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.     

Trend of immunity against measles and varicella zoster virus in healthcare workers in Korea

ObjectiveTo examine the seroprevalence of measles and varicella zoster virus (VZV) among healthcare workers (HCW) and evaluate the concordance between self-reported history of previous disease or vaccination and seropositivity.DesignA seroprevalence study and survey.SettingA university-affiliated tertiary care hospital.ParticipantsAll HCWs working in high-risk services in 2017 underwent serologic tests and survey; all new HCWs employed in the subsequent years, serologic tests only.MethodsA serologic study was conducted using chemiluminescence immunoassay (2017) or enzyme immunoassays (2018 and later). HCWs who underwent serological testing in 2017 completed a self-administered questionnaire on their history of infection and vaccination.ResultsA total of 10,278 and 9607 HCWs underwent serologic tests for measles and VZV IgG, respectively, from 2017 to 2022. The overall seropositivity rates for measles and VZV were 78.1 % and 92.8 %, respectively. Measles seropositivity declined gradually from >90 % in the HCWs born in the 1960s to <80 % in those born in the 1990s. There was a significant difference in measles seropositivity between the birth cohorts (BCs) 1967–1984 and 1985–1999 (P < 0.001; odds ratio, 1.16; 95 % confidence interval, 1.14–1.18). The seropositivity for VZV was stable, at >90 % in all BCs. The self-reported vaccination history was not independently associated with seropositivity, and the negative predictive value of the survey was very low (9.6 % and 13.1 %, respectively).ConclusionsMeasles seropositivity showed a substantial decline among HCWs born in 1985 or later, while varicella seropositivity remained high. The self-reported vaccination history was not sufficiently reliable for screening HCWs.     

A population profile of measles susceptibility in Tianjin,China

BackgroundMeasles is a highly infectious illness requiring herd immunity of 95% to interrupt transmission. Measles is targeted for elimination in China, which has not reached elimination goals despite high vaccination coverage. We developed a population profile of measles immunity among residents aged 0–49 years in Tianjin, China.MethodsParticipants were either from community population registers or community immunization records. Measles IgG antibody status was assessed using dried blood spots. We examined the association between measles IgG antibody status and independent variables including urbanicity, sex, vaccination, measles history, and age.Results2818 people were enrolled. The proportion measles IgG negative increased from 50.7% for infants aged 1 month to 98.3% for those aged 7 months. After 8 months, the age of vaccination eligibility, the proportion of infants and children measles IgG negative decreased. Overall, 7.8% of participants 9 months of age or older lacked measles immunity including over 10% of those 20–39 years. Age and vaccination status were significantly associated with measles IgG status in the multivariable model. The odds of positive IgG status were 0.337 times as high for unvaccinated compared to vaccinated (95% CI: 0.217, 0.524).ConclusionsThe proportion of persons in Tianjin, China immune to measles was lower than herd immunity threshold with less than 90% of people aged 20–39 years demonstrating protection. Immunization programs in Tianjin have been successful in vaccinating younger age groups although high immunization coverage in infants and children alone would not provide protective herd immunity, given the large proportion of non-immune adults.     

Pediatric measles cases by residence status in Tel Aviv,Israel

BackgroundMeasles is a vaccine-preventable infectious disease whose outbreaks generally originate from exposure to populations with low vaccination coverage.MethodsThis study compared the rates and morbidity of measles cases in the district of Tel-Aviv during two outbreaks (2012 and 2018–2019) by citizenship and geographic location.ResultsThere were 67 pediatric cases reported in 2012 and 222 in 2018–2019. Cases were more likely to have pneumonia in 2012 as compared to in 2018–2019 (58.2% versus 6.3%) and less likely to report a single vaccination dose (9.5% versus 22.8%, respectively). In 2012, the majority of cases were among children without legal residence (CWLR), while in 2018–2019, they were the minority of cases (N = 54, 80.6% versus N = 51, 23.0%, respectively). In both outbreaks, CWLR were more likely to be less than one year old (the recommended age for the first dose of measles vaccination), unvaccinated or with unknown vaccine status, to be treated in a tertiary care center, and to have pneumonia than children with Israeli citizenship (CC). In both outbreaks, CWLR lived in a concentrated neighborhood in Southern Tel Aviv.ConclusionWhile the two measles outbreaks differed in overall morbidity, in both outbreaks CWLR presented with a more severe clinical presentation and were less likely to be vaccinated (in part due to their younger age) than CC. The geographically concentration of CWLR was distinct from that of the CC in both outbreaks. Healthcare professionals should promote vaccination uptake and increase parents' awareness to early signs of the disease.     

