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 immunity over two decades in two large Italian Regions: How far is the elimination goal?

In Italy, the inclusion of measles vaccine in children immunization schedule and the promotion of national mass vaccination campaigns increased measles vaccination coverage. However, measles outbreaks continue to occur increasingly involving adolescents and adults. The aim of this study was to evaluate the prevalence to measles antibody in a sample of Italian population between 1993 and 2018.Human serum samples from subjects aged 3–40 years were collected between 1993 and 2018 and tested for measles IgG antibodies by commercial ELISA.During the study period, the 3–10-year-old age group showed the most important change, with a significant increase in 2003–2007 in both seroprevalence and IgG levels, followed by a slow decrease. The 11–18-year-old age group showed relatively stable seroprevalence rates and IgG levels over the years. The 19–30-year-old group showed stable seroprevalence rates, albeit with a decrease in IgG levels. After a significant increase in 1999–2002, the 31–40-year-old age group had high seroprevalence rates and IgG levels.Despite efforts at national level for implementing measles vaccination, a large proportion of the population is still susceptible to measles. Even if vaccination coverage increases enough to achieve the level of immunization required for herd immunity in new birth cohorts, outbreaks will continue to occur if there are immunity gaps in older age groups. Establishing policies for measles vaccination targeting adult population is needed to close immunity gaps and reach the elimination goal.     

Measles antibody levels among vaccinated and unvaccinated children 6–59 months of age in the Democratic Republic of the Congo, 2013–2014

BackgroundMeasles is endemic in the Democratic Republic of the Congo (DRC), and 89–94% herd immunity is required to halt its transmission. Much of the World Health Organization African Region, including the DRC, has vaccination coverage below the 95% level required to eliminate measles, heightening concern of inadequate measles immunity.MethodsWe assessed 6706 children aged 6–59 months whose mothers were selected for interview in the 2013–2014 DRC Demographic and Health Survey. History of measles was obtained by maternal report, and classification of children who had measles was completed using maternal recall and measles immunoglobulin G serostatus obtained from a multiplex chemiluminescent automated immunoassay dried blood spot analysis. A logistic regression model was used to identify associations of covariates with measles and seroprotection, and vaccine effectiveness (VE) was calculated.ResultsOut of our sample, 64% of children were seroprotected. Measles vaccination was associated with protection against measles (OR: 0.15, 95% CI: 0.03, 0.81) when administered to children 12 months of age or older. Vaccination was predictive of seroprotection at all ages. VE was highest (88%) among children 12–24 months of age.ConclusionOur results demonstrated lower than expected seroprotection against measles among vaccinated children. Understanding the factors that affect host immunity to measles will aid in developing more efficient and effective immunization programs in DRC.     

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.     

Measles and rubella immunity in the population of Bhutan, 2017

BackgroundIn 2017, measles elimination was verified in Bhutan, and the country appears to have sufficiently high vaccination coverage to achieve rubella elimination. However, a measles and rubella serosurvey was conducted to find if any hidden immunity gaps existed that could threaten Bhutan’s elimination status.MethodsA nationwide, three-stage, cluster seroprevalence survey was conducted among individuals aged 1–4, 5–17, and >20 years in 2017. Demographic information and children’s vaccination history were collected, and a blood specimen was drawn. Serum was tested for measles and rubella immunoglobulin G (IgG). Frequencies, weighted proportions, and prevalence ratios for measles and rubella seropositivity were calculated by demographic and vaccination history, taking into account the study design.ResultsOf the 1325 individuals tested, 1045 (81%, 95% CI 78%–85%) were measles IgG seropositive, and 1290 (97%, 95% CI 95%–99%) were rubella IgG seropositive. Rubella IgG seropositivity was high in all three age strata, but only 47% of those aged 5–17 years were measles IgG seropositive. Additionally, only 41% of those aged 5–17 years who had documented receipt of two doses of measles– or measles-rubella–containing vaccine were seropositive for measles IgG, but almost all these children were rubella IgG seropositive.ConclusionsAn unexpected measles immunity gap was identified among children 5–17 years of age. It is unclear why this immunity gap exists; however, it could have led to a large outbreak and threatened sustaining of measles elimination in Bhutan. Based on this finding, a mass vaccination campaign was conducted to close the immunity gap.     

