Introducing a novel model to estimate national and global measles disease burden

Measles and Rubella Elimination in the Western Pacific Region in 2013-2022: Lessons Learned from Progress and Achievements Made during Regional and Global Measles Resurgences

Measles is the most contagious communicable disease, causing an estimated 5.5 million cases and more than 30,000 deaths in the Western Pacific Region (WPR) during 2000. Rubella infection in a pregnant woman can be devastating for the foetus, resulting in congenital rubella syndrome (CRS) in 90% of rubella infections in early pregnancy. It was estimated that approximately 9000 CRS cases occurred in the WPR in 2010. World Health Organization (WHO) Member States in the WPR decided in 2003 to eliminate measles and in 2014 to eliminate rubella from the region. While the WPR successfully attained historically low measles incidence in 2012, it experienced a region-wide measles resurgence in 2013-2016. During the regional resurgence, WHO and Member States accumulated greater knowledge on the epidemiology of measles and rubella in the WPR and strategies to maintain gains. The implementation of the resulting new regional strategy and plan of action from 2018 has proven that measles and rubella elimination is achievable and sustainable under the pressure of multiple importations of measles virus during the world-wide measles resurgences in 2018-2019. This article discusses this progress and achievements towards achieving the global eradication of measles and rubella.

Evolution and Use of Dynamic Transmission Models for Measles and Rubella Risk and Policy Analysis

The devastation caused by periodic measles outbreaks motivated efforts over more than a century to mathematically model measles disease and transmission. Following the identification of rubella, which similarly presents with fever and rash and causes congenital rubella syndrome (CRS) in infants born to women first infected with rubella early in pregnancy, modelers also began to characterize rubella disease and transmission. Despite the relatively large literature, no comprehensive review to date provides an overview of dynamic transmission models for measles and rubella developed to support risk and policy analysis. This systematic review of the literature identifies quantitative measles and/or rubella dynamic transmission models and characterizes key insights relevant for prospective modeling efforts. Overall, measles and rubella represent some of the relatively simplest viruses to model due to their ability to impact only humans and the apparent life-long immunity that follows survival of infection and/or protection by vaccination, although complexities arise due to maternal antibodies and heterogeneity in mixing and some models considered potential waning immunity and reinfection. This review finds significant underreporting of measles and rubella infections and widespread recognition of the importance of achieving and maintaining high population immunity to stop and prevent measles and rubella transmission. The significantly lower transmissibility of rubella compared to measles implies that all countries could eliminate rubella and CRS by using combination of measles- and rubella-containing vaccines (MRCVs) as they strive to meet regional measles elimination goals, which leads to the recommendation of changing the formulation of national measles-containing vaccines from measles only to MRCV as the standard of care.

Impact of measles national vaccination coverage on burden of measles across 29 Member States of the European Union and European Economic Area, 2006-2011

BACKGROUND

Challenges in reaching good vaccination coverage against measles emerged in several European Union/European Economic Area Member States (EU/EEA MS) leading to progressive accumulation of susceptible individuals and outbreaks. The Burden of Communicable Diseases in Europe (BCoDE) project developed a methodology for measuring the burden of communicable diseases expressed in Disability-Adjusted Life Years (DALYs) in the EU/EEA MS. The aim of this study was to compare national vaccination coverage and burden of measles across EU/EEA MS.

METHODS

Country-specific data on measles national vaccination coverage 2006-2011 from 29 EU/EEA MS (MCV1) were retrieved from Centralized Information System for Infectious Diseases (CISID). DALYs were calculated for each country separately using a disease progression model with a single input parameter (annual measles incidence, adjusted for under-estimation). A software application was used to compute estimated DALYs according to country-specific and year-specific population age-distributions (data retrieved from Eurostat). Log-linear mixed-effect regression modeling approach was used to investigate a linear relation between natural logarithm-transformed DALYs and coverage.

RESULTS

The reported annual vaccination coverage ranged from 72.6% to 100%. The estimated national annual burden ranged from 0 to 30.6 DALYs/100,000. Adjusting for year, there was a significant negative relationship between coverage and burden. For a given country there was a decrease in log-transformed DALYs/100,000 of 0.025 (95% confidence interval: -0.047 to -0.003) for every percentage increase in vaccination coverage. The largest effect of calendar time on estimated burden of measles was observed for the year 2011, the smallest was for the year 2007.