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.     

Seroprevalence of measles and rubella antibodies in pregnant women Haiti, 2012

Background

Haiti had set a national goal to eliminate measles and rubella, as well as congenital rubella syndrome (CRS) by 2010. A 2007–2008 nationwide measles and rubella vaccination campaign targeting 1–19 years, however, reached only 79% of the target population. To assess whether population immunity was adequate to support elimination, we conducted a national serosurvey.

Methods

We systematically selected 740 serum specimens collected from pregnant women in a 2012 national antenatal HIV sentinel serosurvey across four age strata: 15–19, 20–24, 25–29 and 30–39 years. Sera were tested for measles and rubella specific immunoglobulin G antibodies (IgG) using commercial immunoassays. We classified sera as seropositive, seronegative or indeterminate per manufacturer's instructions, and analyzed seroprevalence according to age strata, and rural or urban residence. We assessed immunity by estimating antibody concentrations in international units per milliliter (IU/mL) for seropositive and indeterminate sera. Measles IgG concentrations >0.12 IU/mL and rubella IgG concentrations >10 IU/mL were considered clinically protective.

Results

Of 740 sera, 696 (94.1%) were seropositive and 20 (2.7%) were indeterminate for measles IgG; overall 716 (96.8%) sera had IgG concentrations >0.12 IU/mL. For rubella IgG, 691 (93.4%) sera were seropositive and 1 (0.1%) was indeterminate; a total of 687 (92.8%) had IgG concentrations >10 IU/mL. Measles seropositivity varied across age strata (p = 0.003); seropositivity increased from 88.6% among 15–19 year olds to 98.4% among 30–39 year olds (Cochran–Armitage trend test ≤ 0.0001). Rubella seropositivity did not differ across age strata. There were no statistically significant differences in measles or rubella seropositivity by urban versus rural residence.

Conclusion

Despite previous low vaccination coverage for measles, results from this serosurvey indicate high levels of measles and rubella seropositivity in pregnant women, and contribute to the evidence for measles, rubella and CRS elimination from Haiti by the target date.     

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.     

Seroepidemiology of pertussis in China: A population-based,cross-sectional study

BackgroundDespite high pertussis vaccination coverage and significant decrease of pertussis since the adoption of the Expanded Programme on Immunization (1978), increased pertussis incidence has been reported in China from 2013 to 2017. This study aimed at evaluating the immune response to pertussis among vaccinated children and beyond in China.MethodsThe study recruited 2 144 healthy subjects. Serum IgG antibodies against pertussis toxin (anti-PT IgG) were measured by ELISA. Anti-PT IgG concentration (GMC), seropositivity rate (GMC ≥ 40 IU/ml), and recent infection rate (GMC > 100 IU/ml) were calculated. Participants ≤ 2 years-old were further stratified by vaccination schedule intervals and participants ≤ 6 years-old by vaccine used (Domestic DTaP or DTaP-IPV//PRP ~ T (Pentaxim, SP)).ResultsAmong 0–6-year-olds, the anti-PT IgG GMC was 5.99 IU/ml (95%CI 5.39–6.67). The GMC increased in accordance with the primary vaccination series (4–6 months) and the toddler booster (18–23 months), and continuously declined thereafter to its nadir at 6 years-old [3.72 IU/ml (95%CI 2.91–4.77)]. GMCs were markedly higher in those vaccinated with DTaP-IPV/PRP ~ T compared to DTaP. In individuals > 6 years-old, the GMC was 5.67 IU/ml (95%CI 5.36–6.00), the seropositivity rate was 6.7% (95%CI 5.5–7.9) and the recent infection rate was 1.2% (95%CI 0.7–1.7). The seropositivity rates increased from 6 years-old and peaked at 9 years-old (10.3% [95%CI 0.7–19.8]).ConclusionsVaccination against pertussis increases anti-PT IgG, but wanes over time. The sero-estimated infection rates increase from school age and peak at about 9 years-old. These results support the addition of a booster of pertussis vaccine at preschool age.     