The epidemiology of measles in Tianjin,China, 2005–2014

BackgroundMeasles incidence in China has declined over the last decade and elimination is targeted by 2020. Despite increases in routine immunization services and supplementary immunization activities (SIAs), periodic outbreaks continue to occur. In this paper, we examine measles epidemiology during 2005–2014 in Tianjin, China.MethodsMeasles case data were extracted from a web-based communicable disease surveillance system. We examined the socio-demographic characteristics of measles case patients, including age, sex, urbanicity, residency status, and vaccination history. Demographic characteristics of cases were compared with the general population.ResultsFrom January 1, 2005 to December 31, 2014, 12,466 measles cases in Tianjin were reported. Among the cases, 7179 (57.6%) were male and 5287 (42.4%) were female. Over time, more cases occurred in adults, and for the 2711 cases in 2014, the majority were either infants <1 year (558, 20.58%) or adults ≥20 years (2043, 75.36%). Municipal-wide SIAs in Tianjin occurred in 2008 and 2010 with reduction in measles cases the following year for both (189 cases in 2009, and 37 cases in 2011). The number of cases rebounded to pre-SIA levels or higher within 1–3 years following each SIA: 1990 cases in 2010 and 2711 cases in 2014. Vaccination status was reported as “none” or “unknown” for 84% of all reported measles cases.ConclusionsDespite the general decline in cases, measles outbreaks continue to occur. Although the SIAs reduce numbers in their immediate aftermath, case counts rebound 1–3 years after the intervention. Continued monitoring of cases through disease surveillance activities accompanied by targeted immunization activities, including to adults, can help ensure progress toward elimination.     

Measles susceptibility in children in Karachi, Pakistan

Measles, despite being vaccine preventable is still a major public health problem in many developing countries. We estimated the proportion of measles susceptible children in Karachi, the largest metropolitan city of Pakistan, one year after the nationwide measles supplementary immunization activity (SIA) of 2007-2008. Oral fluid specimens of 504 randomly selected children from Karachi, aged 12-59 months were collected to detect measles IgG antibodies. Measles antibodies were detected in only 55% children. The proportion of children whose families reported receiving a single or two doses of measles vaccine were 78% and 12% respectively. Only 3% of parents reported that their child received measles vaccine through the SIA. Among the reported single dose measles vaccine recipients, 58% had serologic immunity against measles while among the reported two dose measles vaccine recipients, 64% had evidence of measles immunity. Urgent strengthening of routine immunization services and high quality mass vaccination campaigns against measles are recommended to achieve measles elimination in Pakistan.     

Classification of measles cases from 2014 to 2018: Implications for progress towards measles elimination in China

Measles incidence has decreased dramatically in China due to the implement of measles-containing vaccine (MCV). However, a measles epidemic caused resurgence recently, even among vaccinated individuals. To evaluate the effectiveness of current immunization programs and discuss initiatives for the next step in measles elimination in mainland China, the characteristics of 121,969 laboratory-confirmed measles cases reported in the measles surveillance system (MSS) during 2014–2018 were analyzed according to the vaccination status of the cases in this study.Children under 2 years of age without MCV vaccination (44,424, 36.42% of all cases) and adults over 20 years of age with an unknown vaccination history (37,564, 30.80% of all cases) accounted for the majority of measles cases from 2014 to 2018. 42,425 (34.78%) of the 77,384 cases with available vaccination information were categorized as programmatically preventable. 38,840 (91.55%) of the 42,425 cases were aged ≥8 months without the MCV vaccination history. 34,959 (28.66%) cases were categorized as programmatically non-preventable, of whom 22,611 (64.68%) were too young to receive their first MCV dose, 6857 (19.61%) received their first dose and were too young to receive their second dose, 5491 (15.71%) received at least two doses of MCV.15,933 (13.06%) of the 121,969 cases had a history of MCV vaccination. Measles virus infection in cases with an MCV vaccination history mainly occurred within the first month after MCV vaccination, especially in those who received a one-dose measles vaccination. MCV vaccination could reduce the frequencies of clinical symptoms and complications of measles cases.Our study confirmed that the current measles immunization programs used in mainland China is effective in reducing the measles incidence in China. Unvaccinated infants/children aged 8–23 months and high risk susceptible adults over 20 years of age with unknown vaccination histories should be the focus groups of measles immunization activities in China in the future.     

