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Heterogeneity in social and epidemiological factors determines the risk of measles outbreaks.

ABSTRACT: Political and environmental factors-e.g., regional conflicts and global warming-increase large-scale migrations, posing extraordinary societal challenges to policymakers of destination countries. A common concern is that such a massive arrival of people-often from a country with a disrupted healthcare system-can increase the risk of vaccine-preventable disease outbreaks like measles. We analyze human flows of 3.5 million (M) Syrian refugees in Turkey inferred from massive mobile-phone data to verify this concern. We use multilayer modeling of interdependent social and epidemic dynamics to demonstrate that the risk of disease reemergence in Turkey, the main host country, can be dramatically reduced by 75 to 90% when the mixing of Turkish and Syrian populations is high. Our results suggest that maximizing the dispersal of refugees in the recipient population contributes to impede the spread of sustained measles epidemics, rather than favoring it. Targeted vaccination campaigns and policies enhancing social integration of refugees are the most effective strategies to reduce epidemic risks for all citizens.

SUBMITTER: Bosetti P

PROVIDER: S-EPMC7720222 | biostudies-literature | 2020 Dec

REPOSITORIES: biostudies-literature

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Heterogeneity in social and epidemiological factors determines the risk of measles outbreaks.

Bosetti Paolo P Poletti Piero P Stella Massimo M Lepri Bruno B Merler Stefano S De Domenico Manlio M

Proceedings of the National Academy of Sciences of the United States of America 20201117 48

Political and environmental factors-e.g., regional conflicts and global warming-increase large-scale migrations, posing extraordinary societal challenges to policymakers of destination countries. A common concern is that such a massive arrival of people-often from a country with a disrupted healthcare system-can increase the risk of vaccine-preventable disease outbreaks like measles. We analyze human flows of 3.5 million (M) Syrian refugees in Turkey inferred from massive mobile-phone data to ve ...[more]

PMID: 33203683

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Project description:BackgroundAge-stratified serologic surveys provide insight into the gaps of measles-specific immunity as well as estimates of the age-specific seroprevalence. The aim of this study was to describe the measles sero-epidemiology in Vojvodina before the occurrence of outbreak in 2017/18 and to discuss preventive measures for potential future epidemics.MethodsA seroprevalence study was conducted from April 2015 to June 2017 on serum bank of 3199 residual samples. Study was performed prior to the last measles outbreak in Vojvodina that occurred between 12th November 2017 and 30th June 2018. Measles-specific IgG antibodies were determined using an indirect chemiluminescent immunoassay (CLIA).ResultsMedian age of enrolled participants was 20 years (IQR 11-37). Overall, 86.9% serum samples were seropositive. The highest proportion of measles seronegativity was observed in children aged 12-23 months of age and in adults aged 20-39 years (56.1% and 18.5%, respectively). Prevalence of measles seronegativity above WHO target levels susceptibility was observed in the following age groups: 2, 7, 13, 15, and among all adults aged between 20 and 49 years. Out of total measles outbreak cases (177), there were 91 (51.4%) participants aged 20-39 years. A significant positive correlation was observed between measles seronegativity and the number of reported measles cases aged ≥ 12 months (r = 0.4675, p = 0.0213).ConclusionsIn order to prevent new outbreaks and achieve the elimination of measles in Vojvodina, the vaccination coverage of both measles-mumps-rubella (MMR1 and MMR2) vaccines needs to be improved and sustained. Educational campaigns for the improvement of acceptance and timely vaccination with vaccine against measles among doctors and the general population are crucial. Our results indicate possible gap in measles protection in adults born during implementation of one dose of measles vaccine and prioritize supplementary immunization activities targeting adults in Vojvodina, Serbia.

Project description:BackgroundVaccination programmes to prevent outbreaks after introductions of infectious people aim to maintain the average number of secondary infections per infectious person at one or less. We aimed to assess heterogeneity in vaccine uptake and other characteristics that, together with non-random mixing, could increase this number and to evaluate strategies that could mitigate their impact.MethodsBecause most US children attend elementary school in their own neighbourhoods, surveys of children entering elementary school (age 5 years before Sept 1) allow assessment of spatial heterogeneity in the proportion of children immune to vaccine-preventable diseases. We used data from a 2008 school-entry survey by the Immunization Division of the California Department of Public Health to obtain school addresses; numbers of students enrolled; proportions of enrolled students who had received one or two doses of the measles, mumps, and rubella (MMR) vaccine; and proportions with medical or personal-belief exemptions. Using a mixing model suitable for spatially-stratified populations, we projected the expected numbers of secondary infections per infectious person for measles, mumps, and rubella. We also mapped contributions to this number for measles in San Diego County's 638 elementary schools and its largest district, comprising 200 schools (31%). We then modelled the effect on measles' realised reproduction number (RV) of the following plausible interventions: vaccinating all children with personal-belief exemptions, increasing uptake by 10% to 50% in all low-immunity schools (<90% of students immune) or in only influential (effective daily contact rates >3 or contacts inter-school >30%) low-immunity schools, and increasing private school uptake to the public school average.FindingsIn 2008, 39 132 children began elementary school in San Diego County, CA, USA. At entry to school, 97% had received at least one dose of the MMR vaccine, with 2·5% having personal-belief exemptions. We note substantial heterogeneity in immunity throughout the county. Although the average population immunities for measles, mumps, and rubella (92%, 87%, 92%) were similar to the population-immunity thresholds in homogeneous, randomly-mixing populations (91%, 88%, 76%), after accounting for heterogeneity and non-random mixing, the basic reproduction numbers increased by 70%, meaning that introduced pathogens could cause outbreaks. The impact of our modelled interventions ranged from negligible to a nearly complete reduction in the outbreak potential of measles. The most effective intervention to lower the realised reproduction number (RV 3·39) was raising immunity by 50% in 114 schools with low immunity (RV 1·02), but raising immunity by this level in only influential, low-immunity schools also was effective (RV 2·02). The effectiveness of vaccinating the 972 children with personal-belief exemptions was similar to that of targeting all low-immunity schools (RV 1·11). Targeting only private schools had little effect.InterpretationOur findings suggest that increasing vaccine uptake could prevent outbreaks such as that of measles in San Diego in 2008. Vaccinating children with personal-belief exemptions was one of the most effective interventions that we modelled, but further research on mixing in heterogeneous populations is needed.FundingNone.

