National Measles Research Articles

Possible Paths to Measles Eradication: Conceptual Frameworks, Strategies, and Tactics.

Measles elimination refers to the interruption of measles virus transmission in a defined geographic area (e.g., country or region) for 12 months or more, and measles eradication refers to the global interruption of measles virus transmission. Measles eradication was first discussed and debated in the late 1960's shortly after the licensure of measles vaccines. Most experts agree that measles meets criteria for disease eradication, but progress toward national and regional measles elimination has slowed. Several paths to measles eradication can be described, including an incremental path through country-wide and regional measles elimination and phased paths through endgame scenarios and strategies. Infectious disease dynamic modeling can help inform measles elimination and eradication strategies, and all paths would be greatly facilitated by innovative technologies such as microarray patches to improve vaccine access and demand, point-of-contact diagnostic tests to facilitate outbreak responses, and point-of-contact IgG tests to identify susceptible populations. A pragmatic approach to measles eradication would identify and realize the necessary preconditions and clearly articulate various endgame scenarios and strategies to achieve measles eradication with an intensified and coordinated global effort in a specified timeframe, i.e., to "go big and go fast". To encourage and promote deliberation among a broad array of stakeholders, we provide a brief historical background and key considerations for setting a measles eradication goal.

Assessing seropositivity of MMR antibodies in individuals aged 2–22: evaluating routine vaccination effectiveness after the 2003 mass campaign-a study from Iran’s National Measles Laboratory

Background and purposeThe seroprevalence of antibodies against measles, mumps, and rubella (MMR) was evaluated 17 years following a mass vaccination campaign in individuals aged 2 to 22 years who had received routine immunization but were not eligible for an extended immunization program.MethodsSamples were acquired from Iran’s National Measles Laboratory (NML), with individuals showing positive IgM results excluded. Out of the samples collected in 2020, a random selection of 290 serum samples was chosen, representing individuals between the ages of 2 and 22 years from diverse regions in the country. These samples were subjected to analysis using an enzyme-linked immunosorbent assay (ELISA) to quantify specific IgG antibodies against MMR.ResultsThe seroprevalence rates of antibodies for measles, mumps, and rubella were determined to be 76.2%, 89.3%, and 76.9%, respectively. Younger age groups exhibited higher seropositivity rates for measles and mumps, whereas the 7- to 11-year-old group demonstrated the highest seropositivity rate for rubella. A reduction in antibody status was observed from younger to older age groups, particularly those aged 17–22.ConclusionThe study unveiled suboptimal antibody levels for measles and rubella, highlighting the necessity for further investigation and potential adjustments to future vaccination strategies. Moreover, the decline in antibody status post-vaccination can accumulate in seronegative individuals over time, elevating the risk of outbreaks.

Co-circulation of two Alphaviruses in Burkina Faso: Chikungunya and O'nyong nyong viruses.

Chikungunya virus (CHIKV) and O'nyong nyong virus (ONNV) are phylogenetically related alphaviruses in the Semliki Forest Virus (SFV) antigenic complex of the Togaviridae family. There are limited data on the circulation of these two viruses in Burkina Faso. The aim of our study was to assess their circulation in the country by determining seroprevalence to each of the viruses in blood donor samples and by retrospective molecular and serological testing of samples collected as part of national measles and rubella surveillance. All blood donor samples were analyzed on the Luminex platform using CHIKV and ONNV E2 antigens. Patient samples collected during national measles-rubella surveillance were screened by an initial ELISA for CHIKV IgM (CHIKjj Detect IgM ELISA) at the national laboratory. The positive samples were then analyzed by a second ELISA test for CHIKV IgM (CDC MAC-ELISA) at the reference laboratory. Finally, samples that had IgM positive results for both ELISA tests and had sufficient residual volume were tested by plaque reduction neutralization testing (PRNT) for CHIKV and ONNV. These same patient samples were also analyzed by rRT-PCR for CHIKV. Among the blood donor specimens, 55.49% of the samples were positive for alphaviruses including both CHIKV and ONNV positive samples. Among patient samples collected as part of national measles and rubella surveillance, 3.09% were IgM positive for CHIKV, including 2.5% confirmed by PRNT. PRNT failed to demonstrate any ONNV infections in these samples. No samples tested by RT-qPCR. had detectable CHIKV RNA. Our results suggest that CHIKV and ONNV have been circulating in the population of Burkina Faso and may have been confused with malaria, dengue fever or other febrile diseases such as measles or rubella. Our study underscores the necessity to enhance arbovirus surveillance systems in Burkina Faso.