Measles and rubella IgG seroprevalence in persons 6 month-35 years of age,Mongolia, 2016

BackgroundIn 2015–2016, Mongolia experienced an unexpected large measles outbreak affecting mostly young children and adults. After two nationwide vaccination campaigns, measles transmission declined. To determine if there were any remaining immunity gaps to measles or rubella in the population, a nationally representative serosurvey for measles and rubella antibodies was conducted after the outbreak was over.MethodsA nationwide, cross-sectional, stratified, three-stage cluster serosurvey was conducted in November-December 2016. A priori, four regional strata (Ulaanbaatar, Western, Central, and Gobi-Eastern) and five age strata (6 months-23 months, 2–7 years, 8–17 years, 18–30 years, and 31–35 years) were created. Households were visited, members interviewed, and blood specimens were collected from age-appropriate members. Blood specimens were tested for measles immunoglobulin G (IgG) and rubella IgG (Enzygnost® Anti-measles Virus/IgG and Anti-rubella Virus/IgG, Siemens, Healthcare Diagnostics Products, GmbH Marburg, Germany). Factors associated with seropositivity were evaluated.ResultsAmong 4598 persons aged 6 months to 35 years participating in the serosurvey, 94% were measles IgG positive and 95% were rubella IgG positive. Measles IgG seropositivity was associated with increasing age and higher education. Rubella IgG seropositivity was associated with increasing age, higher education, smaller household size, receipt of MMR in routine immunization, residence outside the Western Region, non-Muslim religious affiliation, and non-Kazakh ethnicity. Muslim Kazakhs living in Western Region had the lowest rubella seroprevalence of all survey participants.ConclusionsNationally, high immunity to both measles and rubella has been achieved among persons 1–35 years of age, which should be sufficient to eliminate both measles and rubella if future birth cohorts have ≥ 95% two dose vaccination coverage. Catch-up vaccination is needed to close immunity gaps found among some subpopulations, particularly Muslim Kazakhs living in Western Region.     

Predicting and comparing long-term measles antibody profiles of different immunization policies

OBJECTIVE: Measles outbreaks are infrequent and localized in areas with high coverage of measles vaccine. The need is to assess long-term effectiveness of coverage. Since 1991, no measles epidemic affecting the whole island has occurred in Taiwan, China. Epidemiological models are developed to predict the long-term measles antibody profiles and compare the merits of different immunization policies on the island. METHODS: The current measles immunization policy in Taiwan, China, is 1 dose of measles vaccine at 9 months of age and 1 dose of measles, mumps and rubella (MMR) vaccine at 15 months of age, plus a 'mop-up' of MMR-unvaccinated schoolchildren at 6 years of age. Refinements involve a change to a two-dose strategy. Five scenarios based on different vaccination strategies are compared. The models are analysed using Microsoft Excel. FINDINGS: First, making the assumption that measles vaccine-induced immunity will not wane, the predicted measles IgG seroprevalences in preschool children range from 81% (lower bound) to 94% (upper bound) and in schoolchildren reach 97-98% in all strategy scenarios. Results are dependent on the association of vaccine coverage between the first and second dose of vaccine. Second, if it is assumed that vaccine-induced antibody titres decay, the long-term measles seroprevalence will depend on the initial titres post vaccination, decay rates of antibody titres and cut-off of seropositivity. CONCLUSION: If MMR coverage at 12 months of age can reach > 90%, it would be worth changing the current policy to 2 doses at 12 months and 6 years of age to induce higher antibody titres. These epidemiological models could be applied wherever a similar stage of measles elimination has been reached.     

