Measles resurgence in southern Africa: challenges to measles elimination

Options in the Treatment of Subacute Sclerosing Panencephalitis: Implications for Low Resource Areas

Purpose of the review

Subacute sclerosing panencephalitis (SSPE) is a rare, slowly progressive, and frequently fatal neurodegenerative disorder caused by measles virus. The risk of SSPE remains significant globally, with fluctuating incidence noted in in tandem with measles vaccine uptake. This review aims to explore the current global status of SSPE, its treatment, and preventive measures.

Recent findings

An increase in measles cases have been reported in various parts of the world for different reasons related to the regional context of the outbreak. With reduction in measles vaccine doses since the onset of the COVID-19 pandemic, the future risk of SSPE can only accelerate. In recent years, subsequent cases of SSPE have been reported in the period following documented measles outbreaks in different settings. Concomitantly, there have been efforts to evaluate the efficacy of immunomodulatory, antiviral, and anti-seizure therapies that could ameliorate the devastating effects of this disease. This review elucidates on these approaches and their limitations, reasons for poor vaccine coverage in low- and middle-income countries, as well as the possible solutions to the prevention of measles and eventual avoidance of SSPE.

Summary

Prevention of measles virus infection with the resultant sequelae would be the most effective strategy for the management of SSPE. This approach would be particularly important in low resource setting that currently bears the double burden of widespread communicable diseases and malnutrition.

Vaccination strategies for measles control and elimination: time to strengthen local initiatives

BACKGROUND

Through a combination of strong routine immunization (RI), strategic supplemental immunization activities (SIA) and robust surveillance, numerous countries have been able to approach or achieve measles elimination. The fragility of these achievements has been shown, however, by the resurgence of measles since 2016. We describe trends in routine measles vaccine coverage at national and district level, SIA performance and demographic changes in the three regions with the highest measles burden.

FINDINGS

WHO-UNICEF estimates of immunization coverage show that global coverage of the first dose of measles vaccine has stabilized at 85% from 2015 to 19. In 2000, 17 countries in the WHO African and Eastern Mediterranean regions had measles vaccine coverage below 50%, and although all increased coverage by 2019, at a median of 60%, it remained far below levels needed for elimination. Geospatial estimates show many low coverage districts across Africa and much of the Eastern Mediterranean and southeast Asian regions. A large proportion of children unvaccinated for MCV live in conflict-affected areas with remote rural areas and some urban areas also at risk. Countries with low RI coverage use SIAs frequently, yet the ideal timing and target age range for SIAs vary within countries, and the impact of SIAs has often been mitigated by delays or disruptions. SIAs have not been sufficient to achieve or sustain measles elimination in the countries with weakest routine systems. Demographic changes also affect measles transmission, and their variation between and within countries should be incorporated into strategic planning.

CONCLUSIONS

Rebuilding services after the COVID-19 pandemic provides a need and an opportunity to increase community engagement in planning and monitoring services. A broader suite of interventions is needed beyond SIAs. Improved methods for tracking coverage at the individual and community level are needed together with enhanced surveillance. Decision-making needs to be decentralized to develop locally-driven, sustainable strategies for measles control and elimination.

Surprisingly Low Levels of Measles Immunity in Persons With HIV: A Seroprevalence Survey in a United States HIV Clinic

Background

Measles outbreaks have become increasingly common due to deteriorating vaccination rates, fluctuating herd immunity, and varying antibody decline. Limited knowledge exists regarding prevalence and risk factors associated with measles seronegativity among persons with HIV (PWH).

Methods

This was a cross-sectional study conducted at an academic HIV clinic in Omaha, Nebraska. Participants were screened for the presence of measles IgG antibody. Demographic and clinical information was obtained through electronic medical record review. Simple and multivariable logistic regressions were performed to identify risk factors for measles seronegativity.

Results

Three hundred fifty-one participants were enrolled, with a measles seroprevalence rate of 70.3%. The mean age (range) was 48 (20-74) years, 77% were male, and 53% were Caucasian. The mean CD4 nadir (range) was 334 (1-1675) cells/mm³. At the time of testing, 86% and 87% of the seronegative and seropositive participants had an HIV RNA <50 copies/mL, respectively. Younger age was significantly associated with measles seronegativity (P = .003), as was birth year after 1957 (P = .021). Prior history of measles infection was associated with seropositivity (P = .011). All other risk factors evaluated, including written documentation of adequate vaccination, were not associated with seronegativity.

Conclusions

Our study demonstrates a measles seroprevalence rate that is remarkably lower than previously reported in PWH (92%), and, more importantly, is considerably lower than the rate needed to maintain herd immunity (95%). With higher than expected seronegativity and absence of notable risk factors aside from age, our findings support expanded measles immunity screening for PWH who are at risk of measles exposure.

Recent setbacks in measles elimination: the importance of investing in innovations for immunizations

The recent setbacks in efforts to achieve measles elimination goals are alarming. To reverse the current trends, it is imperative that the global health community urgently intensify efforts and make resource commitments to implement evidence-based elimination strategies fully, including supporting research and innovations. The Immunization Agenda 2030: A Global Strategy to Leave No One Behind (IA2030) is the new global guidance document that builds on lessons learned and progress made toward the GVAP goals, includes research and innovation as a core strategic priority, and identifies measles as a “tracer” for improving immunisation services and strengthening primary health care systems. To achieve vaccination coverage and equity targets that leave no one behind, and accelerate progress toward disease eradication and elimination goals, sustained and predictable investments are needed for the identified research and innovations priorities for the new decade.

Measles outbreak in 2018-2019, Madagascar: epidemiology and public health implications

Introduction

In October 4^th, 2018, a measles outbreak was declared in Madagascar. This study describes the epidemiology of the outbreak and determines public health implications for measles elimination in Madagascar.