Decadal analysis of measles epidemiological data in India (2011–2020)

BackgroundDespite India being one of the largest contributors to the measles burden, crucial epidemiological information is significantly lacking. We have analyzed the national-level representative data between 2011 and 2020 to estimate the national- and state-level incidence, first dose vaccine coverage, and mortality; and developed a prediction model to examine the trend of the disease.MethodsWe extracted the Health Management Information System (HMIS) for monthly aggregated measles cases, deaths, and child immunization (9–11 months) for first dose measles vaccine coverage across all states & Union Territories (UT). Population information & projections were extracted based on Census 2011. A multilevel fixed effect panel data model was used to predict measles incidence rate, assuming measles vaccination coverage as a predictor while accounting for time fixed effects.ResultsTotal 558,536 measles cases and 4209 measles deaths were reported in India between 2010 and 2020. The incidence rate was highest in 2013 (628.8/million population), followed by a significant decline to reach 52.0/million in 2020. Measles vaccination coverage for the first dose was 84.1% in 2011 to 91.3% in 2019. Higher vaccination coverage was significantly correlated (r = 0.7, p = 0.02) with decline of measles incidence rate. The case fatality rate (CFR) was least in 2014 (0.13%) but upsurged consistently reaching to 3.3% in 2020. The predictive model indicates that with a first-dose vaccine coverage of 93.5%, and keeping other factors constant, the national measles incidence is projected to reach zero by 2025.ConclusionMeasles incidence is declining in India due to higher vaccination coverage, yet the rise in death rates emphasizes the need for continued collaborative efforts to achieve a measles-free nation.

Case Ascertainment of Measles during a Large Outbreak-Laboratory Compared to Epidemiological Confirmation.

Measles is a highly contagious viral disease, and hence, sufficient herd immunity is obligatory to prevent infection transmission. Measles is still a cause of considerable disease burden globally, mainly in children. During a national measles outbreak in Israel in 2018-2019, the peak incidence rates occurred in the Jerusalem district. Most measles cases in the Jerusalem district (75.5%, 1702) were observed in children younger than 15 years of age, 49.2% (1109) were in children under 5 years of age, and 18.9% (425) were in infants under 1 year of age. The routine measles vaccination schedule includes two doses at 1 and 6 years of age. Most cases (1828, 81.1%) were unvaccinated (zero measles vaccine doses). These cases comprised the 425 affected infants under 1 year of age, who were ineligible for vaccination, along with the 1403 children over 1 year of age, who were otherwise unvaccinated. This study aimed to describe the epidemiologic and laboratory features of this measles outbreak, and to investigate case ascertainment (laboratory confirmed compared to epidemiologically confirmed cases). The study population included 2254 measles cases notified during the period spanning June 2018 to May 2019 in the Jerusalem district (incidence rate 176 per 10,000 population). Of the 2254 cases, 716 (31.8%) were laboratory confirmed, and 1538 (68.2%) were confirmed as epidemiologically linked. Most laboratory confirmed cases (420, 58.7%) underwent real-time PCR tests. Serological tests (measles IgM and IgG) were used in 189 (26.4%) cases, and a combination of RT-PCR and serology was used in 107 (14.9%) cases. In a multivariate model analysis, the variables significantly associated (after adjustment) with higher odds for laboratory confirmation included month of disease onset (late), additional measles cases in the household (single case), place of medical treatment (hospital; either emergency department, or hospitalization) and vaccination status (at least one prior vaccine dose). The measles outbreak described demonstrates the urgency of addressing vaccination gaps with appropriate outbreak prevention programs. The road to measles elimination needs to be paved with robust public health infrastructure, excellent field epidemiology for outbreak surveillance, investigation, and control, and laboratory proficiency.