Measles outbreak in the Republic of the Marshall Islands, 2003

BACKGROUND: Measles is a highly contagious viral infection. Measles transmission can be prevented through high population immunity (>or=95%) achieved by measles vaccination. In the Republic of the Marshall Islands (RMI), no measles cases were reported during 1989-2002; however, a large measles outbreak occurred in 2003. Reported 1-dose measles vaccine coverage among children aged 12-23 months varied widely (52-94%) between 1990 and 2000. METHODS: RMI is a Pacific island nation (1999 population: 50,840). A measles case was defined as fever, rash, and cough, or coryza, or conjunctivitis, in an RMI resident between July 13 and November 7, 2003. A vaccination campaign was used for outbreak control. RESULTS: Of the 826 reported measles cases, 766 (92%) occurred in the capital (Majuro). There were 186 (23%) cases in infants aged <1 year and 309 (37%) of cases in persons aged >or=15 years. The attack rate was highest among infants (Majuro atoll: 213 cases/1,000 infants). Among cases aged 1-14 years, 281 (59%) reported no measles vaccination before July 2003. There were 100 hospitalizations and 3 deaths. The measles H1 genotype was identified. The vaccination campaign resulted in 93% coverage among persons aged 6 months to 40 years. Interpretation Populations without endemic measles transmission can accumulate substantial susceptibility and be at risk for large outbreaks when measles virus is imported. 'Islands' of measles susceptibility may develop in infants, adults, and any groups with low vaccine coverage. To prevent outbreaks, high population immunity must be sustained by maintaining and documenting high vaccine coverage.     

张掖市麻疹疫苗初始强化免疫效果评价及健康儿童风疹抗体水平检测

目的评价张掖市麻疹减毒活疫苗（MV）初始强化免疫（强化免疫）效果,了解健康儿童风疹抗体水平,为2012年实现消除麻疹目标采取针对性的措施提供科学依据。方法采用分层抽样法,分4个年龄组采集5个县区189名受种儿童强化免疫前后双份血清,采用酶联免疫吸附试验（ELISA）检测麻疹IgG和风疹IgG抗体。结果强化免疫前（免前）麻疹IgG抗体阳性率为96.83%、保护率为85.19%,强化免疫后（免后）阳性率为100%、保护率为97.88%,免疫成功率为100%;免后麻疹IgG抗体阳性率、保护率较免前明显升高;抗体几何平均滴度（GMT）由1：941提高到1：2974。强化免疫前后,不同年龄组、不同县区和不同免疫史儿童麻疹抗体GMT差异具有显著的统计学意义。风疹抗体总阳性率为71.96%,不同县区、不同年龄组之间风疹抗体水平存在差异。结论 MV初始强化免疫效果显著。常规免疫接种工作有待加强,亟待提高及时接种率和接种质量。今后应加强婴幼儿和幼托儿童的风疹预防控制,建议麻疹、风疹同步控制较为可行。     

Loss of maternal measles antibody during infancy in an African city

Measles epidemics with 20% of the cases under nine months of age continue to occur in Brazzaville, Congo, even though measles vaccination coverage was 77% in the 12- to 23-month age group in 1986. In order to estimate the duration of passive immunity against measles, we conducted a serologic survey of infants aged 2 to 9 months. Measles antibody was measured from capillary blood with the plaque inhibition test. An antibody titre of 40 milli-International Reference Units per ml of serum (mIRU/ml) or less was defined as seronegative. Among the 252 infants studied, the proportion with detectable antibody dropped from 95.8% at 2 months of age to 48.5% at 4 months of age, and to 8.2% in the 7-8 month age group. A simple logistic model with age as the only variable provided an excellent fit to the observed values. Between the ages of 8 and 28 weeks, there was an almost steady decline of approximately 4.7% per week in the proportion of infants who were seropositive. These findings suggest that loss of maternal measles antibody during infancy might be faster than reported in other African populations. Giving measles vaccine to infants before the age of nine months currently recommended by the Expanded Programme on Immunization may be useful in some populations. Further studies of seroconversion and impact on measles are needed.     