Methods

Data have been collected using line list developed for the outbreak. Serum samples were collected within 30 days of rash onset for laboratory testing; confirmation was made by detection of measles immunoglobulin M (IgM) antibody.

Results

A total of 2,930 samples were analysed in the laboratory among which 1,086 (37%) were laboratory confirmed. Measles cases age ranged from a minimum of 1 month to a maximum of 88 years. The median and the mean were 7 years and 9 years respectively. Children between 1 to 9 years accounted for 50.6% of measles cases. Attack rate (39,014 per 1,000,000 inhabitants) and case fatality rate (1.2%) were highest among children aged 9-11 months. A total of 67.2% cases were unvaccinated. As of March 14^th, 2019, all the 22 regions and 105 (92%) health districts out of 114 were affected by the measles outbreak in Madagascar.

Conclusion

Measles outbreak in Madagascar showed that the country is not on the track to achieve the goal of measles elimination by 2020.

Field challenges to measles elimination in the Democratic Republic of the Congo

BACKGROUND

During a measles epidemic, the Ministry of Public Health (MOH) of the Democratic Republic of the Congo conducted supplementary immunization activities (2016-SIA) from August 28-September 3, 2016 throughout Maniema Province. From October 29-November 4, 2016, Médecins Sans Frontières and the MOH conducted a reactive measles vaccination campaign (2016-RVC) targeting children six months to 14 years old in seven health areas with heavy ongoing transmission despite inclusion in the 2016-SIA, and a post-vaccination survey. We report the measles vaccine coverage (VC) and effectiveness (VE) of the 2016-SIA and VC of the 2016-RVC.

METHODS

A cross-sectional VC cluster survey stratified by semi-urban/rural health area and age was conducted. A retrospective cohort analysis of measles reported by the parent/guardian allowed calculation of the cumulative measles incidence according to vaccination status after the 2016-SIA for an estimation of crude and adjusted VE.

RESULTS

In November 2016, 1145 children (6-59 months old) in the semi-urban and 1158 in the rural areas were surveyed. Post-2016-SIA VC (documentation/declaration) was 81.6% (95%CI: 76.5-85.7) in the semi-urban and 91.0% (95%CI: 84.9-94.7) in the rural areas. The reported measles incidence in October among children less than 5 years old was 5.0% for 2016-SIA-vaccinated and 11.2% for 2016-SIA-non-vaccinated in the semi-urban area, and 0.7% for 2016-SIA-vaccinated and 4.0% for 2016-SIA-non-vaccinated in the rural area. Post-2016-SIA VE (adjusted for age, sex) was 53.9% (95%CI: 2.9-78.8) in the semi-urban and 78.7% (95%CI: 0-97.1) in the rural areas. Post 2016-RVC VC (documentation/declaration) was 99.1% (95%CI: 98.2-99.6) in the semi-urban and 98.8% (95%CI: 96.5-99.6) in the rural areas.

CONCLUSIONS

Although our VE estimates could be underestimated due to misclassification of measles status, the VC and VE point estimates of the 2016-SIA in the semi-urban area appear suboptimal, and in combination, could not limit the epidemic. Further research is needed on vaccination strategies adapted to urban contexts.

Subacute sclerosing panencephalitis: clinical phenotype, epidemiology, and preventive interventions

Subacute sclerosing panencephalitis (SSPE) is a preventable condition reported in 6.5 to 11 per 100 000 cases of measles, and highest in children who contracted measles infection when they were less than 5 years of age. Children residing in areas with poor vaccination coverage and high prevalence of human immunodeficiency virus are at increased risk of developing SSPE. SSPE is life-threatening in most affected children. This report documents current data relating to the clinical phenotype, epidemiology, and understanding of SSPE, inclusive of preventive interventions. While improvements in disease progression with immunomodulation may occur, overall there is no cure. Most therapies focus on supportive needs. Seizures and abnormal movements may respond to carbamazepine. Many countries advocate policies to enhance vaccination coverage. Effective preventive health care programmes, assurance of parental perceptions, and crisis support for unprecedented events obstructing effective primary health care are needed. Until measles is eradicated worldwide, children in all regions remain at risk. WHAT THIS PAPER ADDS: Measles contracted under 5 years of age has highest risk of developing subacute sclerosing panencephalitis (SSPE). Children with, or exposed to, human immunodeficiency virus infection, who contract measles may be at increased risk of SSPE.

Immunogenicity, effectiveness, and safety of measles vaccination in infants younger than 9 months: a systematic review and meta-analysis

BACKGROUND

Measles is an important cause of death in children, despite the availability of safe and cost-saving measles-containing vaccines (MCVs). The first MCV dose (MCV1) is recommended at 9 months of age in countries with ongoing measles transmission, and at 12 months in countries with low risk of measles. To assess whether bringing forward the age of MCV1 is beneficial, we did a systematic review and meta-analysis of the benefits and risks of MCV1 in infants younger than 9 months.

METHODS

For this systematic review and meta-analysis, we searched MEDLINE, EMBASE, Scopus, Proquest, Global Health, the WHO library database, and the WHO Institutional Repository for Information Sharing database, and consulted experts. We included randomised and quasi-randomised controlled trials, outbreak investigations, and cohort and case-control studies without restriction on publication dates, in which MCV1 was administered to infants younger than 9 months. We did the literature search on June 2, 2015, and updated it on Jan 14, 2019. We assessed: proportion of infants seroconverted, geometric mean antibody titre, avidity, cellular immunity, duration of immunity, vaccine efficacy, vaccine effectiveness, and safety. We used random-effects models to derive pooled estimates of the endpoints, where appropriate. We assessed methodological quality using the Grading of Recommendations, Assessment, Development, and Evaluation guidelines.