A measles IgM rapid diagnostic test to address challenges with national measles surveillance and response in Malaysia.

A lateral flow rapid diagnostic test (RDT) enables detection of measles specific immunoglobulin M (IgM) antibody in serum, capillary blood, and oral fluid with accuracy consistent with enzyme immunoassay (EIA). The objectives of the study were: 1) to assess measles RDT inter-reader agreement between two clinic staff; 2) to assess the sensitivity and specificity of the measles RDT relative to standard surveillance testing in a low transmission setting; 3) to evaluate the knowledge, attitudes, and practices of staff in clinics using the RDT; and 4) to assess the impact of RDT testing on the measles public health response in Malaysia. The clinic-based prospective evaluation included all suspected measles cases captured by routine measles surveillance at 34 purposely selected clinics in 15 health districts in Malaysia between September 2019 and June 2020, following day-long regional trainings on RDT use. Following informed consent, four specimens were collected from each suspected case, including those routinely collected for standard surveillance [serum for EIA and throat swabs for quantitative reverse transcriptase polymerase chain reaction (RT-qPCR)] together with capillary blood and oral fluid tested with RDTs during the study. RDT impact was evaluated by comparing the rapidity of measles public health response between the pre-RDT implementation (December 2018 to August 2019) and RDT implementation periods (September 2019 to June 2020). To assess knowledge, attitudes, and practices of RDT use, staff involved in the public health management of measles at the selected sites were surveyed. Among the 436 suspect cases, agreement of direct visual readings of measles RDT devices between two health clinic staff was 99% for capillary blood (k = 0.94) and 97% for oral fluid (k = 0.90) specimens. Of the total, 45 (10%) were positive by measles IgM EIA (n = 44, including five also positive by RT-qPCR) or RT-qPCR only (n = 1), and 38 were positive by RDT (using either capillary blood or oral fluid). Using measles IgM EIA or RT-qPCR as reference, RDT sensitivity using capillary blood was 43% (95% CI: 30%-58%) and specificity was 98% (95% CI: 96%-99%); using oral fluid, sensitivity (26%, 95% CI: 15%-40%) and specificity (97%, 95% CI: 94%-98%) were lower. Nine months after training, RDT knowledge was high among staff involved with the public health management of measles (average quiz score of 80%) and was highest among those who received formal training (88%), followed by those trained during supervisory visits (83%). During the RDT implementation period, the number of days from case confirmation until initiation of public response decreased by about 5 days. The measles IgM RDT shows >95% inter-reader agreement, high retention of RDT knowledge, and a more rapid public health response. However, despite ≥95% RDT specificity using capillary blood or oral fluid, RDT sensitivity was <45%. Higher-powered studies using highly specific IgM assays and systematic RT-qPCR for case confirmation are needed to establish the role of RDT in measles elimination settings.

Epidemic characteristics of measles and efforts to control measles infections in Zhejiang Province, China.

