A review of testing used in seroprevalence studies on measles and rubella

Serosurveillance for Measles and Rubella

Measles and rubella remain global health threats, despite the availability of safe and effective vaccines. Estimates of population immunity are crucial for achieving elimination goals and assessing the impact of vaccination programs, yet conducting well-designed serosurveys can be challenging, especially in resource-limited settings. In this review, we provide a comprehensive assessment of 130 measles and rubella studies published from January 2014 to January 2024. Methodologies and design aspects of serosurveys varied greatly, including sample size, assay type, and population demographics. Most studies utilized enzyme immunoassays for IgG detection. Sample sizes showed diverse sampling methods but favored convenience sampling despite its limitations. Studies spanned 59 countries, predominantly including adults, and revealed disparities in seroprevalence across demographics, regions, and notably among migrants and women. Age-related declines in antibodies were observed, particularly among infants, and correlations between vaccination status and seropositivity varied. We conclude with an outlook on measles and rubella serosurveillance, emphasizing the need for proper survey design and the advantages of standardized, multiplex serology assays.

Immunity of Canadians and risk of epidemics workshop - Conference report

On November 18-19, 2019, the Immunity of Canadians and Risk of Epidemics (iCARE) Network convened a workshop in Toronto, Ontario, Canada. The objectives of the workshop were to raise the profile of sero-epidemiology in Canada, discuss best practice and methodological innovations, and strategize on the future direction of sero-epidemiology work in Canada. In this conference report, we describe the presentations and discussions from the workshop, and comment on the impact of the COVID-19 pandemic on serosurveillance initiatives, both in Canada and abroad.

Updates on Measles Incidence and Eradication: Emphasis on the Immunological Aspects of Measles Infection

Measles is an RNA virus infectious disease mainly seen in children. Despite the availability of an effective vaccine against measles, it remains a health issue in children. Although it is a self-limiting disease, it becomes severe in undernourished and immune-compromised individuals. Measles infection is associated with secondary infections by opportunistic bacteria due to the immunosuppressive effects of the measles virus. Recent reports highlight that measles infection erases the already existing immune memory of various pathogens. This review covers the incidence, pathogenesis, measles variants, clinical presentations, secondary infections, elimination of measles virus on a global scale, and especially the immune responses related to measles infection.

Design of a chimaeric antigen and its use in the detection of IgG antibodies against rubella virus

BACKGROUND

Rubella virus (RV) is the causative agent of rubella or German measles. Although most infections cause only mild self-limited measles-like illness, the infection in pregnant women can cause severe foetal malformation or even miscarriage, especially in the first 3 months of pregnancy. Therefore, it is of great practical significance to establish a simple and sensitive RV detection method.

METHODS

The partial epitopes of the E1 and E2 proteins from Rubella Virus were selected as the target sites, the sequence of the selected antigenic sites of the E1 and E2 were linked by a linker. The expression plasmid P6T was constructed by inserting the gene into PET-32A + with a histidine Tag. The P6 protein was induced and expressed in Escherichia coli L21 (DE3) and purified by nickel column affinity. The protein P6 antigen was identified by Western blotting analysis, and an anti-P6 antibody ELISA was established to test known serum samples to evaluate the capability of this method.

RESULTS

After purification, the concentration and purity of the protein P6 were 0.283 mg/mL and more than 80%, respectively. Western blotting analysis showed that the protein P6 could react with rubella virus positive serum. By ELISA, 36 negative sera and 58 positive sera were detected. The coincidence rate, specificity and sensitivity of the ELISA were 86.2%, 88.89% and 84.48%, respectively. The P6 ELISA with a kappa coefficient of 0.715, P < 0.05, indicated excellent consistency.

CONCLUSIONS

The protein P6 with excellent antigenicity obtained from prokaryotic expression followed by chromatography purification could prove useful for early diagnosis of RV infection.

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.

Evaluation of Dried Blood Spot Testing for SARS-CoV-2 Serology Using a Quantitative Commercial Assay

Dried blood spots (DBS) are commonly used for serologic testing for viruses and provide an alternative collection method when phlebotomy and/or conventional laboratory testing are not readily available. DBS collection could be used to facilitate widespread testing for SARS-CoV-2 antibodies to document past infection, vaccination, and potentially immunity. We investigated the characteristics of Roche's Anti-SARS-CoV-2 (S) assay, a quantitative commercial assay for antibodies against the spike glycoprotein. Antibody levels were reduced relative to plasma following elution from DBS. Quantitative results from DBS samples were highly correlated with values from plasma (r2 = 0.98), allowing for extrapolation using DBS results to accurately estimate plasma antibody levels. High concordance between plasma and fingerpick DBS was observed in PCR-confirmed COVID-19 patients tested 90 days or more after the diagnosis (45/46 matched; 1/46 mismatched plasma vs. DBS). The assessment of antibody responses to SARS-CoV-2 using DBS may be feasible using a quantitative anti-S assay, although false negatives may rarely occur in those with very low antibody levels.

