Reported measles in persons immunologically primed by prior vaccination

High Concentrations of Measles Neutralizing Antibodies and High-Avidity Measles IgG Accurately Identify Measles Reinfection Cases

In the United States, approximately 9% of the measles cases reported from 2012 to 2014 occurred in vaccinated individuals. Laboratory confirmation of measles in vaccinated individuals is challenging since IgM assays can give inconclusive results. Although a positive reverse transcription (RT)-PCR assay result from an appropriately timed specimen can provide confirmation, negative results may not rule out a highly suspicious case. Detection of high-avidity measles IgG in serum samples provides laboratory evidence of a past immunologic response to measles from natural infection or immunization. High concentrations of measles neutralizing antibody have been observed by plaque reduction neutralization (PRN) assays among confirmed measles cases with high-avidity IgG, referred to here as reinfection cases (RICs). In this study, we evaluated the utility of measuring levels of measles neutralizing antibody to distinguish RICs from noncases by receiver operating characteristic curve analysis. Single and paired serum samples with high-avidity measles IgG from suspected measles cases submitted to the CDC for routine surveillance were used for the analysis. The RICs were confirmed by a 4-fold rise in PRN titer or by RT-quantitative PCR (RT-qPCR) assay, while the noncases were negative by both assays. Discrimination accuracy was high with serum samples collected ≥3 days after rash onset (area under the curve, 0.953; 95% confidence interval [CI], 0.854 to 0.993). Measles neutralizing antibody concentrations of ≥40,000 mIU/ml identified RICs with 90% sensitivity (95% CI, 74 to 98%) and 100% specificity (95% CI, 82 to 100%). Therefore, when serological or RT-qPCR results are unavailable or inconclusive, suspected measles cases with high-avidity measles IgG can be confirmed as RICs by measles neutralizing antibody concentrations of ≥40,000 mIU/ml.

Risk factors for measles in children younger than age 8 months: A case-control study during an outbreak in Guangxi, China, 2013

BACKGROUND

Following a period (2009-2012) during which zero measles cases were reported, a measles outbreak occurred in 2013 in Bama County, Guangxi, China, that involved more than 100 children younger than age 8 months. We aimed to identify the pitfalls and risk factors while implementing the control measures.

METHODS

An outbreak investigation and a case-control study was conducted among children younger than age 8 months. The serum specimens of the study subjects and their mothers were tested for measles immunoglobulin M and immunoglobulin G.

RESULTS

The attack rate was 2.3/1,000 population. The median (interquartile range) age was 18.6 months (7.9-52.8 months). The coverage of 2-dose measles-containing vaccine was only 34%. The case-control study revealed 2 independent risk factors: low education level of main caregiver (odds ratio [OR], 2.86; 95% confidence interval [CI], 1.31-6.22) and visiting a hospital 7-21 days before the date of symptoms onset (OR, 9.84; 95% CI, 4.27-22.67). The population attributable fraction of the latter was 52.8%. The mothers of the cases had nonsignificantly higher levels of immunoglobulin M and were significantly more likely to have protective levels of immunoglobulin G than those of the controls. This suggests a reactive rather than protective role of the antibody to the child's infection.

CONCLUSIONS

In a near-elimination but low measles-containing vaccine coverage community, supplementary immunization activities should be emphasized for children and women who are potential future mothers. The minimum age of measles-containing vaccine should be further reduced. Hospital measles transmission must also be strictly prevented.

Risk analysis for measles reintroduction after global certification of eradication

BACKGROUND

Measles virus will continue to exist after certification of global eradication as virus stocks and infectious materials held in laboratories, in persistently and chronically infected individuals, and possibly in undetected foci of transmission. A literature search was undertaken to identify and evaluate the main risks for reintroduction of measles transmission in the absence of universal measles immunization.

METHODS

A qualitative risk assessment was conducted following a series of literature searches using the PubMed database.