Several countries have successfully eliminated measles, and China is making significant strides toward achieving this goal. This study focused on investigating the patterns of measles infections in Zhejiang Province, China, as well as control measures. The objective was to provide valuable insights that could contribute to the development of nationwide elimination strategies. We analyzed measles surveillance data from 2005 to 2022 in Zhejiang Province. We utilized a joinpoint regression model to examine trends in measles. Additionally, we employed SaTScan version 9.5 to identify spatial-temporal clusters. Finally, we used an age-period-cohort model to assess the effects of age, period, and cohort. The age-standardized incidence rate (ASIR) of measles infection in Zhejiang Province from 2005 to 2022 was 5.24 per 100,000, showing a consistent and significant downward trend with an annual percentage change of -24.93% (p<0.05). After 2020, the ASIR for measles infection fell to below 0.1 per 100,000. The majority of measles cases occurred in individuals either without an immunization history or with an unknown immunization status, representing 41.06% and 41.40% of the cases from 2010 to 2022, respectively. According to data from the National Measles Surveillance System, the annual rate of discarded measles cases from 2009 to 2014, and the annual rate of discarded measles and rubella cases from 2015 to 2022, were both above 2 per 100,000, indicating the high sensitivity of the measles surveillance system. The significant reduction in measles incidence from 2005 to 2022 demonstrates substantial progress in Zhejiang Province towards the elimination of measles.

Serological investigation of vaccine-induced antibodies for measles, rubella, and yellow fever viruses in children vertically exposed to Zika virus or with down syndrome.

Vaccination schedules, as well as their effectiveness and contraindications, need to be evaluated regularly, especially in specific situations. Congenital Zika Syndrome (CZS) is a severe condition that results in extensive functional and neurological impairment of fetuses and newborns due to Zika virus tropism for fetal neural progenitor cells. Down Syndrome (DS) is the leading genetic cause of intellectual disability. The immune impairment in DS has already been described, but little is known about the immune response of CZS children. Thus, CZS and DS are specific conditions that can be considered for a reassessment of the available immunizations. Here, we carried out serological analyses of attenuated vaccines-induced antibodies for measles, rubella, and yellow fever viruses in children aged 2-7, grouped into asymptomatic controls, DS children, and CZS children. Plasma samples were taken, and vaccination records were compiled during clinical follow-up. Enzymatic immunoassays for quantifying anti-measles and anti-rubella IgG were performed to assess the response to the Measles, Mumps, and Rubella (MMR) vaccine. Plaque Reduction Neutralization Test (PRNT) was performed to investigate neutralizing antibodies in response to the Brazilian vaccine strain of yellow fever (YF-17DD). We highlight similar levels of anti-measles IgG and neutralizing antibodies for YF-17DD among CZS, DS, and asymptomatic children, although low positivity of measles data was seen in the three groups. In DS children, the 2-4-year-old group had an increased level of anti-measles IgG compared to the older group of children aged five to seven years. Lower anti-rubella IgG levels were observed in CZS and DS children compared to asymptomatic children. For anti-rubella IgG, the good performance of vaccination in asymptomatic children is due to younger ones rather than older ones. There were no reports of adverse events after the use of the MMR and YF-17DD indicating that CZS and DS could continue to receive these vaccines, but our data draws attention to the necessity of monitoring the vaccination response in CZS and DS children over time and the possible need to adhere to national measles vaccination campaigns. Scientific research needs to continue to help develop appropriate CZS and DS health guidelines.

Genetic Characterization of the H Gene of MeV Strains (H1, B3, and D4) Recently Circulated in Iran for Improving the Molecular Measles Surveillance in the National Measles Lab.

Despite decreasing the global burden of measles disease after the introduction of vaccination, measles remains one of the most devastating childhood diseases. Since genotype B3 is reported as a predominant Measles Virus (MeV) genotype recently, the current study aimed to better understand MeV genetic variation by analyzing the complete sequence of Hemagglutinin (H) gene associated with outbreaks of circulated genotypes in Iran. Nine positive measles specimens were selected from three circulated different genotypes H1, B3, and D4. Two different regions of MeV RNA were detected by RT-PCR assay. Sequence data and phylogenetic trees were analyzed and constructed by MEGA X software program. Moreover, missense and silent mutations in critical positions of the MeV-H protein were investigated. The result of phylogenetic analysis from the C-terminus of the Nucleoprotein gene (NP-450) and the complete H gene revealed that the mean sequence diversity was 0.06%-0.08% and 0.04%, respectively. Genotype H1 had the highest mutation in this study; however, the substitutions in genotype B3 fundamentally occurred in critical epitopes. Moreover, genotype D4 was more stable than genotypes B3 and H1. Mutations were investigated in the whole sequence of H protein. Moreover, the mutations that occur in the critical sites of the protein have an important effect on the pathogenicity of the virus. In this way, we were able to illustrate why genotype B3 is more transmissible than other measles genotypes and is the most important circulating genotype around the world.