Waning of measles maternal antibody in infants in measles elimination settings – A systematic literature review

IntroductionMost infants are born with immunity to measles through maternal antibodies transferred in pregnancy, which decay over time. However, in measles elimination settings, where measles does not circulate endemically and most immunity is from immunization rather than infection, maternal antibody levels are lower. This results in infant immunity that wanes earlier, and a wider susceptibility gap between maternal antibody decay and infant immunization than in non-eliminated settings. We aimed to systematically quantify the extent and duration of protection from measles in infants in settings that have sustained measles elimination.MethodsWe conducted a systematic review of studies of measles maternal antibody waning in infants in measles elimination settings. We searched MEDLINE, Embase, CINAHL, Scopus, BIOSIS Previews, and Global Health databases for relevant studies. Studies were included if they were set in countries that had eliminated measles for ≥3 years, and if the study cohort included healthy, full-term, unvaccinated infants ≤12 months, born to healthy mothers, and reported a relevant measure of measles maternal antibody in infants. We assessed study quality using the MetaQAT tool.ResultsWe identified 4692 unique citations, eight of which met inclusion criteria. One study reported anti-measles antibody in cord blood, six reported antibody in infant sera, and one reported both. Two studies reported that 80 and 100% of infants were protected from measles at birth. One study reported no protection amongst 3–7 month old infants, and another reported limited protection in infants >4 months. The remaining studies reported the proportion of infants with detected antibody, but not the proportion immune.ConclusionAlthough limited, these data suggest that in settings that have sustained measles elimination, some infants are susceptible to measles well before the age of routine measles immunization. Setting-specific seroprevalence and vaccine effectiveness studies are required to evaluate this in different jurisdictions.     

Are refugees arriving in Denmark an under-immunised group for measles? A cross-sectional serology study

BackgroundIn 2018, Europe faced the highest number of Measles cases in a decade. In Denmark, the childhood vaccination programme has a coverage of approximately 90%. To eliminate the disease, vaccine coverage needs to be above the herd immunity threshold of 95%. This can be even more difficult to obtain, when vaccination programmes break down due to war, natural disasters etc. and concern has been raised, that unvaccinated refugees could facilitate spread of measles when migrating.MethodsIn order to address this concern, we tested 513 newly arrived refugees and family reunified refugees aged between 0 and 70 years for measles IgG antibodies. The participants were tested as part of a general health assessment between May 2016 and October 2018. In the cohort, 50% were males and the majority came from Syria (55%).ResultsWe found that 85% of the total group of refugees had immunity against measles. The 15% lacking antibodies were evenly distributed between the various countries of origin. Moreover, we found immunity to increase with age, leaving young children most vulnerable to infection, 79.9% (<19 years) vs 89.1% (≥19 years). Interview questions on previous vaccinations did not correlate to serology.ConclusionRefugees have measles immunity slightly lower than the host population.     

Risk factors for measles in children aged 8 months–14 years in China after nationwide measles campaign: A multi-site case-control study, 2012–2013

IntroductionEndemic measles persists in China, despite >95% reported coverage of two measles-containing vaccine doses and nationwide campaign that vaccinated more than 100 million children in 2010. In 2011, almost half of the 9943 measles cases in China occurred in children eligible for measles vaccination. We conducted a case-control study during 2012–2013 to identify risk factors for measles infection in children aged 8 months–14 years.MethodsChildren with laboratory-confirmed measles were age- and neighborhood-matched with three controls. We interviewed parents of case and control infants on potential risk factors for measles. We calculated adjusted matched odds ratios and 95% confidence intervals of risk factors. We calculated attributable fractions for risk factors that could be interpreted as causal and vaccine efficacy (VE) for the measles containing vaccine (MCV) used in the Chinese immunization program.ResultsIn all, 969 case-patients and 2845 controls were enrolled. In multivariable analysis, lack of measles vaccination both overall (mOR 22.7 [16.6, 31.1] and when stratified by region (east region, mOR 74.2 [27.3, 202]; central/western regions mOR 17.4 [12.5, 24.3]), hospital exposure (mOR 63.0, 95% CI [32.8, 121]), and migration among counties (overall mOR 3.0 [2.3, 3.9]) were significant risk factors. The calculated VE was 91.9–96.1% for a single dose of MCV and 96.6–99.5% for 2 doses.ConclusionsLack of vaccination was the leading risk factor for measles infection, especially in children born since the 2010 supplementary immunization activity. Reducing missed vaccination opportunities, improving immunization access for migrant children, and strengthening school/kindergarten vaccine checks are needed to strengthen the routine immunization program and maintain progress toward measles elimination in China.     