FINDINGS

Our search identified 1156 studies, of which 1071 were screened for eligibility. 351 were eligible for full-text screening, and data from 56 studies that met all inclusion criteria were used for analysis. The proportion of infants who seroconverted increased from 50% (95% CI 29-71) for those vaccinated with MCV1 at 4 months of age to 85% (69-97) for those were vaccinated at 8 months. The pooled geometric mean titre ratio for infants aged 4-8 months vaccinated with MCV1 compared with infants vaccinated with MCV1 at age 9 months or older was 0·46 (95% CI 0·33-0·66; I²=99·9%, p<0·0001). Only one study reported on avidity and suggested that there was lower avidity and a shorter duration of immunity following MCV1 administration at 6 months of age than at 9 months of age (p=0·0016) or 12 months of age (p<0·001). No effect of age at MCV1 administration on cellular immunity was found. One study reported that vaccine efficacy against laboratory-confirmed measles virus infection was 94% (95% CI 74-98) in infants vaccinated with MCV1 at 4·5 months of age. The pooled vaccine effectiveness of MCV1 in infants younger than 9 months against measles was 58% (95% CI 9-80; I²=84·9%, p<0·0001). The pooled vaccine effectiveness estimate from within-study comparisons of infants younger than 9 months vaccinated with MCV1 were 51% (95% CI -44 to 83; I²=92·3%, p<0·0001), and for those aged 9 months and older at vaccination it was 83% (76-88; I²=93·8%, p<0·0001). No differences in the risk of adverse events after MCV1 administration were found between infants younger than 9 months and those aged 9 months of older. Overall, the quality of evidence ranged from moderate to very low.

INTERPRETATION

MCV1 administered to infants younger than 9 months induces a good immune response, whereby the proportion of infants seroconverted increases with increased age at vaccination. A large proportion of infants receiving MCV1 before 9 months of age are protected and the vaccine is safe, although higher antibody titres and vaccine effectiveness are found when MCV1 is administered at older ages. Recommending MCV1 administration to infants younger than 9 months for those at high risk of measles is an important step towards reducing measles-related mortality and morbidity.

FUNDING

WHO.

Estimating the effect of measles vaccination on child growth using 191 DHS from 65 low- and middle-income countries

BACKGROUND

Childhood vaccinations reduce morbidity and mortality and are highly cost-effective. They may also protect children from malnutrition and lead to improved child growth. Stunting, wasting and underweight are targets used to monitor progress towards the achievement of the sustainable development goals (SDGs).

METHODS

We use data from Demographic and Health Surveys (DHS) covering the period from 1990 to 2017 to estimate the effect of measles vaccination at 12 months of age on stunting, wasting, and underweight. For causal estimation, we use household- and mother-fixed effects, which allows us to compare outcomes across siblings while controlling for all observed and unobserved confounders that are shared by the siblings, such as household social characteristics and home location. In addition, we control for a wide range of sibling-varying confounders, including sex, age, birth order and mother's age at birth, as well as vaccination with diphtheria-tetanus-polio (DPT), as a broad indicator of general likelihood to receive vaccinations.

RESULTS

Our samples include 347,808 individuals in 132 surveys from 59 countries (for stunting), 430,963 individuals in 190 surveys from 65 countries (for wasting), and 353,520 individuals in 130 surveys from 59 countries (for underweight). Measles vaccination is associated with significantly reduced odds of stunting (odds ratio 0.90 [95% CI 0.86-0.94], p < 0.001) and underweight (odds ratio 0.90 [95% CI 0.86-0.95], p < 0.001). The association with wasting is weaker and not statistically significant (odds ratio 0.95 [95% CI 0.89-1.02], p = 0.143). Our results remain robust across several alternative specifications of our regression models.

CONCLUSIONS

Measles vaccination substantially reduces stunting and underweight among children in low- and middle-income countries. Increasing measles coverage from the current low to near-universal levels would provide a large boost to child growth and the attainment of the SDGs.

Measles outbreak response decision-making under uncertainty: a retrospective analysis

Resurgent outbreaks of vaccine-preventable diseases that have previously been controlled or eliminated have been observed in many settings. Reactive vaccination campaigns may successfully control outbreaks but must necessarily be implemented in the face of considerable uncertainty. Real-time surveillance may provide critical information about at-risk population and optimal vaccination targets, but may itself be limited by the specificity of disease confirmation. We propose an integrated modelling approach that synthesizes historical demographic and vaccination data with real-time outbreak surveillance via a dynamic transmission model and an age-specific disease confirmation model. We apply this framework to data from the 1996-1997 measles outbreak in São Paulo, Brazil. To simulate the information available to decision-makers, we truncated the surveillance data to what would have been available at 1 or 2 months prior to the realized interventions. We use the model, fitted to real-time observations, to evaluate the likelihood that candidate age-targeted interventions could control the outbreak. Using only data available prior to the interventions, we estimate that a significant excess of susceptible adults would prevent child-targeted campaigns from controlling the outbreak and that failing to account for age-specific confirmation rates would underestimate the importance of adult-targeted vaccination.