Molecular characterization of measles viruses in Central African Republic, 2012-2016.

Despite being preventable through vaccination, measles is still one of the most important causes of morbidity and mortality in young children in Africa. In 2015, several African countries, including the Central African Republic (CAR), began implementing national measles elimination programs. However, measles remains a public health problem in Africa, particularly in the CAR. A retrospective study was conducted at the Institut Pasteur de Bangui, using blood samples (n = 255) and oral swabs (n = 7) collected between January 2012 and December 2016 from measles IgM-positive cases, to attempt genotyping of circulating measles virus strains. Overall, 50 samples were positive by real-time polymerase chain reaction, and 40 sequences of acceptable quality were obtained. The phylogenetic analysis showed that 38 strains belonged to genotype B3 suggesting that this genotype was endemic in the CAR during the study period. No genotype B2 sequences were detected, suggesting that this genotype is no longer present in the CAR.

COMPARISON POTENCY ASSAY METHODS AS PLAQUE FORMING UNIT (PFU) AND CELL CULTURE INFECTIOUS DOSE 50% (CCID50) OF THE CANDIDATE NATIONAL REFERENCE STANDARD MEASLES VACCINE

A comparative study of two methods (PFU and CCID50) for potencydetermination for the national standard candidate measles vaccine was organized atthe National Institute for Control of Vaccines and Biologicals (NICVB). Twomethods are performed on the groups of candidate National Reference Standardmeasles vaccine derived from AIK-C strain stored at different temperatures: -700C,40C/7 days, 370C/7 days. The results show that although there is a difference, strongcorrelation exists between the two methods CCID50 and PFU with R2=0,886, r =0,94, coefficient PFU/CCID50 = 1.28 equivalent to the ratio PFU: CCID50 = 1:0.78.

Epidemiology of measles in Angola: Results from routine surveillance from 2015 to 2021

Measles, an acute infectious disease of extremely contagious viral aetiology, has been eliminated in some parts of the world. To the best of the authors' knowledge, this is the first study on the epidemiological pattern of the measles virus in Angola, and it was carried out through a review of 7 years of observational retrospective data from the national measles laboratory surveillance programme. A retrospective study using national databases on the laboratory surveillance of measles was performed. Patients of all ages with suspected measles from all provinces of Angola were included. Serum samples were used to detect IgM-type measles-virus-specific antibodies by enzyme-linked immunosorbent assay. In total, 3690 suspected measles samples were sent to the Instituto Nacional de Investigação em Saúde. There were 962 (26.1%) laboratory-confirmed cases, and the most affected age group was children aged 1-4 years. The highest incidence rate per 100,000 population was found in Benguela (17.9%), followed by Huambo (16.7%) and Cuanza Sul (13.6%). Of the study years, the incidence rate per 1,000,000 population was highest in 2020 (11.9%). The most common complication was diarrhoea (n=406, 42.2%). Of the confirmed cases, 209 (21.7%) were vaccinated, 633 (65.8%) were unvaccinated, and 120 (12.5%) had unknown vaccination status. For all study years, vaccination coverage was <70%. Measles continues to be a serious problem in Angola, and more efforts are needed to increase measles surveillance and achieve a high percentage of vaccination coverage.