African-American children are at risk of a measles outbreak in an inner-city community of Chicago, 2000

BACKGROUND: Since the measles resurgence of 1989-1991, which affected predominantly inner-city preschoolers, national vaccination rates have risen to record-high levels, but rates among inner-city, preschool-aged, African-American children lag behind national rates. The threat of measles importations from abroad exists and may be particularly important in large U.S. cities. To stop epidemic transmission, measles vaccination coverage should be at least 80%. OBJECTIVE: To determine measles vaccination rates and predictors for having received a dose of measles-containing vaccine by age 19 to 35 months among children in an inner-city community of Chicago.METHODS: We used a cross-sectional survey with probability proportional to size cluster sampling. Immunization histories from parent-held records and providers were combined to establish a complete vaccination history. RESULTS: A total of 2545 households were contacted, and 170 included a resident child aged 12 to 35 months. Of these, 97% (N=165 children) agreed to participate. Immunization history from a parent or provider was not available for 20 children. Among children aged 19 to 35 months with available immunization histories, 74% received measles vaccine (n=100); of these, 84% received the vaccine as recommended at ages 12 to 15 months. However, when including children without immunization histories, measles coverage levels among children aged 19 to 35 months were 64% (n=114). Among children with records, predictors for receipt of measles vaccine by age 19 to 35 months were possessing a hand-held immunization card (odds ratio [OR]=16.8; 95% confidence interval [CI]=4.2-67.1); utilizing a public health department provider for a usual source of care (OR=8.9; 95% CI=1.6-47.2); and being up-to-date for vaccines at 3 months of age (OR=5.0; 95% CI=1.8-14.1). CONCLUSIONS: Optimistically assuming that children without immunization histories are as well immunized as children with immunization histories, the measles vaccination rate among Englewood's children aged 19 to 35 months is too low to maintain immunity (74%). Measles coverage levels lagged behind coverage reported in a national survey in Chicago (86%) and the nation as a whole (92%). Efforts to raise and sustain coverage should be undertaken.     

Measles susceptibility in maternal-infant dyads—Bamako,Mali

Measles is endemic in Africa; measles mortality is highest among infants. Infant measles antibody titer at birth is related to maternal immune status. Older mothers are likelier to have had measles infection, which provides higher antibody titers than vaccine-induced immunity. We investigated the relationship between maternal age and measles susceptibility in mother-infant pairs in Mali through six months of infancy.We measured serum measles antibodies in 340 mother-infant pairs by plaque reduction neutralization test (PRNT) and calculated the proportion of mothers with protective titers (>120 mIU/mL) at delivery and the proportion of infants with protective titers at birth, and at three and six months of age. We explored associations between maternal age and measles antibodies in mothers and infants at the timepoints noted.Ten percent of Malian newborns were susceptible to measles; by six months nearly all were. Maternal and infant antibody titers were highly correlated. At delivery, 11% of mothers and 10% of newborns were susceptible to measles. By three and six months, infant susceptibility increased to 72% and 98%, respectively. Infants born to younger mothers were most susceptible at birth and three months. Time to susceptibility was 6.6 weeks in infants born to mothers with measles titer >120–<430 mIU/mL versus 15.4 weeks when mothers had titers ≥430 mIU/mL.Maternal and newborn seroprotective status were positively correlated. Improved strategies are needed to protect susceptible infants from measles infection and death. Increasing measles immunization coverage in vaccine eligible populations, including nonimmune reproductive-aged women and older children should be considered.     

麻疹胎传抗体的跟踪观察及初免月龄的探讨

目的：通过了解婴儿胎传抗体衰减情况和不同月龄婴儿对麻疹疫苗的免疫应答情况,探讨减少小月龄麻疹病例的对策。方法：采用ELESA方法测定血清中麻疹IgG抗体水平。月龄时降低50％,6月龄和8月龄降到15％左右,几乎无保护作用,且6月龄和8月龄婴儿接种疫苗后免疫成功率间无差别。结论：目前新生儿麻疹抗体水平低,到6月龄时大部分婴儿胎传抗体已降到保护水平以下,因此,为实现消灭麻疹的总目标,在小月龄麻疹发病率高的地区可考虑将麻疹初免月龄从8月龄提前到6月时进行。     

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.