RESULTS

If the criteria for global certification of eradication are stringent and require rigorous validation, then the risk of undetected measles transmission after certification is very low. Risk of unintentional reintroduction from any source, including persistent infections and laboratory materials is low to very low but depends on the extent of measles vaccine use. If immunization levels decrease, measles will become a credible agent for bioterrorism through intentional release.

CONCLUSIONS

Posteradication risks are low and should not deter any attempt at measles eradication. More information on measles transmission dynamics and the role of atypical infections is required to determine requirements for global certification of eradication. Posteradication risks would be minimized through development and implementation of an international risk management strategy, including requirements for a posteradication vaccine stockpile.

Clinical features of measles according to age in a measles epidemic

The purpose of this study was to retrospectively investigate the relationship between age and clinical manifestations and laboratory findings in patients with measles. The study included 216 patients admitted to a hospital in Daejeon, 1 of the largest cities in South Korea, during the 2000-2001 measles outbreak: very young children (<2 y old; 159 patients), school age children (9-11 y old; 34 patients), and young adults (>16 y old; 23 patients). Few of the very young children (9%), but most of the older children (86%) had a history of a prior measles-mumps-rubella vaccination. There were no statistical differences between the 3 groups in terms of the total duration of fever, length of hospitalization, occurrence of complications (defined as hospitalization for more than 7 d) or anti-measles IgM positivity. A reduction in the number of white blood cells and lymphocytes was observed in all age groups. The levels of C-reactive protein were not different between very young children and older children, but hepatic involvement was more prevalent in young adults. In conclusion, the clinical course including the complications experienced was similar in all the measles patients regardless of age.

The changing epidemiology of hospitalized pediatric patients in three measles outbreaks

OBJECTIVES

To assess the demographic and clinical findings of measles patients during three epidemics from 1989 to 2001.

METHODS

A total 520 medical records of measles patients were analyzed retrospectively and divided into three groups; those who were admitted during 1989-1990 (group I, 116 patients), those admitted during 1993-1994 (group II, 127 patients), and those admitted during 2000-2001 (group III, 277 patients).

RESULTS

For the age distribution, there was no difference in the proportion of < 2 years of age (61%, 58% and 57%, respectively) for the three groups. However, in each outbreak, there were significant differences in the distribution of > or = 2 years children who had mostly received one-dose measles-mumps-rubella (MMR) vaccination. The age distribution had changed with a significant increase in older children in subsequent outbreaks. In the last 2000-2001 outbreak, there was a pattern for increased attack rates with increasing interval since the initial vaccination. There was no statistical difference between the three groups in gender ratio, MMR vaccination rate in > or = 2 years of age, duration of fever, and complications. No difference was found in all the clinical and laboratory parameters between the anti-measles IgM antibody negative patients and the positive patients.

CONCLUSIONS

The age distribution of admitted children with measles in each outbreak has changed over time since the introduction of one-dose MMR vaccination. This finding suggests that the secondary vaccine failure may have played a large role in the last measles outbreak.

The clinical significance of measles: a review

Forty years after effective vaccines were licensed, measles continues to cause death and severe disease in children worldwide. Complications from measles can occur in almost every organ system. Pneumonia, croup, and encephalitis are common causes of death; encephalitis is the most common cause of long-term sequelae. Measles remains a common cause of blindness in developing countries. Complication rates are higher in those <5 and >20 years old, although croup and otitis media are more common in those <2 years old and encephalitis in older children and adults. Complication rates are increased by immune deficiency disorders, malnutrition, vitamin A deficiency, intense exposures to measles, and lack of previous measles vaccination. Case-fatality rates have decreased with improvements in socioeconomic status in many countries but remain high in developing countries.

New combination vaccines

Physicians can achieve full vaccination at each of the recommended visits by administering three or four injections, but for infants, four injections seem to be a maximum in light of the size of the infant thigh, which is the preferred injection site. Thus, physicians must make room for all of the new vaccines on the horizon. To accomplish that task, combinations will be necessary. Progress toward that goal is occurring.