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

In 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. We performed a cross-sectional study of measles cases in children under 18years, 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 12months and 6years). Children, under 18years, 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 12months (n=425) were excluded. Children aged 1-5years (n=785) and 6-17years (n=572) were expected to receive 1 and 2 measles vaccine doses, respectively. Most (88%) children (1-17years) were unvaccinated, 138 received 1 measles vaccine dose and 24 received 2 doses. Of children aged 1-5years 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. Data 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.

MMR vaccine coverage and associated factors among overseas-born refugee children resettled in Aotearoa New Zealand: a national retrospective cohort study

Refugee children may be under-immunised against common vaccine-preventable diseases due to a myriad of factors related to their migration journey. This retrospective cohort study explored the rates and determinants of enrolment on the National Immunisation Register (NIR) and measles, mumps and rubella (MMR) coverage among refugee children up to 18 years old who resettled in Aotearoa New Zealand (NZ) from 2006 to 2013. Univariate and multivariable logistic regression were conducted to determine associations. Of the cohort (N=2796), two thirds of the children (69%) were enrolled on the NIR. Among this sub-cohort (n=1926), less than one third (30%) were age-appropriately vaccinated with MMR. MMR coverage was highest among younger children and improved over time. Logistic modelling revealed that visa category, year of arrival, and age group were significant factors that influenced NIR enrolment and MMR vaccine uptake. Those arriving via asylum seeking, family reunification and humanitarian pathways were less likely to be enrolled and vaccinated compared to refugees who entered under the national quota programme. More recent arrivals and younger children were more likely to be enrolled and vaccinated compared to children who arrived in NZ longer ago and were older. Resettled refugee children have suboptimal NIR enrolment and MMR coverage rates which varied significantly by visa category, highlighting the need for immunisation services to better engage with all refugee families. These findings suggest that broad structural factors related to policy and immunisation service delivery may influence the differentials seen. Health Research Council of New Zealand (18/586).

Laboratory response to an infant with suspected measles vaccine associated fever and rash in Sri Lanka

BackgroundMeasles is a highly contagious illness. Sri Lanka (SL) has eliminated the measles in 2019. The country is at risk of importation of measles and there could be vaccine-associated measles like illnesses. Therefore, it is important to investigate patients with fever, rash to differentiate the wild-type from vaccine-type excluding other suspected pathogens to direct infection prevention and control strategies. The objective is to describe the laboratory investigation procedure in an immunocompetent child, developed fever, rash following measles containing vaccine in post-measles eliminated period, SL. MethodsThis laboratory based investigation was carried out in National Measles Laboratory, SL. Blood and throat swab were received from a patient with fever, rash, cough and coryza developed at tenth day of receiving the measles containing live-attenuated vaccine. Samples were tested for measles, rubella, and other relevant pathogens according to the laboratory testing algorithm for an immunocompetent child with fever, rash and flu like symptoms. ResultsMeasles vaccine type A, Edmonston-strain virus was detected after sequencing in throat swab and measles IgM and IgG were positive at sixth-week of illness-onset. In addition, influenza A RNA was detected in throat swab at day-three with detectable parvoB19 IgM in blood sample received at sixth-week of post-onset symptoms. ConclusionsMeasles like illness of this immunocompetent child who received measles containing vaccine could be due to measles vaccine-type A or influenza infection. In a measles eliminated, resource-limited setting in SL, there should be a well-defined, testing algorithm to exclude prevalent possible pathogens according to epidemiological and clinical information.