Project description:BackgroundAlthough a universal vaccine is available and Ethiopia is working outstandingly towards measles elimination, a recurrent measles outbreak has occurred each year in different parts of the country. Therefore, understanding the epidemiology of measles cases, the incidence of confirmed measles virus cases and related risk factors is crucial. Here, we conducted a systematic review and meta-analysis to summarize information regarding the epidemiology, measles incidence rate and risk factors for national measles infections occurring in the past two decades, from 2000 to 2023.MethodsData from electronic databases, including PubMed, African Journal Online, WHO databases and Google Scholars, were searched to identify studies describing measles outbreaks, incidence rates and associated factors in Ethiopia that occurred between 2000 and 2023. Important basic information was extracted in an Excel spreadsheet and imported into Comprehensive Meta-analysis Software version 3 to evaluate the associations between measles outbreaks and different risk factors. We pooled the odds ratios (ORs) and 95% confidence intervals (CIs) for every included risk factor to evaluate the associations with measles outbreaks.ResultsWe included 36 studies involving 132,502 patients with confirmed measles cases in Ethiopia. The results of this systematic review and meta-analysis revealed that measles outbreaks were more frequently reported in the Oromia region (73,310 (33.1%)), followed by the Southern Nation Nationalities of Ethiopia region (29,057 (13.4%)). The overall pooled analysis indicated that the prevalence of measles susceptibility was 67.5% (95% CI: 67.3-67.8%), with an I2 of 99.86% and a p value for heterogeneity < 0.0001. The non-vaccinated status of the children, their contact history with measles cases, their travel history, the presence of cases in family or neighbors, and malnourished patients were identified as factors associated with the high prevalence and recurrent measles infections in Ethiopia.ConclusionThe results of this systematic review and meta-analysis indicated that the pooled prevalence of measles infection was high, which is a public health concern in Ethiopia. Thus, strengthening healthcare services, regular vaccination campaigns, and the integration of health education activities with other services may decrease the incidence rate.

Project description:BackgroundCase fatality ratio (CFR) among all age groups during the 2016-2018 measles outbreak in Romania was increased compared with previous outbreaks. To identify risk factors for measles death, we conducted a case-control study among infants and children hospitalized for measles.MethodsNational surveillance data were used to identify hospitalized cases of laboratory-confirmed or epidemiologically linked measles in infants and children aged < 59 months with rash onset from January 2016 to July 2018. We abstracted medical records of 50 fatal cases ("cases") and 250 non-fatal cases ("controls") matched by age, sex, district of residence, and urban/rural place of residence. We calculated univariable and multivariable matched odds ratios (OR) and 95% confidence intervals (CIs) for risk factors.ResultsNinety-three percent of case-patients and controls had not received a valid dose of a measles-containing vaccine; only 5 % received Vitamin A supplementation once diagnosed with measles. In the univariable analysis, cases were more likely than controls to have had a healthcare-related exposure to measles manifesting as inpatient admission for pneumonia during the 7 to 21 day measles incubation period (OR: 3.0; 95% CI [1.2, 7.2]), to have had a history of malnutrition (OR: 3.4; 95% CI [1.1, 9.9]), and to have had pneumonia as a complication of measles (OR:7.1; 95% CI [2.0-24.8]). In the multivariable analysis, pneumonia as a measles complication remained a risk for death (OR: 7.1; 95% CI [1.4-35.3]).ConclusionsImplementing infection prevention and control practices, ensuring immunization of healthcare workers, and hospitalizing only severe measles cases may minimize the risk of nosocomial measles transmission. Implementing World Health Organization (WHO) recommendations for Vitamin A supplementation, improving immunization of children to prevent influenza, pneumococcal, and other bacterial respiratory diseases may decrease complications and deaths due to measles in Romania.

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Heterogeneity in social and epidemiological factors determines the risk of measles outbreaks.

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Heterogeneity in social and epidemiological factors determines the risk of measles outbreaks.

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