Sustained transmission of mumps in a highly vaccinated population: assessment of primary vaccine failure and waning vaccine-induced immunity

Immune responses to mumps vaccine in adults who were vaccinated in childhood

BACKGROUND

In a mumps outbreak in the United States, many infected individuals were adults who had received 2 doses of mumps vaccine. The persistence of cellular immunity to mumps vaccine has not been defined.

METHODS

This was an observational, nonrandomized cohort study evaluating cell-mediated and humoral immunity to mumps in 10 vaccinated and 10 naturally immune adults. Mumps-specific T cell activation and interferon (IFN)-gamma production were measured using lymphoproliferative and flow cytometry assays, and mumps immunoglobulin (Ig) G was measured using enzyme-linked immunosorbent assay.

RESULTS

T cell immunity to mumps was high in both groups; 70% of vaccinated and 80% of naturally immune individuals had a positive (> or =3) stimulation index (SI) (P = 1.0). The mean percentages of mumps-specific CD4+ T cells that expressed CD69 and produced IFN-gamma were equivalent in the 2 groups: 0.06% and 0.12%, respectively (P = .11). The mean SIs in the groups were also equivalent, although IFN-gamma concentrations from cultures stimulated with mumps antigen were higher in naturally immune adults than in vaccinated adults (P < or = .01). All adults were positive for mumps IgG.

CONCLUSION

T and B cell immunity to mumps was detected in adults at least 10 years after immunization. Except for IFN-gamma release, responses in vaccinated adults paralleled those observed in naturally immune individuals.

Long-term persistence of mumps antibody after receipt of 2 measles-mumps-rubella (MMR) vaccinations and antibody response after a third MMR vaccination among a university population

BACKGROUND

High attack rates among vaccinated young adults reported during the 2006 mumps outbreak in the United States heightened concerns regarding mumps vaccine failure.

METHODS

Serum specimens from university students and staff were tested for mumps immunoglobulin (Ig) G by enzyme immunoassay (EIA). A subset of participants vaccinated for < or =5 years and > or =15 years were tested by neutralizing antibody (NA) assay. Persons seronegative by EIA were offered a third dose of measles-mumps-rubella vaccine (MMR3), and serum specimens were obtained 7-10 days and 2-3 months after its administration.

RESULTS

Overall, 94% (95% confidence interval [CI], 91%-96%) of the 440 participants were seropositive. No differences existed in seropositivity rates by sex, age, age at receipt of the second dose of MMR vaccine (MMR2), or time since receipt of MMR2 (P = .568). The geometric mean titer (GMT) of NA among persons vaccinated with MMR2 during the previous 1-5 years was 97 (95% CI, 64-148), whereas, among those vaccinated > or =15 years before blood collection, the GMT was 58 (95% CI, 44-76) (P = .065). After MMR3, 82% (14/17) and 91% (10/11) seroconverted in 7-10 days and 2-3 months, respectively.

CONCLUSIONS

Lower levels of NA observed among persons who received MMR2 > or =15 years ago demonstrates antibody decay over time. MMR3 vaccination of most seronegative persons marked the capacity to mount an anamnestic response.

Immunogenicity and safety of a novel formalin-inactivated and alum-adjuvanted candidate subunit vaccine for mumps

While an attenuated vaccine against mumps has played a role in controlling the epidemic of this disease worldwide, some problems with efficacy and safety of the vaccine are still present. In the work described here, a novel mumps vaccine with good immunity and safety was developed by selecting an antigen component of the mumps virus. The results suggest that this purified antigen vaccine is immunogenic in animals and is capable of inducing a specific neutralizing antibody response against viral HN, but not against other viral proteins. The clinical and pathological observations after challenge of vaccinated rhesus monkeys indicated further that the immune response induced by this vaccine provided complete protection from wild-type virus infection. Furthermore, the immunological analysis and clinical observation of experimental monkeys that were immunized with the vaccine, followed by infection with wild-type virus, suggest that no abnormal changes in expression of inflammatory cytokines and no clinical allergic reaction were found at 1 month after challenge.

Mumps vaccination coverage and vaccine effectiveness in a large outbreak among college students--Iowa, 2006

Following implementation of a routine childhood two-dose measles-mumps-rubella vaccination strategy, mumps disease levels dropped dramatically in the US and an elimination goal was set for 2010. However, a 2006 epidemic involved >5700 cases nationwide, with many reported among fully vaccinated college students. In an outbreak in two Iowa colleges, we investigated: (1) vaccination coverage using electronic records verified by provider records and (2) vaccine effectiveness assessed by comparison of dose-specific attack rates. Mumps was classified as typical (parotitis/orchitis) or atypical (parotid tenderness or submandibular/sublingual adenitis). Two-dose mumps vaccination coverage was 90% both for the student population (2128/2363) and case-students (97/108). Two-dose vaccine effectiveness was 76-88% with no significant difference for attack rates between one and two doses. Among two-dose vaccine recipients, 74% of the population (1482/2009) and 79% of the case-students (75/95) had received the second dose >10 years before. A large mumps outbreak occurred despite high two-dose vaccination coverage in a population most of whom had received the second dose >10 years before. Two-dose vaccine effectiveness was similar to previous one-dose estimates. Further studies are needed to examine the persistence of two-dose mumps vaccine-induced immunity and to determine whether US mumps elimination can be achieved with the current vaccination strategy.

Molecular identification of two genotypes of mumps virus causing two regional outbreaks in Asturias, Spain

BACKGROUND

In spite of universal vaccination, several sporadic cases of mumps infection, which could produce outbreaks, are detected every year in different countries.

OBJECTIVE

Mumps virus strains causing two regional outbreaks in Asturias (Spain) were phylogenetically characterized.

STUDY DESIGN

Mumps virus strains, which were detected in samples from patients belonging to two regional outbreaks in Asturias, were characterized by sequencing of the SH gene and further alignment to homologous sequences of representative strains of the different mumps genotypes.

RESULTS

Two different strains (Ast/SP02 and Ast/SP07) were isolated. Sequence analysis revealed that while Ast/SP02 belonged to genotype H, Ast/SP07 was phylogenetically close to UK02-19, a reference strain for a new genotype. Both strains belonged to different genotypes from those used in the vaccination (Jeryl-Lynn strain is genotype A).