CONCLUSIONS

This study shows that the degree of success of national measles vaccination programs, when measured by the coverage obtained, is significantly associated with overall impact of measles across EU/EEA MS. In EU/EEA MS each percentage point increase in national vaccination coverage seems to lead to early significant reduction of overall burden of measles.

Comparison of LiST measles mortality model and WHO/IVB measles model

BACKGROUND

The Lives Saved Tool (LiST) has been developed to estimate the impact of health interventions and can consider multiple interventions simultaneously. Given its increasing usage by donor organizations and national program planner, we compare the LiST measles model to the widely used World Health Organization's Department of Immunization, Vaccines and Biologicals (WHO/IVB) measles model which is used to produce estimates serving as a major indicator of monitoring country measles epidemics and the progress of measles control.

METHODS

We analyzed the WHO/IVB models and the LiST measles model and identified components and assumptions held in each model. We contrasted the important components, and compared results from the two models by applying historical measles containing vaccine (MCV) coverages and the default values of all parameters set in the models. We also conducted analyses following a hypothetical scenario to understand how both models performed when the proportion of population protected by MCV declined to zero percent in short time period.

RESULTS

The WHO/IVB measles model and the LiST measles model structures differ: the former is a mixed model which applies surveillance data adjusted for reporting completeness for countries with good disease surveillance system and applies a natural history model for countries with poorer disease control program and surveillance system, and the latter is a cohort model incorporating country-specific cause-of-death (CoD) profiles among children under-five. The trends of estimates of the two models are similar, but the estimates of the first year are different in most of the countries included in the analysis. The two models are comparable if we adjust the measles CoD in the LiST to produce the same baseline estimates. In addition, we used the models to estimate the potential impact of stopping using measles vaccine over a 7-year period. The WHO/IVB model produced similar estimates to the LiST model with adjusted CoD. But the LiST model produced low estimates for countries with very low or eliminated measles infection that may be inappropriate.

CONCLUSIONS

The study presents methodological and quantitative comparisons between the WHO/IVB and the LiST measles models that highlights differences in model structures and may help users to better interpret and contrast estimates of the measles death from the two models. The major differences are resulted from the usage of case-fatality rate (CFR) in the WHO/IVB model and the CoD profile in the LiST. Both models have their own advantages and limitations. Users should be aware of the issue and apply as update country parameters as possible. Advanced models are expected to validate the policy-planning tools in the future.

An Economic Analysis of the Current Universal 2-dose measles-mumps-rubella Vaccination Program in the United States

To evaluate the economic impact of the current 2-dose measles-mumps-rubella (MMR) vaccination program in the United States, a decision tree-based analysis was conducted with population-based vaccination coverage and disease incidence data. All costs were estimated for a hypothetical US birth cohort of 3803295 infants born in 2001. The 2-dose MMR vaccination program was cost-saving from both the direct cost and societal perspectives compared with the absence of MMR vaccination, with net savings (net present value) from the direct cost and societal perspectives of US dollars 3.5 billion and US dollars 7.6 billion, respectively. The direct and societal benefit-cost ratios for the MMR vaccination program were 14.2 and 26.0. Analysis of the incremental benefit-cost of the second dose showed that direct and societal benefit-cost ratios were 0.31 and 0.49, respectively. Varying the proportion of vaccines purchased and administered in the public versus the private sector had little effect on the results. From both perspectives under even the most conservative assumptions, the national 2-dose MMR vaccination program is highly cost-beneficial and results in substantial cost savings.