Nonclassic measles infections in an immune population exposed to measles during a college bus trip

This study investigated the frequency of mild or asymptomatic measles infections among 44 persons exposed to a student with measles during a 3-day bus trip using two buses. Questionnaires and serum samples were obtained 26-37 days after the trip. All participants had detectable measles-neutralizing antibodies, and none developed classic measles symptoms. Ten persons (23%) were IgM positive for measles, indicating recent infection. Among previously vaccinated IgM-negative persons, those who rode on bus A with the index case-patient had significantly higher microneutralization titers than those on bus B (P= .001), suggesting that some persons on bus A were infected but were IgM negative at the time of the study. Mild or asymptomatic measles infections are probably very common among measles-immune persons exposed to measles cases and may be the most common manifestation of measles during outbreaks in highly immune populations.

Immunoglobulin M antibody response to measles virus following natural virus infection, primary vaccination, and reexposure to the virus

Evaluation of the measles virus ELISA kit (Merck) to detect specific IgM as an indicator of primary measles antibody response was carried out. A modification of the manufacturer's cutoff value interpretation was introduced to allow for equivocal results in addition to positive and negative ones. With this modification, the test assayed gave an overall reproducibility of 96.16%. The IgM seropositivity rate for seroneutralization-confirmed measles cases was 100% for naturally infected measles subjects and 90% for primary measles vaccinated subjects. Individuals with positive neutralizing antimeasles antibodies in close contact with a confirmed measles case gave the following measles IgM ELISA results: 54.54% negative, 9.09% positive, and 36.36% equivocal, showing a booster with IgM antibody response on reexposure to the virus. Positive subjects with neutralizing antimeasles antibodies without recent contact with a measles case gave negative IgM results. IgM seropositivity was strongly associated with IgG seroconversion and clinical measles (p < 0.0001). The technique assayed performed adequately for the confirmation of both measles natural infection and primary vaccination and for the differentiation of primary and secondary antibody response, taking into account the modification in the cutoff value interpretation introduced and providing that the serum samples are obtained between days 5 and 30 after onset of rash.

Five cases of measles secondary vaccine failure with confirmed seroconversion after live measles vaccination

We report 5 patients with secondary vaccine failure (SVF) who were infected with natural measles 2, 5, 5, 7 and 12 years, respectively, after vaccination with further attenuated live measles vaccine during infancy. Their seroconversion had been confirmed after vaccination. Three of the 5 patients had mild (modified) measles, while the remaining 2 patients had typical measles. The hemagglutination inhibition antibody titers to measles virus in paired acute and convalescent sera showed a secondary response pattern in 4/5 patients, and a primary response pattern was present in the remaining patient. Measles IgM antibodies were present in all patients during the convalescent stage. The patient with the primary response pattern may have had a decrease in the B cell memory during the 5-year period between vaccination and infection. This may be the first SVF case report that confirms the existence of completely waning immunity in recipients of the further attenuated live measles vaccines.

Clinical and epidemiological findings during a measles outbreak occurring in a population with a high vaccination coverage

From March 1991 to April 1992, 250 measles suspected cases were studied in the Municipality of Niterói, State of Rio de Janeiro. The median age found was 11 years and 76.0% of the cases were in school age children. Exposure histories were present in 149 patients and schools were the most frequent sites of transmission (45.0%). Vaccination status was known for 127 studied cases and 76.4% of them had received measles vaccine before their first birthday. One or more complications were reported for 68 cases and in 8.9% of the studied cases hospitalization was required. Frequency of complications varied according to each age group studied and were more commonly encountered among children < 1 year of age (55.6%). The history of previous vaccination did not diminish the number of complications of the cases studied. The results of this work show changes in age distribution of measles leading to sizeable outbreaks among teenagers and young adults.