An increasing,potentially measles-susceptible population over time after vaccination in Korea

BackgroundIn Korea, measles occurs mainly in infants <12 months of age, who are unvaccinated. In addition, vaccine populations, including adolescents and young adults, can become infected though importation. Thus, the question arises whether the current level of herd immunity in Korea is now insufficient for protecting against measles infection.MethodsAge-specific measles seroprevalence was evaluated by performing enzyme immunoassays and plaque reduction-neutralization tests on 3050 subjects aged 0–50 years (birth cohort 1964–2014) and 480 subjects aged 2–30 years (birth cohort 1984–2012).ResultsThe overall seropositivity and measles antibody concentrations were 71.5% and 1366 mIU/mL, respectively. Progressive decline in antibody levels and seropositivity were observed over time after vaccination in infants, adolescents, and young adults. The accumulation of potentially susceptible individuals in the population was confirmed by comparing data from 2010 and 2014 seroprevalence surveys. The statistical correlation between measles incidence and measles seronegativity was determined.ConclusionsWaning levels of measles antibodies with increasing time post-vaccination suggests that measles susceptibility is potentially increasing in Korea. This trend may be related to limitations of vaccine-induced immunity in the absence of natural boosting by the wild virus, compared to naturally acquired immunity triggered by measles infection. This study provides an important view into the current measles herd immunity in Korea.     

Persistence of measles antibodies,following changes in the recommended age for the second dose of MMR-vaccine in Portugal

In populations vaccinated with two doses of combined measles–mumps–rubella vaccine (MMR), the serum levels of antibodies against measles depend on the vaccination schedule, time elapsed from the last dose and the area-specific epidemiological situation. Variables measuring “schedule” are age at first and second doses of MMR and intervals derived from that. Changes in vaccination schedules have been made in Portugal. The specific objectives of this study were to measure the association between those potential determinants and the concentration of measles-specific IgG antibodies, after the second dose of MMR. Convenience samples of three Portuguese birth cohorts were selected for this study (41, 66 and 60 born, respectively, in 2001–2003, 1990–1993 and 1994–1995). Geometric mean concentrations (GMC) for measles IgG were, respectively, 934, 251 and 144 mIU/ml; p < 0.001). Anti-measles-IgG serum concentration decreased with time since last vaccination (waning immunity) and was not influenced by any other component of vaccination schedule, namely age at vaccination with the second dose of MMR. Waning levels of measles antibodies have been observed elsewhere but not as fast as it was observed in Portuguese birth cohorts in this study. Changes in the vaccination schedules might have to be considered in the future.     

Effect of early measles vaccination on long-term protection: A systematic review

BackgroundIn North America, the first dose of a measles-containing vaccine (MCV1) is administered at ≥12 months of age. However, MCV1 may be given to infants <12 months living in highly endemic areas or traveling to these areas. Although an early dose of MCV1 leads to immediate protection, it remains unclear how this impacts long-term immunity.MethodsThis systematic review and meta-analysis evaluates the impact of MCV1 given at <12 months vs. ≥12 months of age on long-term immunogenicity and vaccine effectiveness, with long-term defined as at least one-year post-vaccination. PubMed, EMBASE, Global Health, Web of Science and Scopus were searched on October 31st, 2019. Studies were included if they included a cohort of infants vaccinated <12 months of age and evaluated long-term immunogenicity, vaccine efficacy, or effectiveness.ResultsA total of 51 texts were identified: 23 reported outcomes related to vaccine effectiveness and 30 to immunogenicity. Infants vaccinated with MCV1 < 12 months of age showed an overall higher risk of measles compared to ≥12 months of age (RR = 3.16, 95% CI: 2.00, 5.01; OR = 2.46, 95% CI: 1.40, 4.32). Risk of measles decreased with increasing age at first vaccination, with those vaccinated with one dose ≥15 months at a lesser risk compared to 12–14 months or <12 months. Measles seroconversion and seropositivity was not affected by age at first vaccination, but antibody levels were significantly lower in the MCV1 < 12-month group (MD = −0.40, 95% CI: −0.71, −0.09).ConclusionLong-term measles seroconversion and seropositivity did not appear to be affected by age at MCV1, while vaccine effectiveness decreased with younger age. There was not enough evidence to look at the effect of age at MCV1 on immune blunting.     