Use of FTA Cards To Transport Throat Swabs and Oral Fluid Samples for Molecular Detection and Genotyping of Measles and Rubella Viruses

The genetic characterization of measles viruses is an important tool for measles surveillance. Reverse cold chain requirements for the transportation of samples to reference laboratories are challenging in resource-limited settings. FTA cards facilitate the transport of virologic samples at ambient temperature as noninfectious material; however, the utility of FTA cards for the detection and genotyping of measles virus from clinical samples has not been evaluated. Throat swabs (TS) and oral fluid (OF) samples were collected from suspected measles cases in the Democratic Republic of the Congo. Virus detection (reverse transcription-quantitative real-time PCR [RT-qPCR]) and genotyping (endpoint RT-PCR) were compared for samples from 238 suspected cases; these samples were either transported using the reverse cold chain or at ambient temperature on FTA cards. Virus detection showed excellent positive agreement for OF samples compared to TS (95.3%; confidence interval [CI], 91.6 to 97.4), in contrast to 79.4% (CI, 73.5 to 84.3) for TS on FTA, and 85.5% (CI, 80.2 to 89.6) for OF on FTA compared to OF samples. Genotyping results obtained for a subset of samples indicated that 77.3% of all TS and 71.0% of OF samples would produce genotype information compared to 41.6% of TS and 41.3% of OF on FTA cards. Similar results were found for 16 measles-negative samples that were confirmed as rubella cases. Measles genotype B3 and rubella genotype 2B were detected. FTA cards have limited utility for virologic surveillance of sporadic cases of measles; however, they can be a useful tool for the expansion of virologic surveillance in countries where the reverse cold chain is not available.

Understanding the causes and consequences of measles virus persistence

Measles is an acute systemic viral disease with initial amplification of infection in lymphoid tissue and subsequent spread over 10–14 days to multiple organs. Failure of the innate response to control initial measles virus (MeV) replication is associated with the ability of MeV to inhibit the induction of type I interferon and interferon-stimulated antiviral genes. Rather, the innate response is characterized by the expression of proteins regulated by nuclear factor kappa B and the inflammasome. With eventual development of the adaptive response, the rash appears with immune cell infiltration into sites of virus replication to initiate the clearance of infectious virus. However, MeV RNA is cleared much more slowly than recoverable infectious virus and remains present in lymphoid tissue for at least 6 months after infection. Persistence of viral RNA and protein suggests persistent low-level replication in lymphoid tissue that may facilitate maturation of the immune response, resulting in lifelong protection from reinfection, while persistence in other tissues (for example, the nervous system) may predispose to development of late disease such as subacute sclerosing panencephalitis. Further studies are needed to identify mechanisms of viral clearance and to understand the relationship between persistence and development of lifelong immunity.

How to Increase Vaccination Acceptance Among Apostolic Communities: Quantitative Results from an Assessment in Three Provinces in Zimbabwe

A worldwide increasing trend toward vaccine hesitancy has been reported. Measles outbreaks in southern Africa in 2009-2010 were linked to objections originating from Apostolic gatherings. Founded in Zimbabwe in the 1950s, the Apostolic church has built up a large number of followers with an estimated 3.5 million in Zimbabwe in 2014. To inform planning of interventions for the 2015 measles-rubella vaccination campaign, we assessed vaccination status and knowledge, attitudes and practices among purposive samples of Apostolic caregivers in three districts each in Harare City, Manicaland and Matabeleland South in Zimbabwe. We conducted structured interviews among 97 caregivers of children aged 9-59 months and collected vaccination status for 126 children. Main Apostolic affiliations were Johanne Marange (53%), Madida (13%) and Gospel of God (11%) with considerable variation across assessment areas. The assessment also showed considerable variation among Apostolic communities in children ever vaccinated (14-100%) and retention of immunization cards (0-83%) of ever vaccinated. Overall retention of immunization cards (12%) and documented vaccination status by card (fully vaccinated = 6%) were low compared to previously reported measures in the general population. Mothers living in monogamous relationships reported over 90% of all DTP-HepB-Hib-3, measles and up to date immunizations during the first life year documented by immunization card. Results revealed opportunities to educate about immunization during utilization of health services other than vaccinations, desire to receive information about vaccinations from health personnel, and willingness to accept vaccinations when offered outside of regular services. Based on the results of the assessment, specific targeted interventions were implemented during the vaccination campaign, including an increased number of advocacy activities by district authorities. Also, health workers offered ways and timing to vaccinate children that catered to the specific situation of Apostolic caregivers, including flexible service provision after hours and outside of health facilities, meeting locations chosen by caregivers, using mobile phones to set up meeting locations, and documentation of vaccination in health facilities if home-based records posed a risk for caregivers. Coverage survey results indicate that considerable progress has been made since 2010 to increase vaccination acceptability among Apostolic communities in Zimbabwe. Further efforts will be needed to vaccinate all Apostolic children during routine and campaign activities in the country, and the results from our assessment can contribute toward this goal.

Development of the World Health Organization Measles Programmatic Risk Assessment Tool Using Experience from the 2009 Measles Outbreak in Namibia

In the World Health Organization (WHO) African region, reported measles cases decreased by 80% and measles mortality declined by 88% during 2000-2012. Based on current performance trends, however, focused efforts will be needed to achieve the regional measles elimination goal. To prioritize efforts to strengthen implementation of elimination strategies, the Centers for Disease Control and Prevention and WHO developed a measles programmatic risk assessment tool to identify high-risk districts and guide and strengthen program activities at the subnational level. This article provides a description of pilot testing of the tool in Namibia using comparisons of high-risk districts identified using 2006-2008 data with reported measles cases and incidence during the 2009 outbreak. Of the 34 health districts in Namibia, 11 (32%) were classified as high risk or very high risk, including the district of Engela where the outbreak began in 2009. The district of Windhoek, including the capital city of Windhoek, had the highest overall risk score-driven primarily by poor population immunity and immunization program performance-and one of the highest incidences during the outbreak. Other high-risk districts were either around the capital district or in the northern part of the country near the border with Angola. Districts categorized as high or very high risk based on the 2006-2008 data generally experienced high measles incidence during the large outbreak in 2009, as did several medium- or low-risk districts. The tool can be used to guide measles elimination strategies and to identify programmatic areas that require strengthening.