CONCLUSION

Mumps virus strains different from those used in vaccination program can cause mumps outbreaks even in vaccinated patients.

Recent resurgence of mumps in the United States

BACKGROUND

The widespread use of a second dose of mumps vaccine among U.S. schoolchildren beginning in 1990 was followed by historically low reports of mumps cases. A 2010 elimination goal was established, but in 2006 the largest mumps outbreak in two decades occurred in the United States.

METHODS

We examined national data on mumps cases reported during 2006, detailed case data from the most highly affected states, and vaccination-coverage data from three nationwide surveys.

RESULTS

A total of 6584 cases of mumps were reported in 2006, with 76% occurring between March and May. There were 85 hospitalizations, but no deaths were reported; 85% of patients lived in eight contiguous midwestern states. The national incidence of mumps was 2.2 per 100,000, with the highest incidence among persons 18 to 24 years of age (an incidence 3.7 times that of all other age groups combined). In a subgroup analysis, 83% of these patients reported current college attendance. Among patients in eight highly affected states with known vaccination status, 63% overall and 84% between the ages of 18 and 24 years had received two doses of mumps vaccine. For the 12 years preceding the outbreak, national coverage of one-dose mumps vaccination among preschoolers was 89% or more nationwide and 86% or more in highly affected states. In 2006, the national two-dose coverage among adolescents was 87%, the highest in U.S. history.

CONCLUSIONS

Despite a high coverage rate with two doses of mumps-containing vaccine, a large mumps outbreak occurred, characterized by two-dose vaccine failure, particularly among midwestern college-age adults who probably received the second dose as schoolchildren. A more effective mumps vaccine or changes in vaccine policy may be needed to avert future outbreaks and achieve the elimination of mumps.

The epidemiology of mumps in Italy

In Italy, although vaccination has been recommended for a number of years, vaccination coverage for mumps is still sub-optimal. The objective of the present study was to evaluate the seroprevalence of mumps antibodies in the Italian population, stratified by age, gender and geographical area. The proportion of individuals positive for mumps antibodies remained stable in the age classes 0-11 months and 1 year (25.4% and 30.8%, respectively) and showed a continuous increase after the second year of life. The percentage of susceptible individuals was higher than 20% in persons 2-14 years of age and exceeded 10% in persons 15-39 years of age. No statistically significant differences were observed by gender or geographical area. Comparison between these results and the data obtained from a 1996 survey showed a statistically significant increase in seroprevalence in the age class 2-4 years. No changes were observed in the other age-groups. The results of this study confirm that the efforts made in recent years to improve vaccination coverage within the second year of life should be strengthened.

Mumps virus reinfection is not a rare event confirmed by reverse transcription loop-mediated isothermal amplification

Clinically apparent mumps reinfection is considered extremely rare, but several cases have been suspected of reinfection in an out-patient clinic. In this study, virological examination, virus isolation, the reverse transcription loop-mediated isothermal amplification (RT-LAMP), and IgG and IgM EIA antibodies, were examined in order to identify mumps reinfection. Patients were divided into three categories; the reinfection group comprised 29 patients with a history of natural infection, the vaccine-failure group consisted of 37 patients with an immunization history, and two patients had histories of both immunization and mumps infection. Another 25 patients were enrolled as a primary infection group. Mumps virus was isolated in 5 (17%) and the genome was detected in 12 (41%) of 29 in the reinfection group. Reinfection was confirmed in 21/28, demonstrating high avidity of IgG EIA. Mumps virus was isolated in 15 (41%) and there was a higher positivity of genome amplification in 25 (68%) of 37 patients in the vaccine-failure group. Among these, 23 were confirmed as secondary vaccine failure by high avidity IgG EIA serology. In the primary infection group, the isolation rate and genome detection rate was higher in 16 (64%) and in 18 (72%) of 25 patients, respectively. There was no significant difference in virus load among the three groups but high mumps virus load was suspected in the IgM EIA-positive group based on the shorter amplification time on RT-LAMP. Mumps virus reinfection was confirmed by RT-LAMP and an IgG avidity test and was not a rare event.

Effectiveness of previous mumps vaccination during a summer camp outbreak

OBJECTIVES

Mumps is a vaccine-preventable disease that may cause outbreaks. In July 2005, an outbreak of mumps occurred during a children's summer camp in upstate New York. An investigation was initiated to describe the cases and evaluate vaccine effectiveness.

METHODS

A retrospective cohort study was conducted among 541 children from the United States and abroad who attended a 1- or 2-month overnight summer camp. Patients with mumps were interviewed; serologic analysis was conducted for 6 case patients. Vaccine effectiveness was calculated by retrospective review of immunization records for 507 attendees who were eligible for vaccination and had verified immunization history.

RESULTS

Thirty-one camp attendees were identified as having mumps (attack rate: 5.7%); 5 (83%) of 6 patients tested had positivity for mumps immunoglobulin M. Of the 507 participants (including 29 patients) with available immunization history, 440 (including 16 [87%] patients) were 2-dose recipients of mumps vaccine (attack rate: 3.6%); 46 participants (including 4 [9%] patients) were 1-dose recipients (attack rate: 8.7%); and 21 (including 9 [4%] patients) were unvaccinated (attack rate: 42.9%). Vaccine effectiveness was 92% for 2 doses and 80% for 1 dose.

CONCLUSIONS

Outbreaks of mumps in settings such as summer camps can occur despite high vaccination rates. Vaccine effectiveness for 2 mumps vaccinations was greater than vaccine effectiveness for 1 mumps vaccination. Therefore, recommendation of 2 mumps vaccinations for summer camp participants continues to be appropriate. Control of mumps disease relies on broad vaccination coupled with correct clinical diagnosis and strict control measures.

Persistence of antibodies induced by measles-mumps-rubella vaccine in children in India

Antibody levels in 41 Indian girls were measured 6 years after measles-mumps-rubella (MMR) vaccination. Rates of seropositivity were 88% (measles antibodies), 95% (mumps antibodies), and 100% (rubella antibodies). The MMR vaccine induces long-term immunity in a majority of vaccinees; however, due to the observation of some seronegative vaccinees, the policy of administering a second dose of the MMR vaccine seems appropriate.

