Towards elimination: measles susceptibility in Australia and 17 European countries

OBJECTIVE: To evaluate age-specific measles susceptibility in Australia and 17 European countries. METHODS: As part of the European Sero-Epidemiology Network 2 (ESEN2), 18 countries collected large national serum banks between 1996 and 2004. These banks were tested for measles IgG and the results converted to a common unitage to enable valid intercountry comparisons. Historical vaccination and disease incidence data were also collected. Age-stratified population susceptibility levels were compared to WHO European Region targets for measles elimination of < 15% in those aged 2-4 years, < 10% in 5-9-year-olds and < 5% in older age groups. FINDINGS: Seven countries (Czech Republic, Hungary, Luxembourg, Spain, Slovakia, Slovenia and Sweden) met or came very close to the elimination targets. Four countries (Australia, Israel, Lithuania and Malta) had susceptibility levels above WHO targets in some older age groups indicating possible gaps in protection. Seven countries (Belgium, Bulgaria, Cyprus, England and Wales, Ireland, Latvia and Romania) were deemed to be at risk of epidemics as a result of high susceptibility in children and also, in some cases, adults. CONCLUSION: Although all countries now implement a two-dose measles vaccination schedule, if the WHO European Region target of measles elimination by 2010 is to be achieved higher routine coverage as well as vaccination campaigns in some older age cohorts are needed in some countries. Without these improvements, continued measles transmission and outbreaks are expected in Europe.     

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.     

Cost-benefit analyses of supplementary measles immunisation in the highly immunized population of New Zealand

As endemic measles is eliminated from countries through increased immunisation, the economic benefits of enhanced immunisation programs may come into question. New Zealand has suffered from outbreaks after measles introductions from abroad and we use it as a model system to understand the benefits of catch up immunisation in highly immunised populations. We provide cost-benefit analyses for measles supplementary immunisation in New Zealand. We model outbreaks based on estimates of the basic reproduction number in the vaccinated population (R_v, the number of secondary infections in a partially immunised population), based on the number of immunologically-naïve people at district and national levels, considering both pre- and post-catch up vaccination scenarios. Our analyses suggest that measles R_v often includes or exceeds one (0.18–3.92) despite high levels of population immunity. We calculate the cost of the first 187 confirmed and probable measles cases in 2014 to be over NZ$1 million (∼US$864,200) due to earnings lost, case management and hospitalization costs. The benefit-cost ratio analyses suggest additional vaccination beyond routine childhood immunisation is economically efficient. Supplemental vaccination-related costs are required to exceed approximately US$66 to US$1877 per person, depending on different scenarios, before supplemental vaccination is economically inefficient. Thus, our analysis suggests additional immunisation beyond childhood programs to target naïve individuals is economically beneficial even when childhood immunisation rates are high.     

Models of strategies for control of rubella and congenital rubella syndrome—A 40 year experience from Australia

We investigated the impact of vaccination on rubella epidemiology in Australia, using a mathematical model fitted to Australian serosurvey data and incorporating pre-vaccination European estimates of rubella transmissibility. Mass infant measles–mumps–rubella (MMR) vaccination produced a 99% reduction in both rubella and congenital rubella syndrome (CRS) incidence by 2010 compared to the pre-vaccination era (1960–70). The model is consistent with reductions in CRS based on surveillance of congenital hearing impairment. Model simulations suggest that selective schoolgirl vaccination (1971–88) was associated with a 90% reduction in CRS incidence, but only a 1–4% reduction in rubella incidence. Our model predicted that these reductions in rubella were much less vulnerable to reductions in MMR vaccine coverage than for measles. In the future, a less than 15% decrease in MMR vaccine coverage is estimated to have minimal impact before 2060, but a 20% reduction may result in a 7-fold increase in rubella incidence, with the effective reproductive number R rising from 0.28 to 0.78 by 2060. The 99% reduction in both rubella and CRS incidence and low effective reproductive number (R ≤ 0.28) we documented after 2010 are consistent with Australia having achieved rubella elimination.     