Evidence of Mumps Infection Among Children in the Democratic Republic of Congo

BACKGROUND

Mumps is an acute viral infection and while the infection is usually mild, complications can lead to permanent sequelae including brain damage and deafness. The burden of mumps is currently unknown the Democratic Republic of Congo (DRC), we therefore assessed susceptibility to mumps infection among children 6-59 months of age.

METHODS

In collaboration with the 2013-2014 DRC Demographic and Health Survey, we conducted a serosurvey to assess population immunity to vaccine preventable diseases. Dried blood spot samples were collected from children 6 to 59 months of age and processed at the UCLA-DRC laboratory in Kinshasa, DRC using the Dynex Technologies Multiplier FLEX chemiluminescent immunoassay platform (Dynex multiplex assay, Chantilly, VA). Logistic multivariate analyses were used to determine risk factors for mumps seropositivity.

RESULTS

Serologic and survey data were matched for 7195, 6-59 month-old children, among whom 22% were positive and 3% indeterminate for mumps antibodies in weighted analyses. In multivariate analyses, the odds of seropositivity increased with increasing age, female gender, number of children in household, increasing socioeconomic status and province (Kinshasa with the highest odds of positive test result compared with all other provinces).

CONCLUSION

These data suggest that mumps virus is circulating in DRC and risk of exposure increases with age. At present, the introduction of a combined measles-mumps-rubella vaccine remains unlikely, as the capacity to maintain adequate vaccine coverage levels for routine immunization must be improved before additional antigens can be considered for the routine immunization schedule.

Demographic transition and the dynamics of measles in six provinces in China: A modeling study

BACKGROUND

Industrialization and demographic transition generate nonstationary dynamics in human populations that can affect the transmission and persistence of infectious diseases. Decades of increasing vaccination and development have led to dramatic declines in the global burden of measles, but the virus remains persistent in much of the world. Here we show that a combination of demographic transition, as a result of declining birth rates, and reduced measles prevalence, due to improved vaccination, has shifted the age distribution of susceptibility to measles throughout China.

METHODS AND FINDINGS

We fit a novel time-varying catalytic model to three decades of age-specific measles case reporting in six provinces in China to quantify the change in the age-specific force of infection for measles virus over time. We further quantified the impact of supplemental vaccination campaigns on the reduction of susceptible individuals. The force of infection of measles has declined dramatically (90%-97% reduction in transmission rate) in three industrialized eastern provinces during the last decade, driving a concomitant increase in both the relative proportion and absolute number of adult cases, while three central and western provinces exhibited dynamics consistent with endemic persistence (24%-73% reduction in transmission rate). The reduction in susceptible individuals due to supplemental vaccination campaigns is frequently below the nominal campaign coverage, likely because campaigns necessarily vaccinate those who may already be immune. The impact of these campaigns has significantly improved over time: campaigns prior to 2005 were estimated to have achieved less than 50% reductions in the proportion susceptible in the target age classes, but campaigns from 2005 onwards reduced the susceptible proportion by 32%-87%. A limitation of this study is that it relies on case surveillance, and thus inference may be biased by age-specific variation in measles reporting.

CONCLUSIONS

The age distribution of measles cases changes in response to both demographic and vaccination processes. Combining both processes in a novel catalytic model, we illustrate that age-specific incidence patterns reveal regional differences in the progress to measles elimination and the impact of vaccination controls in China. The shift in the age distribution of measles susceptibility in response to demographic and vaccination processes emphasizes the importance of progressive control strategies and measures to evaluate program success that anticipate and react to this transition in observed incidence.

Measles virus induces persistent infection by autoregulation of viral replication

Natural infection with measles virus (MV) establishes lifelong immunity. Persistent infection with MV is likely involved in this phenomenon, as non-replicating protein antigens never induce such long-term immunity. Although MV establishes stable persistent infection in vitro and possibly in vivo, the mechanism by which this occurs is largely unknown. Here, we demonstrate that MV changes the infection mode from lytic to non-lytic and evades the innate immune response to establish persistent infection without viral genome mutation. We found that, in the persistent phase, the viral RNA level declined with the termination of interferon production and cell death. Our analysis of viral protein dynamics shows that during the establishment of persistent infection, the nucleoprotein level was sustained while the phosphoprotein and large protein levels declined. The ectopic expression of nucleoprotein suppressed viral replication, indicating that viral replication is self-regulated by nucleoprotein accumulation during persistent infection. The persistently infected cells were able to produce interferon in response to poly I:C stimulation, suggesting that MV does not interfere with host interferon responses in persistent infection. Our results may provide mechanistic insight into the persistent infection of this cytopathic RNA virus that induces lifelong immunity.

The Immune Response in Measles: Virus Control, Clearance and Protective Immunity

Measles is an acute systemic viral infection with immune system interactions that play essential roles in multiple stages of infection and disease. Measles virus (MeV) infection does not induce type 1 interferons, but leads to production of cytokines and chemokines associated with nuclear factor kappa-light-chain-enhancer of activated B cells (NFκB) signaling and activation of the NACHT, LRR and PYD domains-containing protein (NLRP3) inflammasome. This restricted response allows extensive virus replication and spread during a clinically silent latent period of 10–14 days. The first appearance of the disease is a 2–3 day prodrome of fever, runny nose, cough, and conjunctivitis that is followed by a characteristic maculopapular rash that spreads from the face and trunk to the extremities. The rash is a manifestation of the MeV-specific type 1 CD4⁺ and CD8⁺ T cell adaptive immune response with lymphocyte infiltration into tissue sites of MeV replication and coincides with clearance of infectious virus. However, clearance of viral RNA from blood and tissues occurs over weeks to months after resolution of the rash and is associated with a period of immunosuppression. However, during viral RNA clearance, MeV-specific antibody also matures in type and avidity and T cell functions evolve from type 1 to type 2 and 17 responses that promote B cell development. Recovery is associated with sustained levels of neutralizing antibody and life-long protective immunity.