Real-time reverse transcription-PCR assay for detection of mumps virus RNA in clinical specimens

The mumps virus is a negative-strand RNA virus in the family Paramyxoviridae. Mumps infection results in an acute illness with symptoms including fever, headache, and myalgia, followed by swelling of the salivary glands. Complications of mumps can include meningitis, deafness, pancreatitis, orchitis, and first-trimester abortion. Laboratory confirmation of mumps infection can be made by the detection of immunoglobulin M-specific antibodies to mumps virus in acute-phase serum samples, the isolation of mumps virus in cell culture, or by detection of the RNA of the mumps virus by reverse transcription (RT)-PCR. We developed and validated a multiplex real-time RT-PCR assay for rapid mumps diagnosis in a clinical setting. This assay used oligonucleotide primers and a TaqMan probe targeting the mumps SH gene, as well as primers and a probe that targeted the human RNase P gene to assess the presence of PCR inhibitors and as a measure of specimen quality. The test was specific, since it did not amplify a product from near-neighbor viruses, as well as sensitive and accurate. Real-time RT-PCR results showed 100% correlation with results from viral culture, the gold standard for mumps diagnostic testing. Assay efficiency was over 90% and displayed good precision after performing inter- and intraassay replicates. Thus, we have developed and validated a molecular method for rapidly diagnosing mumps infection that may be used to complement existing techniques.

Mumps outbreaks in Canada and the United States: time for new thinking on mumps vaccines

Mumps epidemics in Canada and the United States prompted us to review evidence for the effectiveness of 5 different vaccine strains. Early trials with the Jeryl Lynn vaccine strain demonstrated an efficacy of approximately 95%, but in epidemic conditions, the effectiveness has been as low as 62%; this is still considerably better than the effectiveness of another safe strain, Rubini (which has an effectiveness of close to 0% in epidemic conditions). The Urabe vaccine strain has an effectiveness of 54%-87% but is prone to cause aseptic meningitis. Little epidemiological information is available for other vaccines. The Leningrad-Zagreb vaccine strain, which is widely used in developing countries and costs a fraction of what vaccines cost in the developed world, seems to have encouraging results; in 1 study, the effectiveness of this vaccine exceeded 95%. Aseptic meningitis has also been reported in association with this vaccine, but the benign nature of the associated meningitis was shown recently in Croatia. Also, the Leningrad-3 strain seems to be effective but causes less-benign meningitis. No mumps vaccine equals the best vaccines in quality, but the virtually complete safety of some strains may not offset their low effectiveness. Epidemiological data are pivotal in mumps, because serological testing is subject to many interpretation problems.

Investigation of mumps vaccine failures in Minsk, Belarus, 2001–2003

The purpose of this study was to investigate mumps vaccine failures (VF) in a highly vaccinated population of Minsk, Belarus, and to investigate a possible role for virus strain-specific immunity. During our 3-year study period, 22 adults were admitted to the Infectious Diseases Hospital in Minsk with a diagnosis of mumps. A genotype H1 mumps virus (MuV) strain was identified in all patients. Of 15 patients from whom the paired sera were collected, 9 were confirmed to have been previously vaccinated. Serological examinations indicated primary VF in seven of these cases and secondary VF in two. Despite almost all vaccinated patients possessing MuV specific IgG, few possessed neutralizing antibody to the vaccine strain and titers were nominal. Importantly, none of the sera were able to neutralize a genotype H MuV strain. Our results demonstrate the importance of assaying for neutralizing antibody and support the assertion that antigenic differences between wild type and vaccine MuV strains may play a role in cases of breakthrough infection in vaccinees.

Mumps vaccine failure investigation in Novosibirsk, Russia, 2002-2004

The aims of this study were to estimate the importance of vaccine failure (VF) in cases of mumps during 2002-2004 in the city of Novosibirsk, Western Siberia, Russia, and to genotype the responsible virus strain. Mumps virus-specific RT-PCR testing of saliva was performed for 18 cases of mumps. Sera were tested for IgM and IgG, IgG avidity, and the ability to neutralise a panel of mumps viruses, including the Leningrad-3 mumps vaccine virus. Of the 12 patients for whom vaccination status was positively determined, 11 showed serological evidence of primary VF. Sequence analysis of virus RNA amplified from saliva revealed a genotype C2 virus in 2002, a genotype H2 virus in 2003, and both genotypes in 2004. Although several vaccinated patients were positive for mumps virus IgG at the time of first sampling, only nominal levels of neutralising antibody were detected, and these were effective in neutralising the vaccine strain, but not genotype C and H mumps virus strains. These results suggest that the majority of cases of mumps in vaccinees are caused by primary VF, defined as either a lack of seroconversion or a lack of IgG maturity, as based on avidity testing. The results also support the hypothesis that sera of low neutralising antibody titre have a limited ability to neutralise heterologous mumps virus strains, suggesting that antigenic differences between circulating and mumps vaccine virus strains may play a role in cases of breakthrough infection. Consistent with previous reports, mumps virus genotypes C and H continue to circulate in Novosibirsk.

Vaccine effectiveness estimates, 2004-2005 mumps outbreak, England

As vaccinated children approach adolescence, immunity wanes, which may contribute to outbreaks.

The United Kingdom and United States have recently experienced large outbreaks of mumps, which raises concerns about vaccine effectiveness. The effectiveness of the mumps component of the measles, mumps, rubella (MMR) vaccine was estimated using the screening method. In England from January 2004 through March 2005, 312 cases of mumps were reported in children eligible to have received 2 doses of MMR vaccine. Of these children, 52 (16.7%) had received 1 dose of MMR vaccine, and 97 (31.1%) had received 2 doses. Vaccine effectiveness was 88% (95% confidence interval [CI] 83%–91%) for 1 dose and 95% (95% CI 93%–96%) for 2 doses. The effectiveness of 1 dose declined from 96% (95% CI 81%–99%) in 2-year-olds to 66% (95% CI 30%–83%) in 11- to 12-year-olds, and the effectiveness of 2 doses declined from 99% (95% CI 97%–99.5%) in 5- to 6-year-olds to 86% (95% CI 74%–93%) in 11- to 12-year-olds (p<0.001 for 1 or 2 doses). Waning immunity may contribute to mumps outbreaks in older vaccinated populations.

