Performance Evaluation of the VIDAS(®) Measles IgG Assay and Its Diagnostic Value for Measuring IgG Antibody Avidity in Measles Virus Infection

The objective of this study is primarily to compare the performance of the VIDAS(®) Measles immunoglobulin (Ig)G assay to that of two other serological assays using an immunoassay technique, Enzygnost(®) Anti-measles Virus/IgG (Siemens) and Measles IgG CAPTURE EIA(®) (Microimmune). The sensitivity and the agreement of the VIDAS(®) Measles IgG assay compared to the Enzygnost(®) Anti-measles Virus/IgG assay and the Measles IgG CAPTURE EIA(®) assay are 100%, 97.2% and 99.0%, 98.4%, respectively. The very low number of negative sera for IgG antibodies does not allow calculation of specificity. As a secondary objective, we have evaluated the ability of the VIDAS(®) Measles IgG assay to measure anti-measles virus IgG antibody avidity with the help of the VIDAS(®) CMV IgG Avidity reagent, using 76 sera from subjects with measles and 238 other sera. Different groups of populations were analyzed. In the primary infection measles group, the mean IgG avidity index was 0.16 (range of 0.07 to 0.93) compared to 0.79 (range of 0.25 to 1) in the serum group positive for IgG antibodies and negative for IgM. These data allow to define a weak anti-measles virus IgG antibody avidity as an avidity index (AI) < 0.3 and a strong avidity as an AI > 0.6. The VIDAS(®) Measles IgG assay has a performance equivalent to that of other available products. Its use, individual and quick, is well adapted to testing for anti-measles immunity in exposed subjects.

[An update on measles]

Measles is a highly contagious infectious disease, which needs more than 95% worldwide vaccination coverage of 2 doses to be eradicated. Despite an important involvement of the WHO for massive immunization, goals have not bean reached, and outbreaks can occur at any time in many countries, including Western Europe. In France, 22,000 cases were identified between 2009 and 2011, mainly in infants and young adults, which are not or not enough vaccinated (one dose). In 2012, even though the number of cases has drastically decreased, the outbreak is still going on, especially in South of France. That is why every clinician needs to be concerned about the clinical manifestations of the disease, and its complications. Besides a febrile rash, measles is often responsible of pneumonia and biologic hepatitis in adults. Hepatitis does not seem frequent in children. Clinicians need to be aware of specific complications, like encephalitis in case of cellular immunodepression, high risk of pneumonia in pregnant women. In patients previously vaccinated, incidence of complications is the same but patients are not contagious. Even if measles diagnosis is clinical, blood confirmation by serology is recommended in France when possible. Outcome is mainly favourable, but measles is not well-tolerated with high levels of hospitalisation even without any complication. Vaccination is the only way to protect against it.

Laboratory characterization of measles virus infection in previously vaccinated and unvaccinated individuals

Waning immunity or secondary vaccine failure (SVF) has been anticipated by some as a challenge to global measles elimination efforts. Although such cases are infrequent, measles virus (MeV) infection can occur in vaccinated individuals following intense and/or prolonged exposure to an infected individual and may present as a modified illness that is unrecognizable as measles outside of the context of a measles outbreak. The immunoglobulin M response in previously vaccinated individuals may be nominal or fleeting, and viral replication may be limited. As global elimination proceeds, additional methods for confirming modified measles cases may be needed to understand whether SVF cases contribute to continued measles virus (MeV) transmission. In this report, we describe clinical symptoms and laboratory results for unvaccinated individuals with acute measles and individuals with SVF identified during MeV outbreaks. SVF cases were characterized by the serological parameters of high-avidity antibodies and distinctively high levels of neutralizing antibody. These parameters may represent useful biomarkers for classification of SVF cases that previously could not be confirmed as such using routine laboratory diagnostic techniques.

[Measles in the Nantes Teaching Hospital during the 2008-2009 epidemic]

OBJECTIVE

A recent measles epidemic in France incited us to report and describe measles cases requiring hospitalization, to raise the awareness of health professionals on under-diagnosis and frequent complications of this viral disease.

DESIGN

We carried out a retrospective and epidemiologic study of measles cases recorded in the Nantes Teaching Hospital between August 2008 and September 2009. All these cases where confirmed by biological diagnosis and recorded by the Teaching Hospital virological laboratory.

RESULTS

Thirteen cases of measles (11 adults and two children) were recorded during the study period. Adults were young (mean age 21.4 years); the oldest was 35 years old. We noted two severe cases with viral pneumonia and hypoxemia and one case with bacterial pneumonia. Two female patients were pregnant; one delivered prematurely, in the acute phase of measles, with no complication for the newborn. Two cases occurred in the nursing staff by documented nosocomial transmission. Sixty-nine percent of the patients were not vaccinated whereas the vaccinal status was not documented for 31%.