Age-specific mixing generates transient outbreak risk following critical-level vaccination

Measles elimination goals have been adopted in a range of countries, sub-regions, and regions since the WHO declared an elimination goal by 2015 or 2020. All countries attempt to achieve and maintain high coverage through routine immunization programmes. This routine strategy, however, does not ensure the elimination goal of measles. Many developed countries, such as the United States, that have succeeded in interrupting measles transmission earlier, are now experiencing outbreaks with an increasing number of cases. Using a stochastic, age-structured model of measles vaccination dynamics, we explore and characterize the transient dynamics of measles susceptibility in the years following the implementation of routine vaccination at the herd immunity threshold. We demonstrate how a population could face risks of potentially large outbreaks even within few years of vaccination. We characterize different risk profiles depending on the incidence pattern in the years prior to vaccination. These results suggest that the classic critical vaccination threshold is necessary to achieve herd immunity, but not sufficient to prevent long periods of transient, super-critical dynamics. Our results suggest the need of future work for more careful monitoring of the impacts of current immunization programmes, and developing models that take into account more complicated vaccination strategies, demographic factors, and population movements.

Measles seroprevalence, outbreaks, and vaccine coverage in Rwanda

BACKGROUND

Measles outbreaks are reported after insufficient vaccine coverage, especially in countries recovering from natural disaster or conflict. We compared seroprevalence to measles in blood donors in Rwanda and Sweden and explored distribution of active cases of measles and vaccine coverage in Rwanda.

METHODS

516 Rwandan and 215 Swedish blood donors were assayed for measles-specific immunoglobulin G (IgG) by enzyme-linked immunosorbent assay (ELISA). Data on vaccine coverage and acute cases in Rwanda from 1980 to 2014 were collected, and IgM on serum samples and polymerase chain reaction (PCR) on nasopharyngeal (NPH) swabs from suspected measles cases during 2010-2011 were analysed.

RESULTS

The seroprevalence of measles IgG was significantly higher in Swedish blood donors (92.6%; 95% CI: 89.1-96.1%) compared to Rwandan subjects (71.5%; 95% CI: 67.6-75.4%) and more pronounced <35 years of age. The OD values were significantly lower in the Rwandan blood donors as compared to Swedish subjects (p < 0.00001). However, effective measles vaccine coverage was concomitant with decrease in measles cases in Rwanda, with the exception of an outbreak in 1995 following the 1994 genocide. 76/544 serum samples were IgM positive and 21/31 NPH swabs were PCR positive for measles, determined by sequencing to be of genotype B3.

CONCLUSIONS

Measles seroprevalence was lower in Rwandan blood donors compared to Swedish subjects. Despite this, the number of reported measles cases in Rwanda rapidly decreased during the study period, concomitant with increased vaccine coverage. Taken together, the circulation of measles was limited in Rwanda and vaccine coverage was favourable, but seroprevalence and IgG levels were low especially in younger age groups.

Measles immunity among pregnant women aged 15-44 years in Namibia, 2008 and 2010

Background:

Namibia experienced a large measles outbreak starting in 2009, with 38% of reported cases in adults, including women of reproductive age. Population immunity was assessed among pregnant women to determine whether immunization activities were needed in adults to achieve measles elimination in Namibia.

Methods:

A total of 1708 and 2040 specimens sampled from Namibian pregnant women aged 15–44 years who were included in the 2008 and 2010 National HIV Sentinel Survey, respectively, were tested for measles immunoglobulin G antibody. The proportion of women seropositive overall and by 5-year age strata was determined, and factors associated with seropositivity were analyzed by logistic regression, including age, facility type, gravidity, HIV status, and urban/rural setting. Seropositivity in 2008 versus 2010 was compared.

Results:

In both analysis years, measles seropositivity was lower in 15–19-year-olds (77%) and 20–24-year-olds (85–87%) and higher in 25–44-year-olds (90–94%) (2008, p < 0.001; 2010, p < 0.001). Overall measles seropositivity did not differ between 2008 (87%) and 2010 (87%) (p = 0.7). HIV status did not affect seropositivity.

Conclusions:

Late in a large measles outbreak, 13% of pregnant women in Namibia, and almost one in four 15–19-year-old pregnant women, remained susceptible to measles. In Namibia, immunization campaigns with measles-containing vaccine should be considered for adults.

Vaccine receipt and vaccine card availability among children of the apostolic faith: analysis from the 2010-2011 Zimbabwe demographic and health survey

Introduction

Vaccine hesitancy and refusal continue to be a global challenge to reaching immunization targets, especially among those in traditional or fundamentalist religions. The apostolic faith in Zimbabwe has been historically associated with objection to most medical interventions, including immunization.

Methods

We conducted a descriptive analysis of socio-demographic characteristics and vaccine coverage among apostolic and non-apostolic adults aged 15-49 years and children aged 12-23 months using the Demographic and Health Survey conducted in Zimbabwe during 2010-2011. We used logistic regression models to estimate associations between the apostolic religion and receipt of all four basic childhood vaccinations in the Expanded Program on Immunization, receipt of no vaccinations, and availability of child vaccination card.

Results

Among children aged 12-23 months, 64% had received all doses of the four basic vaccinations, and 12% had received none of the recommended vaccines. A vaccination card was available for 68% of children. There was no significant association between Apostolic faith and completion of all basic vaccinations (aOR = 0.90, 95% CI: 0.69-1.17), but apostolic children were almost twice as likely to have received no basic vaccinations (aOR = 1.83, 95% CI: 1.22-2.77) than non-Apostolic children, and they were 32% less likely to have a vaccination card that was available and seen by the interviewer (aOR = 0.68, 95% CI: 0.52-0.89).