Open randomized trial comparing the immunogenicity and safety of a new measles-mumps-rubella vaccine and a licensed vaccine in 12- to 24-month-old children

BACKGROUND

A trivalent measles-mumps-rubella (MMR) vaccine (MMR Berna) has been developed with a new mumps component, BBM-18, to replace a previously licensed MMR vaccine containing the Rubini mumps strain. Previous studies showed Rubini to confer insufficient long term protection against mumps infection. This study compared the immunogenicity and safety of MMR Berna, which is produced entirely in human diploid cells, with those of the licensed vaccine M-M-RVax (Merck & Co.).

METHODS

We vaccinated 467 subjects, 12-24 months of age, in an open, randomized (1:1), phase II, multicenter study. Antibody titers were determined for each vaccine component with a plaque neutralization test (PNT) and a commercial enzyme-linked immunosorbent assay. Solicited local and systemic reactions were recorded in subject diaries for 6 weeks after vaccination.

RESULTS

Seroconversion rates 6 to 8 weeks after vaccination for measles and rubella were statistically comparable for the 2 vaccines. However, mumps seroconversion rates were highly assay dependent, with significant differences being measured with the enzyme-linked immunosorbent assay (Berna, 77.4%; Merck, 91.3%; P < 0.001) but not the PNT (Berna, 84.8%; Merck, 87.6%; P = 0.42). The overall rate of systemic reactions was lower in the MMR Berna group (36.8% versus 45.9%; P < 0.05), including a significantly lower rate of fever of >38 degrees C (37.2% versus 51.8%; P < 0.01).

CONCLUSIONS

MMR Berna was statistically noninferior to M-M-RVax with respect to seroconversion rates, and the BBM-18 strain elicited a level of functional antimumps antibodies comparable to the Jeryl Lynn strain, as measured with the PNT. Overall, MMR Berna was better tolerated than the comparison vaccine, particularly with respect to the frequency of fever.

The effectiveness of the mumps component of the MMR vaccine: a case control study

In 1998/1999, an outbreak of mumps occurred among children of a religious community in North East London. A case control study was conducted to assess the effectiveness of the mumps component of the MMR vaccine. One hundred and sixty-one cases of mumps were identified and 192 controls were selected. Fifty-one percent of cases and 77% of controls had a history at least one MMR vaccination. The observed effectiveness of any MMR vaccination adjusted for age, sex and general practice was 69% (95% CI: 41-84%). This is consistent with the results of other observational studies of mumps containing vaccines, but lower than the immunogenicity of mumps vaccines reported by clinical trials. This discrepancy is because observational studies tend to underestimate vaccine effectiveness, and because immunogenicity is not necessarily an accurate biological marker of vaccine effectiveness. Two doses of vaccine were more effective (88% (95% CI: 62-96%)) than a single dose (64% (95% CI: 40-78%)). The current two-dose vaccination programme remains the best method for controlling mumps infection in the community.

Mumps virus-specific antibody titers from pre-vaccine era sera: comparison of the plaque reduction neutralization assay and enzyme immunoassays

Mumps virus-neutralizing antibodies are believed to be the most predictable surrogate marker of protective immunity. However, assays used to detect neutralizing antibodies, such as the plaque reduction neutralization (PRN) assay, are labor- and time-intensive and consequently are often supplanted by the more rapid and inexpensive enzyme immunoassay (EIA) technique. For virus infections for which international antibody standards exist and are bridged to clinical studies of protection (e.g., measles and rubella), the EIA has been successfully used to determine immune surrogate endpoints, yet no such international reference exists for mumps serology. Since both virus-neutralizing and nonneutralizing antibodies are measured in the EIA, in the absence of a mumps serological standard, the EIA may be prone to yielding false-positive results when utilized for assessing surrogate markers of protective immunity. Moreover, since mumps virus-specific antibody titers are generally low in comparison to antibody levels induced by other viruses and EIA procedures often employ relatively high serum dilution factors, the EIA may be prone to yielding false-negative results. To examine these issues, a PRN assay and two commercially available EIA kits were used to evaluate wild-type mumps virus serological responses in human serum samples from the pre-mumps vaccine era. Our results indicate that the PRN assay is a more sensitive and specific method of measuring serological responses to wild-type mumps virus.

Correlates of lymphoproliferative responses to measles, mumps, and rubella (MMR) virus vaccines following MMR-II vaccination in healthy children

Cell-mediated immunity (CMI) to measles, mumps, and rubella viral antigens plays a critical role in providing long-term protection against these infectious diseases. We examined CMI by measuring lymphoproliferative response induced in response to stimulation with the above three antigens following two doses of measles, mumps, and rubella-II (MMR-II) vaccine in a randomly selected, population-based cohort of healthy children. We determined if a correlative and predictive intraclass relationship exists between CMI to the three components of MMR-II. We detected positive lymphoproliferative responses to measles, mumps, and rubella vaccines. Mumps vaccine used as an antigen had the highest median stimulation index followed by measles and rubella vaccines. The overall intraclass correlation value for lymphoproliferative response to measles, mumps, and rubella using Pearson's correlation was 0.61 (95% confidence interval = 0.56, 0.66). We observed a significant pairwise association to individual vaccine components between subjects in the upper and lower 10th percentile of immune response. This study demonstrates recall CMI post-MMR-II vaccination with significant intraclass correlation among the CMI responses to the three vaccine components.

Sero-epidemiology of measles and mumps in Korea: impact of the catch-up campaign on measles immunity

A catch-up campaign targeting children aged 8-16 years using measles-rubella (MR) vaccine was conducted during 2001 in Korea. To evaluate the impact of the campaign and assess mumps immunity, human IgG antibodies were detected using ELISA for measles (5826 samples) and mumps (5890 samples) in a national sample of opportunistically collected sera from a population aged 0-34 years. The measles immunity increased by 5-10% following the catch-up campaign in the targeted age group. Infants lost maternal antibodies rapidly and about 90% of infants were susceptible to measles and mumps at 6-8 months of life. The sero-prevalence of mumps antibody increased slowly with age and stabilized at a lower level when compared with that of measles. Despite an immediate reduction in susceptibility among the targeted age group of the catch-up campaign, continuous efforts to increase immunization coverage are needed to interrupt indigenous measles transmission. Furthermore, our results suggest continuous mumps outbreaks could occur because of the accumulation of susceptible individuals.