CONCLUSIONS

These cases underline the potential severity of this infection and the difficulty to diagnose measles at the early phase because of lack of awareness of medical staff. It will be necessary to reinforce prevention messages and promote measles vaccination in children as well as in young people and health workers.

[Measles in adults: an emerging disease not sparing medical staff]

BACKGROUND

A large outbreak of measles is taking place in Europe and is related to a low vaccination coverage. Measles is observed in adults.

METHODS

We retrospectively studied all the consecutive cases of measles seen in adults between the 1/1/2007 and the 30/4/2009 in four Parisian hospitals.

RESULTS

Twenty-one patients were included. Six patients (29%) were health care workers (HCW) including five (83%) who were vaccinated. Twenty (95%) patients were hospitalized. All patients presented with febrile exanthema, cough and rhinitis in association with hepatic involvement in 71%. Neither death nor sequelae were reported.

CONCLUSION

Measles may occur in HCW, most of them being insufficiently covered by the vaccination. Therefore, since 2010, one injection of measles vaccine is now recommended in France, for HCW without history of measles or vaccination with two doses. Furthermore, adequate respiratory precautions should be taken when seeing patients with febrile exanthema and cough.

Evaluating measles surveillance: comparison of sentinel surveillance, mandatory notification, and data from health insurance claims

Inadequate notification is a recognized problem of measles surveillance systems in many countries, and it should be monitored using multiple data sources. We compared data from three different surveillance sources in 2007: (1) the sentinel surveillance system mandated by the Act on Prevention of Infectious Diseases and Medical Care for Patients Suffering Infectious Diseases, (2) the mandatory notification system run by the Aichi prefectural government, and (3) health insurance claims (HICs) submitted to corporate health insurance societies. For each dataset, we examined the number of measles cases by month, within multiple age groups, and in two categories of diagnostic test groups. We found that the sentinel surveillance system underestimated the number of adult measles cases. We also found that HIC data, rather than mandatory notification data, were more likely to come from individuals who had undergone laboratory tests to confirm their measles diagnosis. Thus, HIC data may provide a supplementary and readily available measles surveillance data source.

Measles outbreak in a highly vaccinated population, San Diego, 2008: role of the intentionally undervaccinated

OBJECTIVE

In January 2008, an intentionally unvaccinated 7-year-old boy who was unknowingly infected with measles returned from Switzerland, resulting in the largest outbreak in San Diego, California, since 1991. We investigated the outbreak with the objective of understanding the effect of intentional undervaccination on measles transmission and its potential threat to measles elimination.

METHODS

We mapped vaccination-refusal rates according to school and school district, analyzed measles-transmission patterns, used discussion groups and network surveys to examine beliefs of parents who decline vaccination, and evaluated containment costs.

RESULTS

The importation resulted in 839 exposed persons, 11 additional cases (all in unvaccinated children), and the hospitalization of an infant too young to be vaccinated. Two-dose vaccination coverage of 95%, absence of vaccine failure, and a vigorous outbreak response halted spread beyond the third generation, at a net public-sector cost of $10 376 per case. Although 75% of the cases were of persons who were intentionally unvaccinated, 48 children too young to be vaccinated were quarantined, at an average family cost of $775 per child. Substantial rates of intentional undervaccination occurred in public charter and private schools, as well as public schools in upper-socioeconomic areas. Vaccine refusal clustered geographically and the overall rate seemed to be rising. In discussion groups and survey responses, the majority of parents who declined vaccination for their children were concerned with vaccine adverse events.

CONCLUSIONS

Despite high community vaccination coverage, measles outbreaks can occur among clusters of intentionally undervaccinated children, at major cost to public health agencies, medical systems, and families. Rising rates of intentional undervaccination can undermine measles elimination.

Hepatitis and jaundice associated with measles in young adults. An analysis of 65 cases

We analyzed the clinical course of 65 adult patients hospitalized because of measles during the years 1975 and 1981-1982. Liver involvement was found in 80% (52/65) of the patients, five patients had clinical jaundice. The disturbances of liver function tests reached their peak values between days 5 and 10 of the disease. In this study of measles in adulthood we have three observations of unusual interest: (1) hepatitis occurs commonly in the more severely ill patients and it may manifest clinically as jaundice; (2) long-term follow-up (up to seven years) shows a clear tendency to complete resolution of the liver damage; (3) there is a clear correlation between the severity of hepatic involvement and the occurrence of secondary bacterial infections.