Conclusion

Disparities in childhood vaccination coverage and availability of vaccination cards persist for apostolic in Zimbabwe. Continued collaboration with apostolic leaders and additional research to better understand vaccine hesitancy and refine interventions and messaging strategies are needed.

The 2013 measles outbreak in Sri Lanka: experience from a rural district and implications for measles elimination goals

BACKGROUND

Sri Lanka was the first country in the Southeast Asian region to achieve its measles elimination goal in 2011. In 2012, the measles immunization schedule changed from a measles vaccine at 9 months to a measles, mumps and rubella vaccine at 12 months. However in 2013, Sri Lanka reported its worst recent outbreak of measles. This study investigated a part of this outbreak in order to describe its epidemiology.

METHODS

A prospective study was carried out at the university medical unit of the Teaching Hospital, Anuradhapura (THA), the third largest hospital in Sri Lanka, from October 2013 until March 2014. An epidemiological profile of patients was constructed, case confirmation was done on all suspected cases and the basic demographic details of these suspected cases were obtained from the available records.

RESULTS

From January 2013 to March 2014, 101 measles suspects were admitted to the THA. Until June 2013, all suspected cases were aged below 12 months of age. During the study period (15 months), the total number of patients aged below 9 months, 9 to 12 months, 1 to 11 years, 12-29 years and over 29 years were 10 (9.9 %), 11 (10.9 %), 6 (5.9 %), 37 (36.6 %) and 36 (35.6 %), respectively (data missing-1). Out of the 33 patients clinically suspected, 32 tested positive for measles. Common clinical features included: fever (n = 33, 100 %), maculopapular rash (n = 33), conjunctivitis (n = 31), posterior cervical lymphadenopathy (n = 23) and Koplik's spots (n = 8). Features suggestive of pneumonia were observed among 30 (90.9 %) patients and 26 (78.8 %) had diarrhoea. Two patients (6.1 %) who developed severe pneumonia received care at an intensive care unit due to respiratory difficulties. Out of 33 patients, 15 (45.5 %) had prior immunization for measles, two (6.1 %) reported that they never had a measles immunization and 16 (48.5 %) were unsure about their immunization status. Out of those who reported they were previously immunized, 11 (73.3 %) belonged to the age group of 12-2 years.

CONCLUSION

Because the first cases of this outbreak were infants, an increase in susceptible infants due to the change in the vaccine schedule could partly explain the outbreak.

The effect of immunization on measles incidence in the Democratic Republic of Congo: Results from a model of surveillance data

BACKGROUND

Measles continues to be a leading cause of vaccine-preventable disease mortality among children under five despite a safe and efficacious vaccine being readily available. While global vaccination coverage has improved tremendously, measles outbreaks persist throughout sub-Saharan Africa. Since 2010, the Democratic Republic of Congo (DRC) has seen a resurgence of measles outbreaks affecting all 11 provinces. These outbreaks are mainly attributed to gaps in routine immunization (RI) coverage compounded with missed supplementary immunization activities (SIAs). We utilized national passive surveillance data from DRC's Integrated Disease Surveillance and Response (IDSR) system to estimate the effect of immunization on measles incidence in DRC.

METHODS

We investigated the decline in measles incidence post-immunization with one dose of measles containing vaccine (MCV1) with and without the addition of supplementary immunization activities (SIAs) and outbreak response immunization (ORI) campaigns. Measles case counts by health zone were obtained from the IDSR system between January 1, 2010 and December 31, 2013. The impact of measles immunization was modeled using a random effects multi-level model for count data with RI coverage levels and mass campaign activities from one year prior.

RESULTS

The presence of an SIA (aIRR [95% CI] 0.86 [0.60-1.25]) and ORI (0.28 [0.20-0.39]) in the year prior were both associated with a decrease in measles incidence. When interaction terms were included, our results suggested that the high levels of MCV1 reported in the year prior and the presence of either mass campaign was associated with a decrease in measles incidence.

CONCLUSIONS

Our results highlight the importance of a two-dose measles vaccine schedule and the need for a strong routine immunization program coupled with frequent SIAs. Repeated occurrences of large-scale outbreaks in DRC suggest that vaccination coverage rates are grossly overestimated and signify the importance of the evaluation and modification of measles prevention and control strategies.

[Exanthems and fever in travellers returning from the tropics]

Dengue fever with its subtle rash is today more common than malaria in travellers returning to Europe from the tropics (meta-analysis Geo Sentinel network). Up to 5 % of all safari tourists experience African tick bite fever during or soon after their journey; it is caused by rickettsiae and clinically presents with exanthems, focal necrotizing vasculitis (eschar, tache noir), lymphadenopathy and moderate fever. Typhoid fever is a severe infectious disease is which is difficult to diagnosis at first assessment. The presence of rose spots, which may be found in up to 33 % of patients with typhoid fever, can lead the way to diagnosis. Exanthems can be subtle and may occur weeks after infection without any other distinctive clinical sign. Particular importance in travel medicine has to be paid to acute HIV infection and secondary syphilis after exposition and infection in the tropics. Also the highly contagious infectious diseases of childhood as measles and rubeola have to be taken into account in adults with no or insufficient vaccination after a stay in tropical countries.

Antecedent causes of a measles resurgence in the Democratic Republic of the Congo

INTRODUCTION

Despite accelerated measles control efforts, a massive measles resurgence occurred in the Democratic Republic of the Congo (DRC) starting in mid-2010, prompting an investigation into likely causes.

METHODS

We conducted a descriptive epidemiological analysis using measles immunization and surveillance data to understand the causes of the measles resurgence and to develop recommendations for elimination efforts in DRC.

