanistic understanding of local nonlinear population interactions. A central question for spatio-temporal dynamics is the relative roles of hierarchical spread from large cities to small towns and metapopulation transmission among local small population clusters in measles persistence. Quantifying this balance is critical to planning the regional elimination and global eradication of measles. Yet, current gravity models do not allow a formal comparison of hierarchical versus metapopulation spread. We address this gap with a competing-risks framework, capturing the relative importance of competing sources of reintroductions of infection. We apply the method to the uniquely spatio-temporally detailed urban incidence dataset for measles in England and Wales, from 1944 to the infection's vaccine-induced nadir in the 1990s. We find that despite the regional influence of a few large cities (for example, London and Liverpool), metapopulation aggregation in neighbouring towns and cities played an important role in driving national dynamics in the prevaccination era. As vaccination levels increased in the 1970s and 1980s, the signature of spatially predictable spread diminished: increasingly, infection was introduced from unidentifiable random sources possibly outside regional metapopulations. The resulting erratic dynamics highlight the challenges of identifying shifting sources of infection and characterizing patterns of incidence in times of high vaccination coverage. More broadly, the underlying incidence and demographic data, accompanying this paper, will also provide an important resource for exploring nonlinear spatiotemporal population dynamics.

Ongoing measles outbreak in Wallonia, Belgium, December 2016 to March 2017: characteristics and challenges

We describe characteristics of an ongoing measles outbreak in Wallonia, Belgium, and difficulties in control measures implementation. As at 12 March 2017, 177 measles cases were notified, of which 50% were 15 years and older, 49% female. Atypical clinical presentation and severe complications, mainly among adults, in combination with late notification, low or unknown vaccination coverage of contacts, infected healthcare workers and increased workload due to contact tracing, are the main concerns for outbreak management.

Different measles outbreaks in Belgium, January to June 2016 - a challenge for public health

During the first half of 2016, several outbreaks of measles were reported in the three regions of Belgium. Main challenges for public health were severe complications occurring in adults, nosocomial transmission and infection in healthcare workers. Here, we describe those outbreaks and lessons learnt for public health.

Assessing mumps outbreak risk in highly vaccinated populations using spatial seroprevalence data

Mumps is a potentially severe viral infection. The incidence of mumps has declined dramatically in high-income countries since the introduction of mumps antigen-containing vaccines. However, recent large outbreaks of mumps in highly vaccinated populations suggest waning of vaccine-induced immunity and primary vaccine failure. In this paper we present a simple method for identifying geographic regions with high outbreak potential, demonstrated using 2006 mumps seroprevalence data from Belgium and Belgian vaccination coverage data. Predictions of the outbreak potential in terms of the effective reproduction number in future years signal an increased risk of new mumps outbreaks. Literature reviews on serological information for both primary vaccine failure and waning immunity provide essential information for our predictions. Tailor-made additional vaccination campaigns would be valuable for decreasing local pockets of susceptibility, thereby reducing the risk of future large-scale mumps outbreaks.

Adult patients hospitalized for measles in France, in the 21st century

BACKGROUND

An epidemic of measles broke out in France in 2008. We designed a retrospective study focusing on adults hospitalized for measles in 2010/2011.

METHODS

A case was any patient aged more than 15 years, hospitalized (September 2010 to September 2011) with a typical rash or a biological diagnosis. Data was collected with standardized questionnaires in participating hospitals.

RESULTS

Four hundred and sixty cases were reported: sex-ratio (M/F) = 0.93, median age 26 years (σ = 8.8). Twenty-nine cases were severe (6.5%), 27 of which hospitalized in an ICU. Three hundred and twelve (68%) cases had elevated serum transaminases (EST), 155 (34%) cases had pneumonia, 34 (7%) cases had elevated serum creatinine (ESC), four (0.9%) cases had elevated serum amylase and lipase (ESAL), and three (0.7%) cases had neurological symptoms. One hundred and four (23%) patients presented simultaneously with EST and pneumonia. One patient presenting with severe pneumonia died (0.2%). One hundred and ten (24%) patients received antibiotics during a median seven days.

CONCLUSION

Measles can present as various syndromes in adults and be responsible for a high burden during outbreaks. The immediate outcome is favorable in most patients. Long-term outcome needs further investigations to identify possible late complications.

Obstacles in measles elimination: an in-depth description of a measles outbreak in Ghent, Belgium, spring 2011

Background

From Mid-February to April 2011 one of the largest measles-outbreak in Flanders, since the start of the 2-dose vaccination scheme in 1995, took place in Ghent, Belgium. The outbreak started in a day care center, infecting children too young to be vaccinated, after which it spread to anthroposophic schools with a low measles, mumps and rubella vaccination coverage. This report describes the outbreak and evaluates the control measures and interventions.

Methods

Data collection was done through the system of mandatory notification of the public health authority. Vaccination coverage in the schools was assessed by a questionnaire and the electronic immunization database ‘Vaccinnet’. A case was defined as anyone with laboratory confirmed measles or with clinical symptoms and an epidemiological link to a laboratory confirmed case. Towards the end of the outbreak we only sought laboratory confirmation for persons with an atypical clinical presentation or without an epidemiological link. In search for an index patient we determined the measles IgG level of infants from the day care center.

Results

A total of 65 cases were reported of which 31 were laboratory confirmed. Twenty-five were confirmed by PCR and/or IgM. In 6 infants, too young to be vaccinated, only elevated measles IgG levels were found. Most cases (72%) were young children (0–9 years old). All but two cases were completely unimmunized. In the day care center all the infants who were too young to be vaccinated (N=14) were included as cases. Thirteen of them were laboratory confirmed. Eight of these infants were hospitalized with symptoms suspicious for measles. Vaccination coverage in the affected anthroposophic schools was low, 45-49% of the pupils were unvaccinated. We organized vaccination campaigns in the schools and vaccinated 79 persons (25% of those unvaccinated or incompletely vaccinated).

Conclusions

Clustering of unvaccinated persons, in a day care center and in anthroposophic schools, allows for measles outbreaks and is an important obstacle for the elimination of measles. Isolation measures, a vacation period and an immunization campaign limited the spread of measles within the schools but could not prevent further spread among unvaccinated family members. It was necessary to raise clinicians' awareness of measles since it had become a rare, less known disease and went undiagnosed.

Measles outbreak in Europe: susceptibility of infants too young to be immunized

As women vaccinated against measles transfer low amounts of antibodies, an increasing number of infants lack early protection through maternal antibodies until being immunised themselves. This paper reviews the literature on disease burden of measles in the population too young to be immunized according to the respective national recommendations during recent outbreaks in EU and EEA/EFTA countries. In addition, specific control strategies adopted to protect this young population are reviewed. Pubmed, Unbound Medline, Web of Knowledge and the Eurosurveillance database were searched using MESH terms: measles and epidemiology, measles and infants, prevalence of measles, measles and outbreaks and measles and epidemic. Additionally, data from Euvac.net and ECDC were consulted. Databases were searched from January 2001 to September 2011. Fifty-three papers were included in the analysis. The percentage of all measles cases during outbreaks affecting young infants ranged from 0.25% to 83.0%. Specific control strategies were adopted: e.g. administration of the first or second vaccine dose earlier than recommended. Infants younger than 12 months are often involved in measles outbreaks, and advancing the first vaccine dose could reduce the burden of disease. However, immunization before 9 months of age is not systematically recommended because of dysmature humoral immune responses of infants. High coverage and timely administration of the recommended series of vaccines are the most important measures to decrease measles incidence and measles circulation and protect vulnerable infants from infection.