Combating tropical infectious diseases: report of the Disease Control Priorities in Developing Countries Project

Infectious diseases are responsible for >25% of the global disease toll. The new Disease Control Priorities in Developing Countries Project (DCPP) aims to decrease the burden of these diseases by producing science-based analyses from demographic, epidemiologic, disease intervention, and economic evidence for the purpose of defining disease priorities and implementing control measures. The DCPP recently reviewed selected tropical infectious diseases, examined successful control experiences, and defined unsettled patient treatment, prevention, and research issues. Disease elimination programs against American trypanosomiasis (Chagas disease), onchocerciasis, lymphatic filariasis, leprosy, trachoma, and measles are succeeding. Dengue, leishmaniasis, African trypanosomiasis, malaria, diarrheal diseases, helminthic infections, and tuberculosis have reemerged because of inadequate interventions and control strategies and the breakdown of health delivery systems. Application of technologies must be cost-effective and intensified research is essential if these and other scourges are to be controlled or eliminated in the 21st century.

Predicting the distribution of under-five deaths by cause in countries without adequate vital registration systems

BACKGROUND

The absence of complete vital registration and atypical nature of the locations where epidemiological studies of cause of death in children are conducted make it difficult to know the true distribution of child deaths by cause in developing countries. A credible method is needed for generating valid estimates of this distribution for countries without adequate vital registration systems.

METHODS

A systematic review was undertaken of all studies published since 1980 reporting under-5 mortality by cause. Causes of death were standardized across studies, and information was collected on the characteristics of each study and its population. A meta-regression model was used to relate these characteristics to the various proportional mortality outcomes, and predict the distribution in national populations of known characteristics. In all, 46 studies met the inclusion criteria.

RESULTS

Proportional mortality outcomes were significantly associated with region, mortality level, and exposure to malaria; coverage of measles vaccination, safe delivery care, and safe water; study year, age of children under surveillance, and method used to establish definitive cause of death. In sub-Saharan Africa and in South Asia, the predicted distribution of deaths by cause was: pneumonia (23% and 23%), malaria (24% and <1%), diarrhoea (22% and 23%), 'neonatal and other' (29% and 52%), measles (2% and 1%).

CONCLUSIONS

For countries without adequate vital registration, it is possible to estimate the proportional distribution of child deaths by cause by exploiting systematic associations between this distribution and the characteristics of the populations in which it has been studied, controlling for design features of the studies themselves.

The global burden of measles in the year 2000--a model that uses country-specific indicators

The estimation of the global burden of measles is challenging in the absence of reliable and comparable surveillance systems worldwide. A static model is described that enables estimation of measles morbidity, mortality, and disability for the year 2000 on the basis of country-specific information (i.e., demographic profile, vaccine coverage, and estimates of case-fatality ratios). This approach estimated a global incidence of 39.9 million measles cases, 777,000 deaths, and 28 million disability-adjusted life years. The World Health Organization regions of Africa and Southeast Asia had 70% of incident cases and 84% of measles-related deaths; 11 countries alone (Afghanistan, Burkina Faso, Democratic Republic of the Congo, Ethiopia, India, Indonesia, Niger, Nigeria, Pakistan, Somalia, Uganda) account for 66% of deaths. This approach quantifies the measles burden by considering country-specific indicators, which can be updated, permitting an assessment of country, regional, and global changes in the burden associated with measles infection.

Time to right the wrongs: improving basic health care in Nigeria

Nigeria, once heralded as the beacon of Africa, has fallen somewhat short of this potential. Years of kleptocratic repressive dictators and military rule, coupled with widespread corruption, have resulted in large-scale neglect and deterioration of public services. Nowhere is this more apparent than within the health sector. Government-run health-care services barely function: half the population are unvaccinated for routine diseases, and a burgeoning epidemic of HIV/AIDS, only now being adequately addressed, leaves 3.5 million already infected and without access to the most basic of care. A poorly structured health service that relies on vertical programmes for HIV, tuberculosis, and malaria, means that coordination is chaotic, and already scant resources fail to reach the lower levels in which they are needed most. I visited Nigeria in October, 2001, with Médecins Sans Frontières, a humanitarian aid organisation that has been working in Nigeria since 1996. I witnessed the poor level of health care in Nigeria for myself--a country that is more than capable of providing effective services--and concluded that, even now, political priorities are being put ahead of the population's basic needs. The challenges to the new civilian government are monumental, and it is yet to show any solid commitment to improving the health of Africa's biggest nation.