Measles seroprevalence in Chiradzulu district,Malawi: Implications for evaluating vaccine coverage

IntroductionSelf-reported measles vaccination coverage is frequently used to inform vaccination strategies in resource-poor settings. However, little is known to what extent this is a reliable indicator of underlying seroprotection, information that could provide guidance ensuring the success of measles control and elimination strategies.MethodsAs part of a study exploring HIV infection and measles susceptibility, we conveniently sampled consenting HIV-uninfected patients presenting at the HIV voluntary counselling and testing centre, and HIV-infected patients presenting for regular care, in Chiradzulu district hospital, Malawi, between January and September 2012.ResultsA total of 2106 participants were recruited between January and September 2012, three quarters of whom were HIV positive. Vaccination cards were available for just 7 participants (0.36%). 91.9% of participants were measles seropositive.Older age (OR = 1.11 per year increase in age; 95%CI: 1.09–1.14) and being female (OR = 1.90; 95%CI: 1.26–2.87) were both associated with significantly increased odds for seroprotection. Prior vaccination history was associated with lower odds (Odds Ratio (OR) = 0.44; 95% confidence interval (CI): 0.22–0.85) for confirmed seropositivity. Previous measles infection was not significantly associated with seroprotection (OR = 1.31; 95%CI: 0.49–3.51).Protection by history and serological status were concordant for 64.3% of participants <35 years old. However, analysis by age group reveals important differences in concordance between the ages, with a greater degree of discordance among younger ages.Vaccination and/or infection history as a predictor of seropositivity was 75.8% sensitive, but just 10.3% specific.ConclusionReported vaccination and previous infection were poor predictors of seropositivity, suggesting these may be unreliable indicators of seroprotection status. Such serosurveys may be indicated in similar settings in which overestimation of the proportion of seroprotected individuals could have important ramifications if used to guide vaccination strategies.     

Is there an association between socioeconomic status and immune response to infant and childhood vaccination in the Netherlands?

IntroductionSocioeconomic status (SES) is a well-known determinant of health, but its relation with vaccine-induced immunity is less documented. We explored the association between SES and immunoglobulin G (IgG) levels against vaccine-preventable diseases in vaccinated children in the Dutch National Immunization Programme.MethodsData from a population-wide cross-sectional serosurvey in the Netherlands (2006–2007) were used. We compared geometric mean IgG concentrations/titers (GMC/T ratios) against measles, mumps, rubella, Haemophilus influenzae type b (Hib), Neisseria meningococcus type C, diphtheria, tetanus, poliovirus types 1,2,3 and pertussis in children of high versus low SES by linear regression analysis. We included 894 children (0–12 years) at one of two timeframes: 1 month to 1 year, or 1–3 years after vaccination. Mother’s educational level and net household income served as binary indicators of SES.ResultsOf 58 possible associations of vaccine-induced antibody responses with educational level and 58 with income, 10 (9%) were statistically significant: 2 favouring (that is, with higher IgG levels at) high educational level (for Hib 1 m-1y after vaccination (GMC/T ratio: 2.99, 95%CI: 1.42–6.30) and polio 2 1 m-1y after the 9-year booster dose (1.14, 1.01–1.27)) and 8 favouring low income (polio 1, 2 and 3 1 m-1y after the 11-month booster (0.74, 0.58–0.94; 0.79, 0.64–0.97; 0.72, 0.55–0.95), polio 3 and pertussis 1-3y after the 11-month booster (0.70, 0.56–0.88; pertussis-prn: 0.60, 0.37–0.98; pertussis-ptx: 0.66, 0.47–0.95), mumps and rubella 1-3y after first vaccination (0.73, 0.55–0.97; 0.70, 0.55–0.90), and rubella 1 m-1y after second vaccination (0.83, 0.55–0.90)). After adjustment for multiple testing, none of the differences remained significant. There was no association between SES and proportion of children with protective IgG levels.ConclusionIn this explorative study, we found no consistent association between SES and immune response to vaccination in the Netherlands and no association with protective IgG levels. Additional studies in other settings should confirm this finding.     