Serological findings during a measles outbreak occurring in a population with high vaccine coverage

From March 1991 to April 1992, serum samples for IgM detection were collected from 112 clinical measles cases reported to the Health Department of Niterói, State of Rio de Janeiro. The positivity exceeded 90% for specimens collected from the 5th to the 29th day after the onset of the disease. After day 30 a decline in IgM detection was observed, although positivity has been detected up to 90 days after the onset of the symptoms. Forty-four patients (48.9%) with an IgM response had a history of prior measles vaccination. In 5 of the 22 measles-IgM negative cases the infection was due to other agents (rubella: 4 cases, dengue: 1 case). These results show that sensitivity of the test employed for confirming suspected measles cases is high, even in vaccinated patients.

Epidemiology of measles in Taiwan: dynamics of transmission and timeliness of reporting during an epidemic in 1988-9

We analysed nation-wide reported measles cases during the 1988-9 epidemic and found that longer duration and wider spread were two major characteristics of the outbreak. All the 22 county/city index cases were reported with a delay of > 4 days and 64% were aged 5-14 years. This epidemic occurred mainly among 5-14-year-old school-children (59%), infants under 1 year (19%), and pre-school children (18%). The overall attack rate was 0.63 cases per 10,000 population, with the highest attack rate (7.4 cases per 10,000 population) occurring in infants. Among 280 confirmed cases < 15 months of age, 9-month-old infants (42 cases) had a higher risk of measles and peaked at 10 months (49 cases). This epidemic started in March 1988 among 5-9-year-old children in the northern suburban area, then spread to Taipei City and neighbouring counties or cities. It continued to spread from the northern to southern and western areas during the summer vacation and New Year holidays. Multiple logistic regression analysis showed that the delay of measles reporting was strongly associated with the cases infected early in the epidemic (OR = 6.9, P < 0.001) and reported from teaching hospitals (OR = 2.6, P < 0.001). The reappearance of high attack rates among 5-9-year-old children in the 1985 and 1988-9 measles epidemics in Taiwan indicated the persistence of pockets of susceptible individuals even after mass immunization.

Two independent outbreaks of measles in partially vaccinated junior high schools in Tottori, Japan

We analyzed retrospectively a relative risk of measles attacks in vaccinated vs. unvaccinated students using two independent outbreaks in Japan. The first involved 33/328 (10%) students where 64% students and 30% measles cases had been vaccinated. The second involved 27/241 (11%) students where 81% students and 48% measles cases had been vaccinated. The attack rates of vaccinated vs. unvaccinated students were significantly low (p < 0.001), but they accounted 25% in both episodes. The statistically significant clinical features among vaccinated and unvaccinated cases included the average duration of fever, 5.16 +/- 1.71 vs. 6.67 +/- 2.19 days (p = 0.01) and the incidence of complications, 0 vs. 25%, respectively. These results suggested that the measles in vaccinated cases were mostly due to secondary failures.

Measles antibody: comparison of long-term vaccination titres, early vaccination titres and naturally acquired immunity to and booster effects on the measles virus

A two-dose vaccination programme, using a combined measles, mumps and rubella vaccine (MMR) and administration at the ages of 18 months and 12 years, was introduced into Sweden in 1982. Since the combined MMR vaccine was introduced, a yearly evaluation of the immunity patterns and seroconversion rates in 12-year-old children has been carried out. This study includes three study groups. All groups consisted of pre- and postvaccination samples from 12-year-old children taken in connection with the MMR immunization. There were 332 paired samples from children who 8-10 years previously had received live measles vaccine. Prevaccination sera from these children represent late postvaccination titres. The postvaccination sera of 49 children seronegative to measles before vaccination, obtained 2 months after vaccination, represent early postvaccination immunity. Ninety-five children who had not been vaccinated earlier and who were seropositive to measles represent naturally acquired immunity. All samples were studied by an enzyme-linked immunosorbent assay (ELISA). Sera from children with late postvaccination immunity had significantly lower titres than children in group 2, who represented early postvaccination sera (p < 0.001). Children with naturally acquired immunity had significantly higher titres than children with vaccine-induced immunity titres (p < 0.001). After revaccination of the previously vaccinated children, a significant booster rise was seen (p < 0.001). After revaccination of children with naturally acquired immunity, no significant booster effect was observed. Sixty-five children of the 332 (20%) previously vaccinated children had no or borderline measles titres prior to the booster. The study suggests that the vaccine-induced measles antibodies decline with time and may fall under the protective level.(ABSTRACT TRUNCATED AT 250 WORDS)