Predicting localised measles outbreak potential in Australia

IntroductionAustralia has achieved measles elimination as announced in March 2014 by the WHO Western Pacific Regional Committee, based on several lines of evidence. However, despite strong national evidence for elimination, there remains substantial regional variation in vaccine coverage, has resulted in recent outbreaks and potential for increased frequency in the future.MethodsIn this study, we apply a multiple cohort model of measles immunity, stratified by age and local geographic area to predict trends in the measles reproduction number R. In addition, we use branching process models of outbreak risks to predict state-level probabilities of the occurrence of measles outbreaks over the next 20 years.ResultsOur results suggest increasing risks of large measles outbreaks over this period, in particular in the states of Queensland and New South Wales. In addition, there is wide variation in predicted R values by smaller geographic areas, although uncertainty in age-specific immunity limits the precision of our results.DiscussionOur predictions align with observed outbreaks in Australian states and suggest our approach to determining future outbreak risks could be applied more widely in elimination or near-elimination settings.     

Sero-epidemiology of measles-specific IgG antibodies and predictive factors for low or missing titres in a German population-based cross-sectional study in children and adolescents (KiGGS)

Background and objective

In the European Region, measles elimination is now targeted to 2015. To measure progress towards elimination age-group specific susceptibility targets have been defined. Age-specific measles susceptibility in children and adolescents was evaluated in Germany. Taking into account a broad range of socio-demographic, health- and vaccination status related variables, populations for vaccination campaigns were identified.

Method

We analysed data from children aged 1-17 years in the representative German Health Interview and Examination Survey for Children and Adolescents (KiGGS). Measles immunoglobulin G antibodies were measured in 13,977 participants by enzyme immunoassay (ELISA). Bivariate and multivariate logistic regression analyses were used to determine parental and infant related factors associated with measles susceptibility.

Results

The overall prevalence of seronegativity in children tested for measles IgG aged 1-17 years was 10.0% (95% CI 9.4-10.7). The prevalence of seronegativity in the German population was below the WHO targets for measles elimination in children aged 2-9 year-olds but exceeded the target for 10-17 year-olds. Age differences in the level of seronegativity were found to be mainly due to differences in vaccination coverage. A higher level of susceptibility was observed if parents did not comply with the request to present the child's vaccination card. In vaccinated children, immigration, male gender, very young age at first vaccination and a longer time period since last vaccination were associated with a higher level of susceptibility.

Conclusion

Further increase of the two-dose vaccination coverage is necessary in order to achieve the WHO targets. Catch up vaccination campaigns should focus on adolescents and immigrants.     

Evaluating the population measles susceptibility in Tianjin,China

BackgroundMeasles is a highly infectious illness requiring herd immunity of 95% to interrupt transmission. China has not reached elimination goals despite high vaccination coverage. We estimated the population susceptibility against measles in Tianjin, China and to tailor awareness raising activities in the measles elimination plan.MethodsAge-specific measles seroprevalence was evaluated by Enzyme-Linked Immunosorbent Assay (ELISA) on 12,164 individual aged 0–44 years in 2009–2018. Measles IgG avidity testing was performed to confirm the relationship of the waning immunity after vaccination and secondary vaccination failures (SVF) on 324 confirmed measles cases in 2013–2018.Results11,108 samples (91.32%) tested positive for measles IgG, 239 (1.96%) tested as equivocal and 817 (6.72%) were negative. The age distribution of measles cases in Tianjin followed a U-shaped curve and was highest for those at <8 months and again at 20–39 years which correlated closely with the age distribution of measles susceptibility based on measles IgG antibody status (r = 0.72, P < 0.001). The seropositivity rate and antibody geometric mean concentration (GMC) for the 2018 study population were significantly lower (χ² = 7.45, P = 0.006 and t = 12.01, P < 0.001) compared to 2009. The multivariate stepwise logistic regression analysis showed that age and region were the risk factors for both measles seropositivity rate and GMC after vaccination. The proportion of high avidity cases increased with age, being significantly higher in 75.31% of cases in patients aged 30–34 years (χ² = 18.04, P = 0.003).ConclusionsHigh immunization coverage in children alone will not be adequate to realizing sufficient levels of population herd immunity, particularly given that the potential susceptibility window in adult. Implementation of supplemental immunization activity (SIA) targeted to appropriate group aged 30–34 years is recommended.     