Molecular identification of mumps virus genotypes from clinical samples: standardized method of analysis

A sensitive nested reverse transcription-PCR assay, targeting a short fragment of the gene encoding the small hydrophobic protein (SH gene), was developed to allow rapid characterization of mumps virus in clinical samples. The sensitivity and specificity of the assay were established using representative genotypes A, B, C, D, E, and F. Mumps virus RNA was characterized directly from cerebrospinal fluid (CSF) samples and in extracts of mumps virus isolates from patients with various clinical syndromes. Direct sequencing of products and subsequent phylogenetic analysis enabled genetic classification. A simple web-based system of sequence analysis was established. The study also allowed characterization of mumps virus strains from Argentina as part of a new subgenotype. This PCR assay for characterization of mumps infections coupled to a web-based analytical program provides a rapid method for identification of known and novel strains.

Outbreak of mumps in a vaccinated child population: a question of vaccine failure?

In Belgium, children are immunized against measles-mumps-rubella (MMR) in a two-dose schedule at the age of 15 months and 11 years. Despite these recommendations, epidemics of mumps still occur. During an outbreak of mumps in Bruges (Belgium), 105 cases were registered in seven schools (age group 3-12 years). Lower than optimal vaccination coverage, inadequate vaccination schedule and a combination of primary and/or secondary vaccine failure are considered as possible reasons for the outbreak as described in the article. The role of secondary vaccine failure is highlighted.

Regional outbreak of mumps due to genotype H in Korea in 1999

Serological and virological studies were carried out of a mumps outbreak which occurred in one region, Yoeju County, Southeast of Seoul in Korea from September to December, 1999. Sera from 736 children at 8-13 years of age of patients with mumps and healthy children were tested for mumps-specific antibodies by enzyme immunoassay. The overall IgM positive rate was 7.6% (56/736), compared with 69.8% (514/736) for IgG. Of the 49 children with both IgG and IgM, 32 were also confirmed by both clinical and serological diagnosis. IgM antibodies were detected even in the samples collected up to 3 months after the onset of symptoms. Although 436 children had been vaccinated before the outbreak, 27 (6.2%) were found to be IgM positive, particularly 6 (4.4%) of 136 were positive serologically despite a second-dose vaccinees. Sequence analysis of the small hydrophobic (SH) gene of 4 mumps viruses isolated from 42 saliva specimens revealed that these were related to the genotype H, but distinguishable from European strains. This is the first study on the outbreak due to mumps virus genotype H and provides information to assess the understanding of recent outbreaks of mumps in Korea.

Comparison between indirect immunofluorescence assay and shell vial culture for detection of mumps virus from clinical samples

We report a prospective comparison of the efficacies of an indirect immunofluorescence assay (IFA) and shell vial culture (SVC) of throat swab and urine samples from patients with mumps. Throat swab samples were used for the IFA; the urine samples and throat swabs were inoculated into vials of Vero cells. We studied 62 patients by using 62 throat swabs and 50 urine samples (50 patients with both samples). Sixty (96.7%) throat samples were positive in the SVC, and 61 (98.3%) were positive in the IFA. For the 50 patients from whom both samples were available, the IFA was positive in 50 (100%) cases, the urine sample was positive in 49 (98%) cases, and the throat swab was positive in 48 (96%) cases (P > 0.05). This comparison of throat swabs and urine samples has shown that the two clinical samples are similar in efficacy.

Study of the immune response engendered by differents combined measles, mumps and rubella (MMR) vaccines in an area of Andalusia (Spain)

The objective of the study is to evaluate and compare the degree of serological protection conferred by the three components of two MMR vaccines: "Vac triple MSD" (Aventis Pasteur MSD) and "Triviraten" (Berna), and to study the effects of a second dose of "Priorix" (Glaxo SmithKline), in an unprotected population. In March 2001, this study was conducted in a sample of 86 children aged 3 and 4 years, in two Basic Health Zones of Cádiz (Spain). Mumps, measles and rubella antibody titers were evaluated by IgG enzyme linked immunosorbent assay (ELISA). All the children showing lack of response were revaccinated with the vaccine "Priorix" of GSK; in 12 of these children (all vaccinated previously with "Triviraten"), studies confirmed the existence of seroconversion utilizing the same methodology. The most outstanding finding has been the low percentage of children vaccinated with "Triviraten" possessing protective titers (>1:500) against mumps (14.3%) compared with those vaccinated with "Vac triple MSD" (81.1%, P<0.000001); geometric mean values (GMT) of 164 and 1631, respectively, were obtained. Significant differences, and in the same direction, were also found in respect of measles (83.7 and 100%, and GMT of 889 and 5076), although not so striking. However, all the children studied did have protective titres (>16UI/ml) of antibodies against rubella. Of the 12 children studied who had not responded with protective titers of anti-mumps antibodies, eight children (66.7%) showed seroconversion with "Priorix", and only one child (25%) presented seroconversion in the response to measles. We have thus proved that the "Rubini" strain provides insufficient protection against mumps in our child population. We have also found that the "Edmonston-Zagreb" strain confers less protection against measles than the "Enders" strain, although the "Schwarz" strain, after revaccination of the children who had failed with the "Edmonston-Zagreb" strain, did not achieve a satisfactory seroconversion, either.

Proposed criteria for classification of new genotypes of mumps virus

The nucleotide sequences of a 300 bp segment carrying the small hydrophobic (SH) protein gene of a large number of virus strains, belonging to 10 different mumps virus genotypes denoted A-J, were compared. When virus strains belonging to the same genotype were compared intra-genotypically, a variation in the range 2-4% was recorded. The level of inter-genotypical variation was higher (8-18%). A consistent finding was the more pronounced variation found when the A genotype was compared to the B-J genotypes than when the B-J genotypes were compared among themselves. A similar relatively more pronounced genetic variation between the A and B-D genotypes has also been found previously with the hemagglutinin-neuraminidase and fusion protein genes. It is concluded that the establishment of a new genotype should be founded on a nucleotide variation of the SH gene of > or = 6% in relation to previously described genotypes.