A hospital-associated measles outbreak among individuals not targeted for vaccination in eastern China, 2014

BackgroundAn outbreak of measles occurred in early 2014 among individuals not targeted for vaccination—adults, and infants too young to vaccinate, in Xiangshan County, Zhejiang Province, in eastern China.ObjectiveWe conducted an investigation to identify risk factors responsible for this outbreak and to provide evidence-based recommendations for measles elimination strategies in China.MethodsMeasles was diagnosed using national standard case definitions. In a case-control study, 20 randomly selected measles patients were matched with controls selected from the same village or community as each case in a 1:2 case-to-control ratio. Controls were matched on age, within 5 years, and gender. We compared exposure histories during the 7–21 days before rash onset of the case and the same time period for the matched controls. We also conducted a measles antibody seroprevalence survey of a convenient sample of residual serum obtained from healthy patients during routine care in a hospital.ResultsThe outbreak consisted of 45 measles cases, with an attack rate of 8.9/100,000 total population. Among cases, 91.1% (41/45) were adults (ranged 23–51 years) who had unknown vaccination histories; the other cases were infants younger than 8 months of age. The case-control study showed major risk factors to be a visit to Hospital X (OR_MH = 7.3, 95% CI: 1.8–30.7) and treatment in an IV room in Hospital X (OR_MH = 11.0, 95% CI: 1.3–96.1). The seroprevalence survey showed that 88.8% of adults had measles IgG antibodies, and that 100% of children 2–19 years of age were seropositive.ConclusionsThe outbreak was primarily among age groups not targeted for vaccination—primarily adults, but with some children too young to vaccinate. Visiting a hospital was the major risk factor for measles transmission. We conclude that in addition to maintaining high 2-dose coverage with measles vaccine, working with hospital infection control programs to implement evidence-based strategies to prevent or limit hospital transmission is an important action for eliminating measles in eastern China.     

Measles clinical presentation,hospitalization and vaccination status among children in a community-wide outbreak

BackgroundIn 2018–2019, a measles outbreak emerged in Israel (4158 notified cases). We aimed to evaluate the measles characteristics and the vaccination status among children during the outbreak.MethodsWe performed a cross-sectional study of measles cases in children under 18 years, residing in the Jerusalem district (2254 notified measles cases, June 2018-May 2019). The variables included: clinical symptoms (fever, rash, cough, coryza, conjunctivitis), hospitalizations and child’s vaccination status. The national measles vaccination schedule includes two vaccine doses (at ages 12 months and 6 years).ResultsChildren, under 18 years, comprised 79% (1782/2254) of the notified measles cases. The hospitalization rate was 6.6%. There was one fatality. The measles vaccination status was analyzed by age groups. Infants under 12 months (n = 425) were excluded. Children aged 1–5 years (n = 785) and 6–17 years (n = 572) were expected to receive 1 and 2 measles vaccine doses, respectively. Most (88%) children (1–17 years) were unvaccinated, 138 received 1 measles vaccine dose and 24 received 2 doses. Of children aged 1–5 years 106 (13.5%) received 1 vaccine dose and were compared to unvaccinated children. Vaccinated children showed lower rates of clinical symptoms and lower risk for hospitalization compared to unvaccinated children (Odds ratio: OR = 4.8, 95%CI 1.12–20.2). Vaccine effectiveness of 79% was estimated for one measles vaccine dose against hospitalization.ConclusionsData on vaccine effectiveness reflect how well vaccines protect children against infection and morbidity. We evaluated the real-world effectiveness of measles vaccine, in an outbreak setting, and showed reduced morbidity in once-vaccinated children.     