Measles epidemiology and vaccination coverage in Oromia Region,Ethiopia: Evidence from surveillance, 2011–2018

Despite a reported high coverage of measles-containing vaccine (MCV), low-income countries including, Ethiopia, have sustained high measles transmission with frequent outbreaks. We investigated the distribution of measles infection and vaccination in Oromia Regional State, Ethiopia. According to the World Health Organization (WHO) and the Ethiopian measles case classification guidelines, measles cases were classified as laboratory-confirmed, clinically compatible, and epidemiologically linked. We derived measles vaccination coverage estimates using reported measles vaccine efficacy and, the proportion of measles cases vaccinated with measles vaccine at least once from the surveillance data. We calculated measles effective reproduction number (R_e) in the region. Almost twenty-five thousand measles cases were reported through the surveillance system, with more than 50% of the suspected and confirmed measles cases reported in 2015. Measles had sustained and high transmission rate with uneven distribution among the zones. Children between 1 and 4 years of age and MCV unvaccinated individuals were the most affected groups. In all the zones, the average surveillance-estimated MCV coverage among both infants and under-five children was significantly lower than the WHO recommended minimum 90% threshold herd-immunity. With this level of vaccination coverage, an infected case can transmit to more than four individuals. Nevertheless, the administrative coverage reports for the concurrent period were consistently above 90%. The estimated MCV coverage across the Oromia region was well below the recommended herd-immunity threshold. It partly explains the apparent mismatch of sustained measles transmission and outbreaks despite the very high administrative coverage estimates. Oromia regional health bureau, in collaboration with key stakeholders, should make a concerted effort to increase the effective-coverage of MCV to at least 90%. Additionally, multiple-dose MCV has to be scaled-up and accompanied with appropriate geographic and age targeting using evidence from surveillance data. Immediate programmatic action is needed to improve the quality of measles surveillance.     

Increasing seroprevalence but waning herd immunity against measles after elimination: Longitudinal seroepidemiology of measles in Osaka Prefecture,Japan, 2003–2020

Japan is one of the countries conducting longitudinal serosurveillance of vaccine-preventable diseases. We conducted surveillance of the local measles-specific antibody titer, calculated the effective reproduction number (R_e), and compared data of four terms: term 1, 2003–2006 (before the introduction of the second shot of measles-containing vaccine); term 2, 2007–2010 (early term toward measles elimination); term 3, 2011–2014 (later term toward measles elimination); and term 4, 2015–2020 (after elimination of measles in Japan). Approximately 250 sera from volunteers aged 0 to ≥ 40 years were collected and examined for measles-specific IgG using the gelatin particle agglutination (PA) method annually from 2003 to 2020. Seroprevalence and the geometric mean of the PA antibody titer were examined by term. R_e was calculated using the age-dependent proportion immune and contact matrix for each term. Of the 4,716 sera, 886 in term 1, 1,217 in term 2, 1,069 in term 3, and 1,544 in term 4 were collected. The seroprevalence gradually increased from term 1 (88.3% CI 86.0–90.3) to term 4 (95.7% CI 94.6–96.7), and the seroprevalence of term 1 was significantly lower than those of other terms (Fisher’s exact test, p < 0.001), with PA titer ≥ 16 as positive. By contrast, PA antibody titers significantly decreased from term 1 (median 1,024) to term 4 (median 256) (Mann–Whitney U test, p < 0.001). With the protection level (PA titer ≥ 128 and ≥ 256) as positive, R_e gradually increased from term 1 (1.8 and 2.3) to term 4 (2.5 and 4.8, respectively). Waning levels of measles antibodies potentially increase the measles susceptibility in Osaka, Japan. This trend might imply a limitation of vaccine-induced immunity in the absence of a natural booster for wild strains after measles elimination. This study provides a cue for maintaining continuous measles elimination status in the future.     

Parental attitudes and decision-making regarding MMR vaccination in an anthroposophic community in Sweden – A qualitative study

Measles outbreaks occur regularly throughout Europe, up to 31 500 cases in the previous year, particularly where there are pockets of populations with lower vaccination coverage than the recommended ≥95%. Anthroposophic communities in Europe are one of several groups with relatively low vaccination coverage. In Sweden, outbreaks of measles and rubella were reported from an anthroposophic community. Thus the aim of this qualitative study was to explore facilitators and barriers to MMR vaccination among parents living in anthroposophic communities in Sweden. Twenty parents living in an anthroposophic community were interviewed, focusing on their views and decisions on MMR vaccination. The interviews were analyzed using qualitative content analysis. Two overarching views of health emerged, differentiating broadly parents who vaccinate vs. parents who do not vaccinate. Four themes describing parental attitudes toward measles vaccination were developed and three of these, the conformers, the pragmatists and the attentive delayers describe different approaches toward vaccinations among those who actually vaccinate. The last theme, promoters of natural immunity, represents those postponing or refusing vaccination beyond childhood. This study suggests that there is a spectrum of parental beliefs regarding MMR vaccination in this anthroposophic community. Interventions specifically targeted to the anthroposophic community and strengthening health workers capacity for a constructive dialog on vaccine's benefit and risks may contribute to higher vaccination coverage. This is believed to minimize the risk of future epidemics and contribute to the WHO European Region's goal of eliminating measles.     