RESULTS

During 2004-2012, performance indicator targets for case-based surveillance and routine measles vaccination were not met. Estimated coverage with the routine first dose of measles-containing vaccine (MCV1) increased from 57% to 73%. Phased supplementary immunization activities (SIAs) were conducted starting in 2002, in some cases with sub-optimal coverage (≤95%). In 2010, SIAs in five of 11 provinces were not implemented as planned, resulting in a prolonged interval between SIAs, and a missed birth cohort in one province. During July 1, 2010-December 30, 2012, high measles attack rates (>100 cases per 100,000 population) occurred in provinces that had estimated MCV1 coverage lower than the national estimate and did not implement planned 2010 SIAs. The majority of confirmed case-patients were aged <10 years (87%) and unvaccinated or with unknown vaccination status (75%). Surveillance detected two genotype B3 and one genotype B2 measles virus strains that were previously identified in the region.

CONCLUSION

The resurgence was likely caused by an accumulation of unvaccinated, measles-susceptible children due to low MCV1 coverage and suboptimal SIA implementation. To achieve the regional goal of measles elimination by 2020, efforts are needed in DRC to improve case-based surveillance and increase two-dose measles vaccination coverage through routine services and SIAs.

Trends of rubella incidence during a 5-year period of case based surveillance in Zimbabwe

BACKGROUND

Rubella is a disease of public health significance owing to its adverse effects during pregnancy and on pregnancy outcomes. Women who contract rubella virus during pregnancy may experience complications such as foetal death or give birth to babies born with congenital rubella syndrome. Vaccination against rubella is the most effective and economical approach to control the disease, and to avoid the long term effects and high costs of care for children with congenital rubella syndrome as well as to prevent death from complications. Zimbabwe commenced rubella surveillance in 1999, despite lacking a rubella vaccine in the national Expanded Programme on Immunization, as per the World Health Organization recommendation to establish a surveillance system to estimate the disease burden before introduction of a rubella vaccine. The purpose of this analysis is to describe the disease trends and population demographics of rubella cases that were identified through the Zimbabwe national measles and rubella case-based surveillance system during a 5-year period between 2007 and 2011.

METHODS

Data from the Zimbabwe National Measles Laboratory for the 5-year study period were analysed for age, sex, district of origin, seasonality, and rubella IgM serostatus.

RESULTS

A total of 3428 serum samples from cases of suspected measles in all administrative districts of the country were received by the laboratory during this period. Cases included 51% males and 49% females. Of these, 2999 were tested for measles IgM of which 697 (23.2%) were positive. Of the 2302 measles IgM-negative samples, 865 (37.6%) were rubella IgM-positive. Ninety-eight percent of confirmed rubella cases were children younger than 15 years of age. Most infections occurred during the dry season.

CONCLUSIONS

The national case-based surveillance revealed the disease burden and trends of rubella in Zimbabwe. These data add to the evidence for introducing rubella-containing vaccine into the national immunization programme.

Measles in Morocco: epidemiological profile and impact of vaccination strategy

INTRODUCTION

Measles continues to persist as one of the leading causes of infant mortality due to preventable diseases through vaccination. This study aims to highlight measles in Morocco, and to present the vaccination strategy implemented to control and eliminate the disease in this country.

METHODS

Throughout this study, and based on data from the Directorate of Epidemiology and Control of Diseases and those of the Directorate of Population, we present an overview on the epidemiological trends of measles from 1997 to 2012, while evoking the plans established by the Ministry of Health (MoH) for the control and elimination of this disease.

RESULTS

The number of measles cases has decreased in Morocco between 1997 and 2012 (2574-720 reported cases per year) as a result of four important steps: first, increasing the routine vaccination coverage (73-94%); second, the introduction of the second dose of the combined vaccine against measles and rubella in schools (children aged 6 years) since 2003; third, the first catch-up campaign of vaccination in Morocco in 2008, for which coverage was highly satisfactory (96% and 100% for age groups 5-59 months and 5-14 years, respectively); and fourth, the organization of a mass vaccination campaign in 2013 that targeted children from aged 9 months to 19 years.

CONCLUSION

The vaccination plan and the surveillance system executed in Morocco within the framework of the regional project implemented by the World Health Organization (WHO) to eliminate measles has given remarkable results regarding the reduction of measles cases and mortality due to this disease. According to the data from MoH and WHO, the number of reported and confirmed measles cases decreased drastically during 2014. However, these efforts are still unsatisfactory compared to the prospective of eliminating the disease by 2015.

The effects of maternal immunity and age structure on population immunity to measles

Measles was successfully eradicated in the Pan-American Health Region in 2002. However, maintenance of elimination in parts of Africa, Europe, the USA, and other regions is proving difficult, despite apparently high vaccine coverage. This may be due to the different age structure in developed and developing populations, as well as to differences in the duration of maternal immunity. We explore the interaction between maternal immunity and age structure and quantify the resulting immunity gap between vaccine coverage and population immunity; we use this immunity gap as a novel metric of vaccine program success as it highlights the difference between actual and estimated immunity. We find that, for some combinations of maternal immunity and age structure, the accepted herd immunity threshold is not maintainable with a single-dose vaccine strategy for any combination of target age and coverage. In all cases, the herd immunity threshold is more difficult to maintain in a population with developing age structure. True population immunity is always improved if the target age at vaccination is chosen for the specific combination of maternal immunity and age structure.

Vaccine hesitancy, vaccine refusal and the anti-vaccine movement: influence, impact and implications

Despite being recognized as one of the most successful public health measures, vaccination is perceived as unsafe and unnecessary by a growing number of parents. Anti-vaccination movements have been implicated in lowered vaccine acceptance rates and in the increase in vaccine-preventable disease outbreaks and epidemics. In this review, we will look at determinants of parental decision-making about vaccination and provide an overview of the history of anti-vaccination movements and its clinical impact.