An outbreak of mumps in the metropolitan area of Walsall, UK

OBJECTIVE

To describe the epidemiology of excessive mumps cases during the year 2000, within the metropolitan area of Walsall, UK; to assess the impact of the mumps outbreak on morbidity; and to inform future communicable disease control strategy.

METHODS

Demographic records, school attendance, uptake of the measles-mumps-rubella (MMR) vaccine, and mumps-associated admission to hospital, were reviewed for all Walsall residents diagnosed and notified with mumps during the year 2000.

RESULTS

There were 200 mumps notifications in 2000 (76.6 per 100,000), representing the highest incidence in England. Only 91 of the notified cases were salivary antibody positive for mumps IgM, and 32 were negative, although 77 were not tested. Since 1990, annual totals have never previously exceeded 20. Over 90% of patients were <20 years old, with a peak age group of 10-14 years; 88% attended schools located within Walsall. The pattern of spread suggested that the outbreak proceeded through schools from north to south in the more deprived western half of the metropolitan area. Most cases (136, 68%) had received one (99, 49.5%) or two (37, 18.5%) doses of MMR vaccine; cases > or =20 years old had never received MMR. Six cases (aged 4-14 years) were admitted to hospital, all with a successful outcome, including one male with meningitis and one female with pancreatitis. Current uptake of the MMR vaccine at 24 months has dropped to below 90% in recent years, as in most parts of the UK.

CONCLUSIONS

Future mumps outbreaks in schools, and among older age groups, can be predicted, since most older children and young adults have received only one dose of MMR vaccine or no vaccination at all. Primary vaccine failure is well described in mumps, and cases during outbreaks can include recipients of two MMR vaccine doses. It was fortunate that no severe morbidity was associated with this outbreak (prior to MMR, two to four mumps deaths occurred annually in England and Wales). Measures to restore the uptake of MMR to the previous levels of above 90-95% will be necessary to reduce the risk of the mumps virus circulating within communities. Older children are susceptible, and it may be advisable to ensure second-dose MMR uptake while they are still at or when they leave school, or when they enter college, university or the military.

Mumps: immune status of adults and epidemiology as a necessary background for choice of vaccination strategy in Jordan

The prevalence of antibodies against mumps in 333 students at Jordan University was assessed using the ELISA technique. Most of the students (93.7%) were seropositive for mumps. About 50% of unvaccinated students and students vaccinated using the optional single-dose MMR vaccine had mumps. The incidence rate of mumps in different age groups and sexes, the geographic distribution and the seasonality of mumps infection prior to the adoption of compulsory MMR vaccination were investigated during the period from 1988 to 2000. Mumps occurred in all age groups in both sexes and the incidence rate was higher in children aged 5-14 years than in adults. There was a higher frequency in winter and spring with epidemic peaks in 1988, 1993 and 2000. Southern Jordan had the highest incidence rate due to low vaccination coverage by the private clinics. The data support the introduction of compulsory MMR vaccination in Jordan for all susceptible individuals. Evaluation of the effectiveness of the compulsory single-dose vaccine and, based on the outcome, a second dose of this vaccine is also recommended in order to achieve and maintain a high level of immunization.

Evaluation of different continuous cell lines in the isolation of mumps virus by the shell vial method from clinical samples

AIMS

To compare prospectively the efficacy of the Vero, LLC-MK2, MDCK, Hep-2, and MRC-5 cell lines in the isolation of the mumps virus from clinical samples by means of the shell vial method.

METHODS

During an epidemic outbreak of parotiditis 48 clinical samples (saliva swabs and CSF) were studied. Two vials of the Vero, LLC-MK2, MDCK, MRC-5, and Hep-2 cell lines were inoculated with 0.2 ml of the samples by the shell vial assay. The vials were incubated at 36 degrees C for two and five days. The vials were then fixed with acetone at -20 degrees C for 10 minutes and stained by a monoclonal antibody against mumps virus by means of an indirect immunofluorescence assay.

RESULTS

The mumps virus was isolated from 36 samples. The Vero and LLC-MK2 cell lines showed a 100% isolation capacity, MDCK showed 77.7%, MRC-5 showed 44.4%, and Hep-2 showed 22.2%. The Vero and LLC-MK2 lines were significantly different to the other cell lines (p < 0.001). The sensitivity for the Vero and LLC-MK2 lines at two and five days of incubation was identical (100%). The values obtained in the study of the quantitative isolation capacity (positive isolation with > 5 infectious foci) were 94.4% for Vero, 97.2% for LLC-MK2, 5.5% for MDCK, 5.5% for Hep-2, and 0% for MRC-5.

CONCLUSIONS

The Vero and LLC-MK2 cell lines are equally efficient at two and five days incubation for the isolation of the mumps virus from clinical samples, and the use of the shell vial method considerably shortens the time of aetiological diagnosis with higher specificity.

Characterization of two decades of temporal co-circulation of four mumps virus genotypes in Denmark: identification of a new genotype

Twenty-nine Danish virus isolates and 14 serum samples from patients with mumps were genotyped by nucleotide sequencing of the small hydrophobic (SH) protein gene and the deduced 57 amino acid sequences were aligned with sequences of mumps virus strains published previously. Four neurovirulent genotypes of the SH protein gene, genotypes C, D, H and a new genotype, designated J, were found. There was a dynamic fluctuation of the different genotypes over the two decade period of time. Genotype J was found from 1981 to 1988; genotypes C and H exhibited a similar distribution in time. Genotype D was found between 1979 and 1982, it then disappeared and reappeared again in 1996. From 1996 onwards, genotype D was found to be the predominant genotype, which is in contrast to the situation seen in the neighbouring country of Sweden, where, since 1985, only genotype A has been found.