Field evaluation of measles vaccine effectiveness among children in the Democratic Republic of Congo

BackgroundLarge-scale measles outbreaks in areas with high administrative vaccine coverage rates suggest the need to re-evaluate measles prevention and control in the Democratic Republic of Congo (DRC). Monitoring of measles Vaccine Effectiveness (VE) is a useful measure of quality control in immunization programs. We estimated measles VE among children aged 12–59 months in the Democratic Republic of Congo (DRC) using laboratory surveillance data from 2010–2012.MethodsWe used the case-based surveillance system with laboratory confirmation to conduct a case-control study using the test negative design. Cases and controls were selected based on presence (n = 1044) or absence (n = 1335) of measles specific antibody IgM or epidemiologic linkage. Risk factors for measles were assessed using unconditional logistic regression, stratified by age.ResultsAmong children 12–59 months, measles vaccination was protective against measles [aOR (95% C)], 0.20 (0.15–0.26) and estimated VE was 80% (95% CI 74–85%). Year of diagnosis, 2011: 6.02 (4.16–8.72) and 2012; 8.31 (5.57–12.40) was a risk factor for measles when compared to 2010. Compared to Kinshasa, children in Bas-Congo, Kasai-Oriental, Maniema and South Kivu provinces all had higher odds of developing measles. Measles VE was similar for children 12–23 months and 24–59 months (80% and 81% respectively).ConclusionsRepeated occurrences of measles outbreaks and lower than expected VE estimates suggest the need to further evaluate measles vaccine efficacy and improve vaccine delivery strategies in DRC.     

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 infection in persons with secondary vaccine failure,New York City, 2018–19

A large measles outbreak in New York City, which included cases among vaccinated persons and adults presumed to be immune, provided the opportunity to better understand vaccine failure and the potential impact on measles transmission. Immunoglobulin G (IgG) avidity can distinguish primary (low avidity IgG, indicating no evidence of prior immunity) versus secondary vaccine failure (high avidity IgG, indicating prior immune response and waning antibody). Measles IgG avidity was measured on samples from 62 persons: avidity was high in 53 (16 vaccinated and 37 with unknown vaccination history) and low in 9 (1 recently vaccinated and 8 with unknown vaccination history). Secondary transmission from 2 persons with high-avidity IgG results occurred. These findings illustrate that in settings of sustained measles elimination, measles infection and transmission can occur in persons with secondary vaccine failure, underscoring the need to maintain a high index of suspicion for measles during an outbreak despite prior or presumed prior vaccination.     

Seroprevalence of meningococcal ACWY antibodies across the population in the Netherlands: Two consecutive surveys in 2016/17 and 2020

BackgroundMeningococcal serogroup C (MenC) vaccination was introduced for 14-month-olds in the Netherlands in 2002, alongside a mass campaign for 1–18 year-olds. Due to an outbreak of serogroup W disease, MenC vaccination was replaced for MenACWY vaccination in 2018, next to introduction of a booster at 14 years of age and a catch-up campaign for 14–18 year-olds. We assessed meningococcal ACWY antibodies across the Dutch population in 2016/17 and 2020.MethodsIn a nationwide cross-sectional serosurvey in 2016/17, sera from participants aged 0–89 years (n = 6886) were tested for MenACWY-polysaccharide-specific (PS) serum IgG concentrations, and functional MenACWY antibody titers were determined in subsets. Moreover, longitudinal samples collected in 2020 (n = 1782) were measured for MenACWY-PS serum IgG concentrations.ResultsMenC antibody levels were low, except in recently vaccinated 14–23 month-olds and individuals who were vaccinated as teenagers in 2002, with seroprevalence of 59% and 20–46%, respectively. Meningococcal AWY antibody levels were overall low both in 2016/17 and in 2020. Naturally-acquired MenW immunity was limited in 2020 despite the recent serogroup W outbreak.ConclusionsThis study demonstrates waning of MenC immunity 15 years after a mass campaign in the Netherlands. Furthermore, it highlights the lack of meningococcal AWY immunity across the population and underlines the importance of the recently introduced MenACWY (booster) vaccination.     

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.