Validation of an anti-measles virus-specific IgG assay with oral fluid samples for immunization surveillance in Bangladesh

Adjustments for oral fluid quality and collection methods improve prediction of circulating tetanus antitoxin: Approaches for correcting antibody concentrations detected in a non-invasive specimen

OBJECTIVES

To examine whether anti-tetanus toxoid (anti-TT) immunoglobulin G (IgG) levels measured in oral fluid and adjusted for collection difficulties and specimen quality are associated with total IgG and anti-TTIgG in oral fluid and assess if statistical adjustment for them improves prediction of anti-TT IgG in serum.

METHODS

267 children, ages 12 to 15 months, enrolled in the M-SIMU randomized controlled trial participated in this nested cross-sectional analysis. Venous blood and oral fluid (OF) specimens were collected, and OF collection difficulties such as crying or gagging were recorded. OF volume was documented and total IgG was measured in OF specimens and anti-TT IgG was measured in OF and serum by enzyme immunoassay (EIA). Collection difficulties, volume and sociodemographic characteristics were assessed in relation to total IgG and anti-TT IgG in OF via multivariate regression. These models were extended to evaluate the association between anti-TT IgG in OF and in serum. A prediction model was developed to adjust anti-TT IgG in OF estimates as proxy for serum.

RESULTS

Blood in the specimen, sores in the mouth and crying were positively associated with total IgG concentration while high oral fluid volume and sucking on the swab were inversely associated. None were significant predictors of anti-TT IgG in OF after adjusting for total IgG (geometric mean [GM] ratio: 1.99; 95% confidence interval: 1.78-2.24) and vaccination history (GM ratio: 2.44; 95% CI: 1.98-3.01). When predicting anti-TT IgG levels in serum with OF, total IgG modified the effect of anti-TT IgG in OF.

CONCLUSIONS

Anti-TT IgG in OF is a good proxy for levels in serum, after controlling for total IgG in the specimen and other variables. Post hoc adjustments for OF volume and total IgG concentration are an important consideration when conducting serosurveys with oral fluid.

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.

Serological Surveys for complementing assessments of vaccination coverage in sub-Saharan Africa: A systematic review

Background: Serosurveys of biomarkers of infection/vaccination are widely used for evaluating vaccine-induced immunity and monitoring the effectiveness of immunisation programmes in developed countries. In sub-Saharan Africa (sSA) where vaccination coverage (VC) estimates are often incomplete, inaccurate and overestimate effective population immunity, the use of serosurveys is limited. Methods: We conducted a review of the use of serosurveys to assess/complement assessments of VC in sSA by searching electronic databases (PubMed, Embase, Web of Science, Popline, Ovid and Africa Wide Information) for English language articles published from 1st January 1940 to 31st January 2017. We also searched the references of retrieved articles. SSA was defined as all of Africa excluding the countries in North Africa. We included only articles that measured VC and assessed the quality of these studies using the Newcastle-Ottawa Scale. Results: We found 1056 unique records, reviewed 20 eligible studies of which just 12 met our inclusion criteria. These 12 studies were serosurveys of measles, tetanus, polio and yellow fever. Antibodies induced by natural infection confounded serological test results and there was significant discordance between vaccination history and the presence of antibodies in all except for tetanus vaccine. No study looked at Hepatitis B. Conclusions: Serosurveys for tetanus or tetanus containing vaccines may be directly useful for ascertainment of vaccination exposure or reliably complement current survey methods that measure VC. Given the limited experience in using serosurveys for this purpose in sSA, well-designed serosurveys of tetanus and possibly hepatitis B are required to further validate/evaluate their performance.

IgG antibody prevalence suggests high immunization needs in newcomers to Luxembourg, 2012

Vaccine coverage of the general population in Luxembourg is high, but refugees or asylum seekers may be incompletely vaccinated and susceptible to vaccine-preventable diseases. In order to assess protection rates, serum and oral fluid samples were collected from 406 newcomers aged between 13 and 70 years arriving between May and September 2012. Sera were screened for IgG antibodies against measles, rubella, mumps, hepatitis B, tetanus, diphtheria and pertussis. Oral fluid samples were screened for antibodies against measles, mumps and rubella virus to investigate their suitability for antibody prevalence studies. More than 90% of the participants had IgG antibodies against rubella, 73% against measles and 56% against mumps. Less than 19% had anti-HBs antibodies. Nearly 84% of the participants had an adequate protection against tetanus, 73% against diphtheria and 40% had pertussis antibodies. 93%, 95% and 78% of the measles, rubella and mumps test results obtained with serum and oral fluid were concordant. The majority of the participants lacked antibodies against at least one of the measles/mumps/rubella (58%) and diphtheria/tetanus/pertussis (72%) vaccine components and against hepatitis B virus (82%) and might thus profit from vaccination. Oral fluid is a suitable alternative and non-invasive specimen for measles/rubella antibody prevalence studies.