Studies on manifestations of canine distemper virus infection in an urban dog population

An upsurge of canine distemper was recognized at the beginning of 1991 in the urban dog population of the Copenhagen area. The outbreak had the characteristics of a virulent morbillivirus introduction in a partly immune population, where the disease primarily was manifested in young individuals. Testing of single serum samples for the presence of canine distemper virus (CDV) IgM antibodies using an IgM ELISA confirmed current and recent CDV infections in an urban dog population, where the use of attenuated CDV vaccines was widespread. In 49 out of 66 sera from clinical cases suspected of canine distemper we detected CDV IgM antibodies, as compared to the detection of viral antigen by indirect immunofluorescence in 27 of 65 specimens of conjunctival cells. The antigenic make-up of isolates from acute and subacute clinical cases was investigated with a panel of 51 monoclonal antibodies directed against CDV and the related phocine distemper virus. The isolates exhibited an homogeneous reaction pattern and shared overall antigenic characteristics of the CDV prototype. The majority of cases were diagnosed among unvaccinated dogs and individuals with unknown or obscure vaccination record. However, severe clinical cases were also diagnosed in vaccinated individuals.

Immunoglobulin M antibody response to measles virus following primary and secondary vaccination and natural virus infection

The use of IgM antibody detection for the classification of the primary and secondary measles antibody response in persons following primary and secondary vaccination and natural measles virus infection was examined. Of 32 nonimmune children receiving primary measles vaccination, 31 (97%) developed IgM antibodies, consistent with a primary antibody response. Of 21 previously vaccinated children with low levels of preexisting IgG antibodies who responded to revaccination, none developed detectable IgM antibodies, whereas 33 of 35 (94%) with no detectable preexisting IgG antibodies developed an IgM response. Of a sample of 57 measles cases with a prior history of vaccination, 55 (96%) had detectable IgM antibodies. Of these, 30 (55%) were classified as having a primary antibody response and 25 (45%) a secondary antibody response based on differences in their ratios of IgM to IgG antibodies. Differences in the severity of clinical symptoms between these 2 groups were consistent with this classification scheme. These findings suggest that 1) an IgM response follows primary measles vaccination in the immunologically naive, 2) an IgM response is absent on revaccination of those previously immunized, and 3) an IgM response may follow clinical measles virus infection independent of prior immunization status.

The dilemma of AIDS vaccine and therapy. Possible clues from comparative pathogenesis with measles

AIDS viruses, because of their unique properties, are extraordinary. Past successes achieved with vaccines against ordinary viruses do not provide the guidelines needed to develop successful vaccines against HIV. Neither vaccines nor drugs can be relied upon to provide an answer to AIDS. AIDS is a disease of immune dysfunction and destruction, and an alternative to prevention of infection or cure might lie with elimination of the clinical consequences of infection. This might find a basis in precise definition of its pathogenesis. The enormity of possible pathogenetic changes in HIV infection invites simplification, and might be aided by a search for clues among ordinary viruses in which there is a less complicated biology and spontaneous recovery from infection. Measles virus infection presents analogies to AIDS, especially in the induction of anergy and increased mortality, in the long term, from diseases other than measles as observed in children infected during early life. This was demonstrated recently in increased deaths, all causes, during a three-year period among infants who were given live measles virus vaccine of high infectivity titer during early infancy, sometimes in the presence of maternal antibody. AIDS and measles may be diseases of similar pathogenesis, but with the difference that AIDS immunopathology is progressive while that for measles is regressive.