Progress towards measles elimination in Singapore

ObjectiveWe describe the epidemiological trends of measles in Singapore in relation to its progress towards measles elimination and identify gaps in fulfilling the World Health Organization Western Pacific Regional Office regional measles elimination criteria.MethodsEpidemiological data on measles maintained by the Communicable Diseases Division, Ministry of Health from 1981 to 2012 were collated and analysed. Data on measles vaccination coverage were obtained from the National Immunization Registry and School Health Services, Health Promotion Board. To assess the seroprevalence of the population, the findings of periodic seroepidemiological surveys on measles were traced and reviewed.FindingsWith the successful implementation of the National Childhood Immunization Programme using the monovalent measles vaccine, measles incidence declined from 88.5 cases per 100,000 in 1984 to 6.9 per 100,000 in 1991. Resurgences were observed in 1992, 1993 and 1997. A ‘catch-up’ vaccination programme using the trivalent measles, mumps and rubella (MMR) vaccine was conducted in 1997, followed by introduction of the two-dose vaccination schedule in January 1998. Measles incidence subsequently declined sharply to 2.9 per 100,000 in 1998. Vaccination coverage was maintained at 95% for the first dose and 92–94% for the second dose. Seroprevalence surveys showed seropositivity for measles IgG antibodies in over 95% of adults in 2004, and in 83.1% of children aged 1–17 years in 2008–2010. Sporadic cases with occasional clusters of two or more cases continued to occur among the unvaccinated population, especially children aged below 4 years. The predominant measles virus genotype has shifted from D9 to the B3 and G3 genotypes, which are endemic in neighbouring countries.ConclusionSingapore has made good progress towards the elimination of endemic measles. To further eliminate sporadic cases of measles, the national immunisation schedule has recently been amended to vaccinate children with 2 doses of MMR vaccine before 2 years of age.     

The potential for measles transmission in England

Background  

Since the schools vaccination campaign in 1994, measles has been eliminated from England. Maintaining elimination requires low susceptibility levels to keep the effective reproduction number R below 1. Since 1995, however, MMR coverage in two year old children has decreased by more than 10%.     

Accuracy of routine data on MMR vaccination coverage and validity of parental recall of vaccination

A study was conducted to re-validate the measles, mumps and rubella (MMR) coverage and measles susceptibility in children resident in Bolton and born between 1991 and 1995; also to examine the accuracy of parental recall of children's MMR vaccination status. Using general practitioner/practice held records, a validation survey was conducted on a random sample of 171 reportedly unvaccinated children. A questionnaire survey was used to assess parental recall. 'Records' to 'recall' agreement was examined. One- and two-dose population coverage according to routine data was 94.6% and 75.2% respectively, with measles susceptibility of 8.1%. Based on the 'records' survey, one- and two-dose population coverage estimates were 97.4% (+2.8%) and 78.9% (+3.7%), with a revised susceptibility estimate of 5.2%, respresenting a 36% reduction in the susceptibility fraction. Routine data may modestly underestimate vaccination coverage and significantly overestimate measles susceptibility. Many parents of MMR unvaccinated children believe that their children have been vaccinated.     

Comparative Distributional Impact of Routine Immunization and Supplementary Immunization Activities in Delivery of Measles Vaccine in Low- and Middle-Income Countries