Epidemija morbila na teritoriji Smedereva

The Republic of Serbia is a country with endemic measles transmission. Decline of MMR immunization coverage resulted in measles resurgence in Serbia at the beginning of 2023. Aim of this study is a description of measles outbreak at the territory of the City of Smederevo between January and April 2023 and identification of interventions for prevention of future measles outbreaks in the Republic of Serbia. The national active measles surveillance data were analysed. The outbreak involved 43 measles cases, of whom 42 were classified as laboratory confirmed and one as epidemiologically linked. Most of cases were aged 1 to 4 years (44.2%) and 20 to 49 years (32.6%) while the highest age-specific incidence rates were registered in children younger than 12 months (80.6/10,000) and children aged 1 to 4 years (50.5/10,000). Most of cases with known vaccination status (92.9%) were unvaccinated including 8 children younger than 12 months not yet eligible for vaccination according to the national immunization schedule. Number of hospitalized cases were 20 (46.5%) including two cases with pneumonia. Among 14 cases who contracted measles in healthcare settings 5 were employees of General Hospital Smederevo. Genom sequencing was performed in 10 cases and B3 genotype of morbilli virus was detected in all cases. In order to prevent future measles outbreaks in the Republic of Serbia it is necessary to achieve and maintain target values of coverage and timeliness of MMR vaccination. Timely notification of suspected cases and diagnosis of measles as well as immunization of susceptible employees of healthcare institutions are key strategies for prevention of measles transmission in healthcare settings.

Molecular Epidemiological Study of Measles Cases in Gyeonggi Province

Measles is one of the highly contagious infectious diseases in which about 90% of the groups that have no immunity against measles are infected when exposed to the measles virus. Even after the Republic of Korea was certified as a ‘national measles eradication’ by the WHO in March 2014, two import-related outbreaks of measles occurred in 2014 and 2019. In this study, we analyzed epidemiological characteristics and genetic distribution of measles cases. Ninety-eight nasopharyngeal or oropharyngeal swab samples that confirmed cases of measles in Gyeonggi province in 2019 were conducted genotyping assay and sequence analysis. Fifty cases were classified as group outbreak-related cases and Forty-eight cases were classified as sporadic cases. As a result of genetic analysis, these cases were classified into D8, B3, and A genotypes, and except for the A type which was known as the vaccine type, D8 and B3 types were identified as import-related measles viruses. As with these results, for the complete eradication of measles, not only a high-quality surveillance system but also molecular epidemiological analysis data must be supported. The results of this study are expected to be used as important data for establishing a quarantine system through the accumulation of measles virus genotyping data and case reports data in the future when measles occurs in South Korea.

435. Investigation of the cause of low measles seroprevalence among young healthcare workers in South Korea

Abstract Background After a large measles outbreak in 2000∼2001, national measles vaccination program was implemented in Korea, and more than 95% of people born after 1985 have been vaccinated with 2-dose MMR. But sporadic outbreaks have continued to occur mainly in adults in their 20’s and 30’s in 2014 and 2019. Although low prevalence in young adults have been reported, there are limited data regarding the cause of low seropositivity (positive vaccine failure vs. secondary vaccine failure). We aimed to evaluate the cause of low seroprevalence of measles. Methods This study was performed in a 2743-bed tertiary-care hospital in South Korea. At 1-month after MMR vaccination in healthcare workers (HCWs) who were seronegative for measles, we performed measles antibody test(enzyme immunoassay), IgM/IgG index ratio, and avidity test. Results Of the 1,698 new HCWs in 2020 and, 1,686 in 2021, 54 HCWs with negative measles IgG at their entering at our hospital were enrolled in this study. Of these, 36(67%) were female, and the median age was 25 (IQR, 24-27) years. Of 43 HCWs who measured IgM/IgG index 1 month after MMR vaccination, 38 HCWs had IgM/IgG index of less than 1 and remaining 5 had negative IgG results (seroconversion rate of 88%). All 54 healthcare workers who performed avidity test showed high avidity index Measles vaccination record in KCDA showed that 45 had documented vaccination record during their childhood (of these, 11 received MMR vaccine again during their adult age) and remaining 9 had no documented vaccination record during their childhood. Of these 9 healthcare workers without record in their childhood, 3 had a history of vaccination at adult. Analyzing 48 healthcare workers with vaccination record, they received MMR vaccination median 18 years (IQR, 7-20) before. Therefore, at least 48 received at least 2 dose MMR vaccination, and 11 received at least 3 dose MMR vaccination. Conclusion Secondary vaccine failure may be the reason for vaccine failure in young adults in Korea. Therefore, HCWs with negative measles antibody who were born after 1985 may receive 1 dose booster vaccination rather than 2 dose vaccination. Disclosures All Authors: No reported disclosures.