Secondary immune response in a vaccinated population during a large measles epidemic

The rates of secondary immune response (SIR) and secondary vaccine failure (SVF) during a measles epidemic (10,184 notifications) were evaluated. A patient with SIR was defined as a subject for whom all sera were immunoglobulin G (IgG) positive and IgM negative with a significant increase in complement fixation titer. A patient with SVF was defined as a vaccinated symptomatic subject showing a SIR. Sequential sera from 898 subjects were tested for measles antibody by enzyme-linked immunosorbent assay (IgG and IgM) and by complement fixation. Evidence of recent anti-measles virus specific immune response was found in 496 subjects (55.5%). The vaccination rate was estimated at 74.6% (99% confidence interval [CI], 67.9 to 80.7%). The number of exposed vaccinated subjects was estimated at 370 (74.6% of 496). The SIR rate was 4.03% (20 of 496) (99% CI, 2.1 to 6.9%) among subjects with immune response. These 20 subjects were 2 with measles (Centers for Disease Control's definition), 6 with measles with rash of unknown duration, 8 with presumed measles with either rash or fever, 3 asymptomatic subjects (2 with recent contact with a measles case), and 1 undocumented subject. Since 3 patients with SIR were asymptomatic and 2 others were documented as not vaccinated, there was a maximum of 15 probable occurrences of SVF among the 20 patients with SIR. The SVF rate among exposed vaccinated subjects was estimated at 4.05% (15 of 370) (99% CI, 1.9 to 7.5%). In conclusion, neither prior vaccination nor detectable SIR ensures protective immunity. Measles virus may induce asymptomatic SIR in IgG-seropositive subjects. SVF led to typical or modified measles but did not seem to have played an important role during this epidemic.

Evaluation of monoclonal antibody-based capture enzyme immunoassays for detection of specific antibodies to measles virus

Monoclonal antibodies to the hemagglutinin protein, fusion protein, phosphoprotein, matrix protein, and nucleoprotein of measles virus were evaluated as detector antibodies in capture enzyme immunoassays (EIAs) for the detection of specific serum immunoglobulin G (IgG), IgA, and IgM antibodies to measles virus. A pool of monoclonal antibodies to hemagglutinin protein and nucleoprotein proved optimal and was further evaluated. Specific IgM was detected in 97% of adolescents with clinical measles, 97% of infants 3 weeks postvaccination, and less than 1% of normal serum specimens. Specific IgA antibodies were found in 97% of adolescents with clinical measles, 97% of infants 3 weeks postvaccination, and less than 1% of normal serum specimens. Specific IgA antibodies were found in 97% of clinical measles cases and vaccinees, in 26% of healthy persons, and in 36% of infants 8 months postvaccination; consequently, IgA antibodies were not a useful indicator of recent measles infection. A significant increase in IgG antibodies between paired specimens was detected in 92% of clinical cases and all vaccinees. Only 59% of infant specimens had persistent IgG antibodies as detected by capture EIA at 8 months postvaccination, whereas all specimens had antibodies as detected by hemagglutination inhibition and plaque neutralization. An alternative indirect EIA, in which antigen was directly absorbed to the solid phase, was more sensitive than the capture design, detecting IgG antibodies in all infants postvaccination. When standardized with a microneutralization assay for the detection of persistent antibodies, the indirect IgG EIA gave predictive values for positive and negative tests exceeding 90%. Our capture IgM and indirect IgG EIAs provide a practical combination of serologic tests for the determination of acute measles virus infection and past exposure to measles virus or vaccine, respectively.

Measles vaccines

Measles vaccine is one of the safest and most effective vaccines currently available. Use of the vaccine has decreased the incidence of measles in both developed and developing countries. Nevertheless, preventable morbidity and mortality continue to occur. In the United States, the measles problem differs when it occurs among preschool-aged children or school-aged children. The former is a due to insufficient vaccine delivery. For measles in school-aged and college students, the problem is primarily vaccine failure, which should eventually be solved by a two-dose schedule. In developing countries, the major problem is vaccine delivery. Use of Edmonston-Zagreb measles vaccine in developing countries offers the promise of reducing disease rates in young infants; however, in both the United States and in developing countries, increasing immunization levels is essential.