Development of a Measles and Rubella Multiplex Bead Serological Assay for Assessing Population Immunity

Serosurveys are important tools for estimating population immunity and providing immunization activity guidance. The measles and rubella multiplex bead assay (MBA) offers multiple advantages over standard serological assays and was validated by comparison with the enzyme-linked immunosorbent assay (ELISA) and the measles plaque reduction neutralization (PRN) assay. Results from a laboratory-produced purified measles virus whole-virus antigen MBA (MeV WVAL) correlated better with ELISA and PRN than results from the baculovirus-expressed measles nucleoprotein (N) MBA. Therefore, a commercially produced whole-virus antigen (MeV WVAC) was evaluated. Serum IgG antibody concentrations correlated significantly with a strong linear relationship between the MeV WVAC and MeV WVAL MBAs (R = 0.962 and R2 = 0.926). IgG concentrations from the MeV WVAC MBA showed strong correlation with PRN titers (R = 0.846), with a linear relationship comparable to values obtained with the MeV WVAL MBA and PRN assay (R2 = 0.716 and R2 = 0.768, respectively). Receiver operating characteristic (ROC) curve analysis of the MeV WVAC using PRN titer as the comparator resulted in a seroprotection cutoff of 153 mIU/ml, similar to the established correlate of protection of 120 mIU/ml, with a sensitivity of 98% and a specificity of 83%. IgG concentrations correlated strongly between the rubella WVA MBA and ELISA (R = 0.959 and R2 = 0.919). ROC analysis of the rubella MBA using ELISA as the comparator yielded a cutoff of 9.36 IU/ml, similar to the accepted cutoff of 10 IU/ml for seroprotection, with a sensitivity of 99% and a specificity of 100%. These results support use of the MBA for multiantigen serosurveys assessing measles and rubella population immunity.

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

BACKGROUND

In 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.

METHODS

A 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.

RESULTS

Among 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.

CONCLUSIONS

Nationally, 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.

Non-invasive detection of IgG antibodies from common pathogenic viruses using oral flocked swabs

Salivary antibodies are useful in surveillance and vaccination studies. However, low antibody levels and degradation by endonucleases are problematic. Oral flocked swabs are a potential non-invasive alternative for detecting viral antibodies. Seroprevalence for Cytomegalovirus (CMV), Varicella-Zoster virus (VZV), Epstein-Barr virus (EBV), Measles and Mumps IgG antibodies were determined from 50 matched serum, saliva and swabs samples from healthy volunteers using commercial ELISAs. CMV IgG, VZV IgG, and EBV EBNA-1 IgG, VCA IgG, and Measles IgG swab versus serum sensitivities were 95.8%, 96.0%, 92.1%, 95.5%, 84.5%, respectively, and swabs correlated well with saliva. Sensitivity of Mumps IgG in swabs and saliva was poor at 60.5%, and 68.2%, respectively. Specificities for IgG antibodies were 100% for CMV, EBV and Mumps, but could not be determined for VZV and Measles due to exclusively seropositive volunteers. Except for Mumps IgG, swabs correlate well with serum, are easy to self-collect and are stable at room temperature.

Recent trends in seroprevalence of rubella in Korean women of childbearing age: a cross-sectional study

OBJECTIVES

The aim of this study was to investigate the immunity against rubella using the serological status of rubella-specific IgG antibodies (antirubella IgG) in Korean women of childbearing age (15-49 years).

DESIGN

Retrospective cross-sectional study.

SETTING

Population-based cross-sectional study in South Korea.

PARTICIPANTS

Between January 2010 and December 2017, test results from Korean women aged 15-49 years who had visited an obstetric private clinic (nationwide institutions) and had requested rubella-specific IgG antibody tests from Green Cross Laboratories were obtained from the laboratory information system.

RESULTS

Between 2010 and 2017, antirubella IgG test results from 328 426 Korean women aged 15-49 years who had visited private obstetric clinics (1438 institutions nationwide) were retrospectively analysed by tested year, age, cohort and geographic regions. Over the 8-year study period, the rate of unimmunised women ranged from 7.8% to 9.7%. Multivariable-adjusted logistic regression models showed that the odds of being immune to rubella (positive and equivocal results of antirubella IgG test) were lower in 2017 compared with 2010, in women in their 40s, in a pre-catch-up cohort and in women living in Incheon, Busan, South Gyeongsang, North and South Jeolla and Jeju provinces (p<0.0001).

CONCLUSIONS

In consideration of the factors associated with prevalence of women unimmunised to rubella, future public health efforts should be focused on catch-up activities. The results of this study could be used to strengthen disease control and prevent rubella, including a nationwide immunisation programme.

Measles and rubella seroimmunity in newly arrived adult immigrants in Sweden

BACKGROUND

International migrants could be considered as a risk group for being susceptible to vaccine preventable diseases such as measles and rubella. However, data on immunity in different migrant groups are scarce. Apart from asylum seekers and refugees, other immigrant groups might also be at risk. We have examined measles and rubella specific IgG antibodies among newly arrived adult immigrants in Skåne region in southern Sweden. In contrast to children, adult immigrants are not offered catch-up vaccinations after arrival.