Impact of disruptions to routine vaccination programs, quantifying burden of measles, and mapping targeted supplementary immunization activities

Measles is a highly transmissible disease that requires high levels of vaccination coverage for control and elimination. Areas that are unable to achieve and maintain high coverage levels are at risk for measles outbreaks resulting in increased morbidity and mortality. Public health emergencies, such as the current COVID-19 pandemic, pose a threat to the functioning of health systems by disrupting immunization services which can derail measles vaccination efforts. Efforts to bridge coverage gaps in immunization include the rapid return to fully functioning services as well as deploying supplementary immunization activities (SIAs), which are additional vaccination campaigns intended to catch-up children who have missed routine services. However, SIAs, which to date tend to be national efforts, can be difficult to mobilize quickly, resource-intensive, and even more challenging to deploy during a public health crisis. By mapping expected burden of measles, more effective SIAs that are setting-specific and resource-efficient can be planned and mobilized. Using a spatial transmission model of measles dynamics, we projected and estimated the expected burden of national and local measles outbreaks in Zambia with the current COVID-19 pandemic as a framework to inform disruptions to routine vaccination. We characterize the impact of disruptions to routine immunization services on measles incidence, map expected case burden, and explore SIA strategies to mitigate measles outbreaks. We find that disruptions lasting six months or longer as well as having low MCV1 coverage prior to disruptions resulted in an observable increase of measles cases across provinces. Targeting provinces at higher risk of measles outbreaks for SIAs is an effective strategy to curb measles virus incidence following disruptions to routine immunization services.

A study on relationship between the incidence of measles and nosocomial exposure at measles epidemic season in Chongqing.

After measles vaccine supplementary immunization, the epidemiological characteristics of measles have changed in Chongqing, China. In addition, according to data from the National Measles Surveillance Information System, the proportion of measles cases with a history of hospital visit 7 to 21 days prior to onset of measles increased year by year to 32.1% in 2016. Further studies are necessary to eliminate the influence of nosocomial exposure on measles. We performed a case-control study in seven districts of Chongqing from June to August 2016 to identify risk factors for measles virus infection and susceptibility. Laboratory-confirmed measles who younger than 5 years old were matched with one control by age and residence. We interviewed case patients and controls regarding potential risk factors for measles virus infection and susceptibility. Unadjusted and adjusted matched odds ratios and 95% confidence intervals (CIs) were calculated using non-conditional logistic regression. After a cross-sectional analysis of the behavioral characteristics of visiting hospitals in the case and control groups, it was found that there was a difference between the two groups in the choice of hospitals visited for the first time (χ2 = 35.500, P = .000), and that nosocomial transmission risk tended to develop in outpatient services of respiratory medicine. After analysis using one-way ANOVA, the relationship between hospital visits prior to onset and the incidence risk of measles was that visiting hospitals five times within 1 to 3 weeks prior to onset affected the incidence (OR = 44.866, 95%CI = 5.938–338.981). The relationship between the number of types of hospitals visited prior to onset and the risk of nosocomial exposure to measles showed that visiting any community hospital, children’s hospital, or general hospital had no risk, but visiting two or more of these hospitals affected the incidence (OR = 6.928, 95%CI = 3.849–13.754). Based on further analysis, the relationship between the number of hospital visits after onset and the risk of nosocomial exposure to measles was that the chances of visiting hospitals increased after onset. Risks of nosocomial exposure to measles and infections are high in pediatric hospitals. Nosocomial exposure risk factors should be considered when controlling measles.