ObjectivesIn many countries, measles disproportionately affects poorer households. To achieve equitable delivery, national immunization programs can use 2 main delivery platforms: routine immunization and supplementary immunization activities (SIAs). The objective of this article is to use data concerning measles vaccination coverage delivered via routine and SIA strategies to make inferences about the associated equity impact.MethodsWe relied on Demographic and Health Survey and Multiple Indicator Cluster Surveys multi-country survey data to conduct a comparative analysis of routine and SIA measles vaccination status of children by wealth quintile. We estimated the value of the angle, θ, for the ratio of the difference between coverage levels of adjacent wealth quintiles by using the arc-tangent formula. For each country/year observation, we averaged the θ estimates into one summary measurement, defined as the “equity impact number.”ResultsAcross 20 countries, the equity impact number summarized across wealth quintiles was greater (and hence less equitable) for routine delivery than for SIAs in the survey rounds (years) during, before, and after an SIA about 65% of the time. The equity impact numbers for routine measles vaccination averaged across wealth quintiles were usually greater than for SIA measles vaccination across country-year observations.ConclusionsThis analysis examined how different measles vaccine delivery platforms can affect equity. It can serve to elucidate the impact of immunization and public health programs in terms of comparing horizontal to vertical delivery efforts and in reducing health inequalities in global and country-level decision-making.     

Global measles control and regional elimination, 1998-1999

In 1989, the World Health Assembly adopted the goal of reducing measles morbidity and mortality by 90% and 95%, respectively, by 1995, compared with estimates of the disease burden in the prevaccine era. In 1990, the World Summit for Children adopted a goal of vaccinating 90% of children against measles by 2000. Three regions of the World Health Organization (WHO) have targeted elimination: in 1994, the American Region (AMR) targeted elimination by 2000; in 1997, the Eastern Mediterranean Region (EMR) targeted elimination by 2010; and in 1998, the European Region (EUR) targeted elimination by 2007. This report updates progress since 1997 toward global measles control and regional elimination of measles, and includes vaccination coverage and disease surveillance data received by WHO as of August 14, 1999. Data for 1998 suggest that routine measles vaccination coverage has declined in some regions, the number of countries reporting cases and coverage to WHO has decreased, and measles continues to be an important cause of morbidity and mortality.     

Estimating vaccination coverage for routinely recommended vaccines among children aged 24 months and adolescents aged 13 through 17 years using data from immunization information systems in the United States

ObjectiveTo use a model-based approach to estimate vaccination coverage of routinely recommended childhood and adolescent vaccines for the United States.MethodsWe used a hierarchical model with retrospective cohort data from eleven IIS jurisdictions, which contains vaccination records submitted by providers. Numerators included data from 2014 to 2019 at the county level for 2.4 million children at age 24 months and 14.4 million adolescents aged 13–17. Age-appropriate Census populations were used as denominators. Covariates associated with childhood and adolescent vaccinations were included in the model. Model-based estimates for each county were generated and aggregated to the national level to produce national vaccination coverage estimates and compared to National Immunization Survey (NIS) estimates of vaccination coverage. Trends of estimated vaccination coverage were compared between the model-based approach and NIS.ResultsFrom 2014 to 18, model-based national vaccination coverage estimates were within ten percentage points of NIS-Child vaccination coverage estimates for most vaccines among children at age 24 months. One notable difference was higher model-based vaccination coverage estimates for hepatitis B birth dose compared to NIS-Child coverage estimates. From 2014 to 19, model-based national vaccination coverage estimates were within ten percentage points of NIS-Teen vaccination coverage estimates for most vaccines among adolescents aged 13–17 years. Model-based vaccination coverage estimates were notably lower for varicella, MMR, and Hepatitis B compared to NIS-Teen coverage estimates among adolescents. Trends in estimates of national vaccination coverage were similar between model-based estimates for children and adolescents as compared to NIS-Child and NIS-Teen, respectively.ConclusionsA hierarchical model applied to data from IIS may be used to estimate coverage for routinely recommended vaccines among children and adolescents and allows for timely analyses of childhood and adolescent vaccines to quickly assess trends in vaccination coverage across the United States. Monitoring real-time vaccination coverage can help promote immunizations to protect children and adolescents against vaccine-preventable diseases.     

Using models to shape measles control and elimination strategies in low- and middle-income countries: A review of recent applications

After many decades of vaccination, measles epidemiology varies greatly between and within countries. National immunization programs are therefore encouraged to conduct regular situation analyses and to leverage models to adapt interventions to local needs. Here, we review applications of models to develop locally tailored interventions to support control and elimination efforts. In general, statistical and semi-mechanistic transmission models can be used to synthesize information from vaccination coverage, measles incidence, demographic, and/or serological data, offering a means to estimate the spatial and age-specific distribution of measles susceptibility. These estimates complete the picture provided by vaccination coverage alone, by accounting for natural immunity. Dynamic transmission models can then be used to evaluate the relative impact of candidate interventions for measles control and elimination and the expected future epidemiology. In most countries, models predict substantial numbers of susceptible individuals outside the age range of routine vaccination, which affects outbreak risk and necessitates additional intervention to achieve elimination. More effective use of models to inform both vaccination program planning and evaluation requires the development of training to enhance broader understanding of models and where feasible, building capacity for modelling in-country, pipelines for rapid evaluation of model predictions using surveillance data, and clear protocols for incorporating model results into decision-making.     