METHODS

Stored serum samples from 989 asylum seekers and 984 pregnant women from the antenatal screening program, who had recently settled in Sweden, were analyzed for specific measles and rubella IgG-antibodies. Sex, age, reason for screening and geographic origin were variables entered into a multivariate regression model.

RESULTS

There were considerable differences in seroimmunity to measles with regard to geographic origin (44-97%). Measles seroimmunity gaps were most prominent in immigrants from some European regions such as the Baltic countries, the former Yugoslavia and the Newly Independent States and Russia. Seroprotection for rubella varied less between geographic regions (90-99%).

CONCLUSION

Susceptibility to measles among adult immigrants arriving in Sweden varies considerably depending on their geographic origin. Vaccinations against measles and rubella should be offered to groups of immigrants who might be incompletely immunized.

Current perspectives in assessing humoral immunity after measles vaccination

INTRODUCTION

Repeated measles outbreaks in countries with relatively high vaccine coverage are mainly due to failure to vaccinate and importation; however, cases in immunized individuals exist raising questions about suboptimal measles vaccine-induced humoral immunity and/or waning immunity in a low measles-exposure environment.

AREAS COVERED

The plaque reduction neutralization measurement of functional measles-specific antibodies correlates with protection is the gold standard in measles serology, but it does not assess cellular-immune or other parameters that may be associated with durable and/or protective immunity after vaccination. Additional correlates of protection and long-term immunity and new determinants/signatures of vaccine responsiveness such as specific CD46 and IFI44L genetic variants associated with neutralizing antibody titers after measles vaccination are under investigation. Current and future systems biology studies, coupled with new technology/assays and analytical approaches, will lead to an increasingly sophisticated understanding of measles vaccine-induced humoral immunity and will identify 'signatures' of protective and durable immune responses.

EXPERT OPINION

This will translate into the development of highly predictive assays of measles vaccine efficacy, effectiveness, and durability for prospective identification of potential low/non-responders and susceptible individuals who require additional vaccine doses. Such new advances may drive insights into the development of new/improved vaccine formulations and delivery systems.

Public health responses during measles outbreaks in elimination settings: Strategies and challenges

In late September 2016, the Americas became the first region in the world to have eliminated endemic transmission of measles virus. Several other countries have also verified measles elimination, and countries in all six World Health Organization regions have adopted measles elimination goals. The public health strategies used to respond to measles outbreaks in elimination settings are thus becoming relevant to more countries. This review highlights the strategies used to limit measles spread in elimination settings: (1) assembly of an outbreak control committee; (2) isolation of measles cases while infectious; (3) exclusion and quarantining of individuals without evidence of immunity; (4) vaccination of susceptible individuals; (5) use of immunoglobulin to prevent measles in exposed susceptible high-risk persons; (6) and maintaining laboratory proficiency for confirmation of measles. Deciding on the extent of containment efforts should be based on the expected benefit of reactive interventions, balanced against the logistical challenges in implementing them.

Benefits and Challenges in Using Seroprevalence Data to Inform Models for Measles and Rubella Elimination

Background

Control efforts for measles and rubella are intensifying globally. It becomes increasingly important to identify and reach remaining susceptible populations as elimination is approached.

Methods

Serological surveys for measles and rubella can potentially measure susceptibility directly, but their use remains rare. In this study, using simulations, we outline key subtleties in interpretation associated with the dynamic context of age-specific immunity, highlighting how the patterns of immunity predicted from disease surveillance and vaccination coverage data may be misleading.

Results

High-quality representative serosurveys could provide a more accurate assessment of immunity if challenges of conducting, analyzing, and interpreting them are overcome. We frame the core disease control and elimination questions that could be addressed by improved serological tools, discussing challenges and suggesting approaches to increase the feasibility and sustainability of the tool.

Conclusions

Accounting for the dynamical context, serosurveys could play a key role in efforts to achieve and sustain elimination.

Characterization of rubella-specific humoral immunity following two doses of MMR vaccine using proteome microarray technology

Introduction//Background

The lack of standardization of the currently used commercial anti-rubella IgG antibody assays leads to frequent misinterpretation of results for samples with low/equivocal antibody concentration. The use of alternative approaches in rubella serology could add new information leading to a fuller understanding of rubella protective immunity and neutralizing antibody response after vaccination.

Methods

We applied microarray technology to measure antibodies to all rubella virus proteins in 75 high and 75 low rubella virus-specific antibody responders after two MMR vaccine doses. These data were used in multivariate penalized logistic regression modeling of rubella-specific neutralizing antibody response after vaccination.

Results

We measured antibodies to all rubella virus structural proteins (i.e., the glycoproteins E1 and E2 and the capsid C protein) and to the non-structural protein P150. Antibody levels to each of these proteins were: correlated with the neutralizing antibody titer (p<0.006); demonstrated differences between the high and the low antibody responder groups (p<0.008); and were components of the model associated with/predictive of vaccine-induced rubella virus-specific neutralizing antibody titers (misclassification error = 0.2).

Conclusion

Our study supports the use of this new technology, as well as the use of antibody profiles/patterns (rather than single antibody measures) as biomarkers of neutralizing antibody response and correlates of protective immunity in rubella virus serology.