Rubella susceptibility predicts measles susceptibility: implications for postpartum immunization

Measles and mumps antibody titers were measured in 262 pregnant women who were either positive (n=128) or negative (n=134) for rubella antibodies. Susceptibility to measles and mumps was detected in 4.6% (12/262) and 7.6% (14/184) of the women, respectively. Of the rubella-susceptible group, 8.2% were also measles susceptible, whereas only 0.8% of the rubella-immune women were measles susceptible. Susceptibility to mumps was evenly divided between rubella-susceptible (7.8%) and rubella-immune (7.4%) groups.

Intranasal immunization with mumps virus DNA vaccine delivered by influenza virosomes elicits mucosal and systemic immunity

To improve the efficiency of liposome-mediated DNA transfer as a tool for gene therapy or vaccinology, we have further developed a new delivery system based on the modified immunopotentiating reconstituted influenza virus (IRIV). In this study, we engineered a plasmid DNA vector expressing the mumps virus hemagglutinin or the fusion protein. The administration of this DNA vaccine delivered by influenza virosomes, in combination with the mucosal adjuvant Escheriagen via the intranasal route, was efficient for inducing an immune response, both mucosally and systemically, in mice. The production of IgG2a mumps virus-specific antibodies and the secretion of interleukin 10 (IL-10) by antigen-specific T cells indicated that not only Th1 but also Th2 responses were induced by this DNA vaccine formulation. These results suggest that cationic virosomes in combination with Escheriagen may have great potential as an efficient delivery system for intranasal DNA immunization and provide an immune barrier at the mucosal sites.

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.

Immune response after primary and re-vaccination with different combined vaccines against measles, mumps, rubella

The humoral immune response after primary and re-vaccination confirmed the high immunogenicity of the combined vaccines used: "MMR-Vax(R)", "Pluserix(R)" and "Triviraten(R)". The investigation of paired serum samples of prevaccinal seronegative infants (n90-100% for all three components with the exception of the mumps component of "Triviraten(R)" (38%). However, by additional methods (plaque neutralisation test, immunofluorescence test) mumps antibodies could be detected in 93.4% of infants having received vaccine "Triviraten(R)". The mean values of antibody activities against the three components did not differ significantly after vaccination with "MMR-Vax(R)" and "Pluserix(R)". However, after vaccination with "Triviraten(R)" the mean antibody values were significantly lower (P<0.01) against the measles strain "Edmonston-Zagreb" and especially lower (2-20 times) against the mumps virus strain "Rubini". Revaccination of pre-vaccinal seropositive schoolchildren and adolescents (n=676) with "MMR-Vax(R)" and "Pluserix(R)" produced no different results. The rate of vaccinees responding with a booster reaction reached 68.4% for measles and mumps, but only 8.6% for rubella. A booster reaction could be observed in 100% of those vaccinees who had antibodies at a low level, also in the case of naturally acquired immunity. The low-level range for antibodies against measles was defined as 0.15<0. 40 IU/ml, mumps 1:230</=1:500 and rubella 7-16 IU/ml. The rate of vaccinees with low-level antibodies against measles can become as high as 10%, for mumps 20% and for rubella 3%. The correlation between the level of antibodies and protection against the disease is discussed. The rate of individuals in a population with doubtful protection (unvaccinated, non-responder and low responder after primary vaccination) prevents to reach the herd immunity of 95% necessary for elimination. The results of our serological studies strongly recommend re-vaccination against measles, mumps and rubella.

Nested PCR for rapid detection of mumps virus in cerebrospinal fluid from patients with neurological diseases

In this study, we have developed a reverse transcription (RT)-nested polymerase chain reaction (n-PCR) for the detection of mumps virus RNA in cerebrospinal fluid (CSF) from patients with neurological infections. A specific 112-bp fragment was amplified by this method with primers from the nucleoprotein of the mumps virus genome. The mumps virus RT-n-PCR was capable of detecting 0.001 PFU/ml and 0.005 50% tissue culture infective dose/ml. This method was found to be specific, since no PCR product was detected in each of the CSF samples from patients with proven non-mumps virus-related meningitis or encephalitis. Mumps virus RNA was detected in all 18 CSF samples confirmed by culture to be infected with mumps virus. Positive PCR results were obtained for the CSF of 26 of 28 patients that were positive for signs of mumps virus infection (i.e., cultivable virus from urine or oropharyngeal samples or positivity for anti-mumps virus immunoglobulin M) but without cultivable virus in their CSF. Overall, mumps virus RNA was detected in CSF of 96% of the patients with a clinical diagnosis of viral central nervous system (CNS) disease and confirmed mumps virus infection, while mumps virus was isolated in CSF of only 39% of the patients. Furthermore, in a retrospective study, we were able to detect mumps virus RNA in 25 of 55 (46%) CSF samples from patients with a clinical diagnosis of viral CNS disease and negative laboratory evidence of viral infection including mumps virus infection. The 25 patients represent 12% of the 236 patients who had a clinical diagnosis of viral CNS infections and whose CSF was examined at our laboratory for a 2-year period. The findings confirm the importance of mumps virus as a causative agent of CNS infections in countries with low vaccine coverage rates. In summary, our study demonstrates the usefulness of the mumps virus RT-n-PCR for the diagnosis of mumps virus CNS disease and suggests that this assay may soon become the "gold standard" test for the diagnosis of mumps virus CNS infection.

The control of mumps in Israel

BACKGROUND

Measles-mumps-rubella (MMR) vaccine replaced monovalent measles vaccine in the routine childhood vaccination schedule in Israel in December 1988, primarily to achieve the elimination of the congenital rubella syndrome. In this observational study, we report on changes in reported mumps incidence in Israel from the time of the introduction of MMR vaccine until the end of 1998.

METHODS

The report is based upon passive national surveillance of mumps incidence, which has been notifiable in Israel since 1977.

RESULTS

Reported mumps incidence in Israel is now less than 2% the pre-vaccine incidence.

CONCLUSIONS

In the decade since the introduction of routine mumps vaccination in 1-year-olds in Israel, mumps control has been achieved. Although small outbreaks occur and may continue to occur in future years, because of under-vaccination of children, primary vaccine failure and waning immunity, it can tentatively be said that mumps is no longer a public health problem in Israel.