Sustained measles elimination in Australia and priorities for long term maintenance

We used the 2002 national serosurvey to evaluate a primary care-based young adult vaccination campaign, measure the reproductive number (R) and, together with vaccination coverage estimates, predict R until 2012. The campaign had no impact on immunity in young adults. R was estimated to be 0.69 and predicted to stay well below the epidemic threshold of 1 until at least 2012, indicating that Australia should remain free of endemic measles in the medium term. To maintain elimination in the longer term, the timeliness and coverage of childhood vaccinations must improve and innovative strategies will be required to improve measles immunity among young adults. This experience is likely to apply to developed countries that have achieved or are approaching measles elimination.     

Estimating the number of US children susceptible to measles resulting from COVID-19-related vaccination coverage declines

Measles elimination hinges on vaccination coverage remaining above 95% to retain sufficient community protection. Recent declines in routine measles vaccinations due to the COVID-19 pandemic coupled with prior models indicating the country was close to the 92% herd immunity benchmark are a cause for concern. We evaluated population-level measles susceptibility in the US, including sensitivity analyses accounting for pandemic-related impacts on immunization. We estimated the number of children aged 0–18 currently susceptible to measles and modeled susceptibility proportions in decreased vaccination scenarios. Participants were respondents to the NIS-Teen survey between 2008 and 2017 that also had provider-verified vaccination documentation. The exposure of interest was vaccination with a measles-containing vaccine (MCV), and the age at which they were vaccinated for all doses given. Using age at vaccination, we estimated age-based probabilities of vaccination and modeled population levels of MCV immunization and immunity vs. susceptibility. Currently, 9,145,026 children (13.1%) are estimated to be susceptible to measles. With pandemic level vaccination rates, 15,165,221 children (21.7%) will be susceptible to measles if no attempt at catch-up is made, or 9,454,436 children (13.5%) if catch-up vaccinations mitigate the decline by 2–3%. Models based on increased vaccine hesitancy also show increased susceptibility at national levels, with a 10% increase in hesitancy nationally resulting in 14,925,481 children (21.37%) susceptible to measles, irrespective of pandemic vaccination levels. Current levels of measles immunity remain below herd immunity thresholds. If pandemic-era reductions in childhood immunization are not rectified, population-level immunity to measles is likely to decline further.     

Description of a large measles epidemic in Democratic Republic of Congo, 2010–2013

Background

Although measles mortality has declined dramatically in Sub-Saharan Africa, measles remains a major public health problem in countries like the Democratic Republic of Congo (DRC). Here, we describe the large measles epidemic that occurred in the Democratic Republic of Congo between 2010 and 2013 using data from the national surveillance system as well as vaccine coverage surveys to provide a snapshot of the epidemiology of measles in DRC.

Methods

Standardized national surveillance data were used to describe measles cases from 2010 to 2013. Attack rates and case fatality ratios were calculated and the temporal and spatial evolution of the epidemic described. Data on laboratory confirmation and vaccination coverage surveys as a part of routine program monitoring are also presented.

Findings

Between week 1 of 2010 and week 45 of 2013, a total of 294,455 cases and 5,045 deaths were reported. The cumulative attack rate (AR) was 0.4%. The Case Fatality Ratio (CFR) was 1.7% among cases reported in health structures through national surveillance. A total of 186,178 cases (63%) were under 5 years old, representing an estimated AR of 1.4% in this age group. Following the first mass vaccination campaigns, weekly reported cases decreased by 21.5%. Results of post-vaccination campaign coverage surveys indicated sub-optimal (under 95%) vaccination coverage among children surveyed.

Conclusions

The data reported here highlight the need to seek additional means to reinforce routine immunization as well as ensure the timely implementation of Supplementary Immunization Activities to prevent large and repeated measles epidemics in DRC. Although reactive campaigns were conducted in response to the epidemic, strategies to ensure that children are vaccinated in the routine system remains the foundation of measles control.