Measles

Measles is a highly contagious disease that results from infection with measles virus and is still responsible for more than 100 000 deaths every year, down from more than 2 million deaths annually before the introduction and widespread use of measles vaccine. Measles virus is transmitted by the respiratory route and illness begins with fever, cough, coryza, and conjunctivitis followed by a characteristic rash. Complications of measles affect most organ systems, with pneumonia accounting for most measles-associated morbidity and mortality. The management of patients with measles includes provision of vitamin A. Measles is best prevented through vaccination, and the major reductions in measles incidence and mortality have renewed interest in regional elimination and global eradication. However, urgent efforts are needed to increase stagnating global coverage with two doses of measles vaccine through advocacy, education, and the strengthening of routine immunisation systems. Use of combined measles-rubella vaccines provides an opportunity to eliminate rubella and congenital rubella syndrome. Ongoing research efforts, including the development of point-of-care diagnostics and microneedle patches, will facilitate progress towards measles elimination and eradication.

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

Seroprevalence studies are an essential tool to monitor the efficacy of vaccination programmes, to understand population immunity and to identify populations at higher risk of infection. An overarching review of all aspects of seroprevalence studies for measles and rubella published between 1998 and June 2014 was undertaken and the findings reported elsewhere. This paper details the considerable variation in the testing formats identified in the review. Apart from serum/plasma samples, testing of oral fluid, breast milk, dry blood spots and capillary whole blood were reported. Numerous different commercial assays were employed, including microtitre plate assays, automated immunoassays and classical haemagglutination inhibition and neutralisation assays. A total of 29 of the 68 (43%) measles and 14 of the 58 (24%) rubella studies reported qualitative test results. Very little information on the testing environment, including quality assurance mechanisms used, was provided. Due to the large numbers of testing systems, the diversity of sample types used and the difficulties in accurate quantification of antibody levels, the results reported in individual studies were not necessarily comparable. Further efforts to standardise seroprevalence studies may overcome this deficiency.

Issues and considerations in the use of serologic biomarkers for classifying vaccination history in household surveys

Accurate estimates of vaccination coverage are crucial for assessing routine immunization program performance. Community based household surveys are frequently used to assess coverage within a country. In household surveys to assess routine immunization coverage, a child's vaccination history is classified on the basis of observation of the immunization card, parental recall of receipt of vaccination, or both; each of these methods has been shown to commonly be inaccurate. The use of serologic data as a biomarker of vaccination history is a potential additional approach to improve accuracy in classifying vaccination history. However, potential challenges, including the accuracy of serologic methods in classifying vaccination history, varying vaccine types and dosing schedules, and logistical and financial implications must be considered. We provide historic and scientific context for the potential use of serologic data to assess vaccination history and discuss in detail key areas of importance for consideration in the context of using serologic data for classifying vaccination history in household surveys. Further studies are needed to directly evaluate the performance of serologic data compared with use of immunization cards or parental recall for classification of vaccination history in household surveys, as well assess the impact of age at the time of sample collection on serologic titers, the predictive value of serology to identify a fully vaccinated child for multi-dose vaccines, and the cost impact and logistical issues on outcomes associated with different types of biological samples for serologic testing.

Measles vaccination coverage estimates from surveys, clinic records, and immune markers in oral fluid and blood: a population-based cross-sectional study

Background

Recent outbreaks of measles and polio in low-income countries illustrate that conventional methods for estimating vaccination coverage do not adequately identify susceptible children. Immune markers of protection against vaccine-preventable diseases in oral fluid (OF) or blood may generate more accurate measures of effective vaccination history, but questions remain about whether antibody surveys are feasible and informative tools for monitoring immunization program performance compared to conventional vaccination coverage indicators. This study compares six indicators of measles vaccination status, including immune markers in oral fluid and blood, from children in rural Bangladesh and evaluates the implications of using each indicator to estimate measles vaccination coverage.

Methods

A cross-sectional population-based study of children ages 12–16 months in Mirzapur, Bangladesh, ascertained measles vaccination (MCV1) history from conventional indicators: maternal report, vaccination card records, ‘card + history’ and EPI clinic records. Oral fluid from all participants (n = 1226) and blood from a subset (n = 342) were tested for measles IgG antibodies as indicators of MCV1 history and compared to conventional MCV1 coverage indicators.

Results

Maternal report yielded the highest MCV1 coverage estimates (90.8%), followed by EPI records (88.6%), and card + history (84.2%). Seroprotection against measles by OF (57.3%) was significantly lower than other indicators, even after adjusting for incomplete seroconversion and assay performance (71.5%). Among children with blood results, 88.6% were seroprotected, which was significantly higher than coverage by card + history and OF serostatus but consistent with coverage by maternal report and EPI records. Children with vaccination cards or EPI records were more likely to have a history of receiving MCV1 than those without cards or records. Despite similar MCV1 coverage estimates across most indicators, within-child agreement was poor for all indicators.

Conclusions

Measles IgG antibodies in OF was not a suitable immune marker for monitoring measles vaccination coverage in this setting. Because agreement between conventional MCV1 indicators was mediocre, immune marker surveillance with blood samples could be used to validate conventional MCV1 indicators and generate adjusted results that can be compared across indicators.