An outbreak of mumps among young adults in Vancouver, British Columbia, associated with 'rave' parties

In early 1997 an unexpectedly high number of cases of mumps was reported in Vancouver, British Columbia.

METHODS

A case control study was conducted to address four objectives: 1) Describe the outbreak and the population at risk, 2) examine the impact of mumps on this population, 3) identify personal risk factors for infection, and 4) test the hypothesis that social gatherings, 'rave' parties in particular, were a risk factor in this outbreak.

RESULTS

Mumps infection was associated with: attending a rave party [OR = 17; 95% CI: 2.7-710], residing in Vancouver [OR = 3.7; 95% CI: 1.4-10], and contact with a person with mumps [OR = 13; 95% CI: 2-552], during the 'exposure' period. Vaccine effectiveness, ascertained by self-reported immunization status, was 80% [95% CI: 29%-96%].

CONCLUSIONS

Attendance at rave parties was associated with mumps infection during this outbreak. Many persons aged 17-40 may remain susceptible to mumps; in BC these persons are eligible for one dose of MMR and should be encouraged to be vaccinated.

Response to measles revaccination among toddlers in Saudi Arabia by the use of two different trivalent measles-mumps-rubella vaccines

This trial confirmed the immunogenicity of a standard dose of measles vaccine Edmonston-Zagreb strain administered at the age of 6 months as evaluated serologically at 12 months of age in 94 healthy children in Saudi Arabia. The residual seropositivity rate for measles was 53.4 and 80.6% as measured by enzyme immunoassay (EIA) and plaque neutralization, respectively, and could be increased to virtually 100% seroprotection after immunization with 1 of 2 measles-mumps-rubella (MMR) vaccines (Triviraten Berna or MMR II MSD) at 12 months of age. In both groups, more than 90% of infants showed an immune response to the mumps and rubella vaccine strains at 14 months of age. There was a difference in the geometric mean titres of mumps antibodies in favour of MMR II (P < 0.001). The seroconversion rates for mumps antibodies differed between the 2 vaccines because of the different test systems and/or the different cut-off levels used. The study reconfirmed that for the assessment of Rubini mumps vaccine-induced antibodies the indirect immunofluorescence test is superior to the EIA. The systemic tolerability of both vaccines was excellent. Triviraten Berna is exclusively propagated on human diploid cell cultures and hence free of avian proteins.

Analysis of mumps vaccine failure by means of avidity testing for mumps virus-specific immunoglobulin G

To characterize patients with mumps vaccine failure, avidity testing was performed with the Enzygnost Anti-Parotitis Virus/IgG kit using a single-dilution-6 M urea denaturation method. Five groups of patients were tested. Group 1 consisted of 29 patients with primary mumps infections; group 2 was 20 children and adults with a definite history of natural infection; group 3 was 7 patients with a recent mumps vaccination, 1 of whom developed parotid gland swelling and aseptic meningitis; group 4 was 14 patients with mumps vaccine failure; and group 5 was 6 patients with recurrent episodes of parotitis in addition to a history of vaccination. On the basis of the results of groups 1 and 2, an avidity of </=31% was determined to be low, and >/=32% was determined to be high. Avidity maturation from low to high appears to occur around 180 days after the acute illness. The results of group 3 showed that the vaccine-induced immunoglobulin G (IgG) had very low avidity. Among the 14 patients in group 4, 12 patients, including 7 with a positive IgM response, were diagnosed as having secondary vaccine failures. The results of group 5 suggested the possibility that the avidity of the mumps vaccine-induced IgG remains low or borderline. These results showed that secondary mumps vaccine failure occurs not infrequently, even among school age children under condition in which the vaccine coverage is low (i.e., 33% in our study population), and therefore, vaccinees are prone to be exposed to wild-type viruses. Avidity testing should provide information useful for the analysis of mumps virus infections.

Comparison of the neurovirulence of a vaccine and a wild-type mumps virus strain in the developing rat brain

Prior to the adoption of widespread vaccination programs, mumps virus was the leading cause of virus-induced central nervous system (CNS) disease. Mumps virus-associated CNS complications in vaccinees continue to be reported; outside the United States, some of these complications have been attributed to vaccination with insufficiently attenuated neurovirulent vaccine strains. The development of potentially neurovirulent, live, attenuated mumps virus vaccines stems largely from the lack of an animal model that can reliably predict the neurovirulence of mumps virus vaccine candidates in humans. The lack of an effective safety test with which to measure mumps virus neurovirulence has also hindered analysis of the neuropathogenesis of mumps virus infection and the identification of molecular determinants of neurovirulence. In this report we show, for the first time, that mumps virus infection of the neonatal rat leads to developmental abnormalities in the cerebellum due to cerebellar granule cell migration defects. The incidence of the cerebellar abnormalities and other neuropathological and clinical outcomes of mumps virus infection of the neonatal rat brain demonstrated the ability of this model to distinguish neurovirulent (Kilham) from nonneurovirulent (Jeryl Lynn) mumps virus strains. Thus, this neonatal rat model may prove useful in evaluating the neurovirulence potential of new live, attenuated vaccine strains and may also be of value in elucidating the molecular basis of mumps virus neurovirulence.

Detection of mumps virus in clinical specimens by rapid centrifugation culture and conventional tube cell culture

Conventional tube cell culture was compared with a 2 day and 5 day spin-amplified shell vial indirect immunofluorescence assay for the detection of mumps virus in swabs from the area of Stensen's duct. The sensitivity and specificity of the shell vial assay were 95.9 and 100%, respectively. The shell vial detected 66.3% of the positive cultures within 2 days of inoculation while the first positive results were available by conventional tube cell culture after 3 days (1.6%) reaching 72.4% of all culture positive specimens after 7 days. These data suggest that a centrifugation shell vial indirect immunofluorescence assay may be useful for rapid detection of mumps virus in clinical specimens.

Comparative study of reactogenicity and immunogenicity of new and established measles, mumps and rubella vaccines in healthy children

Concerns about the association of aseptic meningitis with measles-mumps-rubella (MMR) vaccines containing the Urabe Am 9 strain and the increasing worldwide demand for MMR vaccines, prompted the development of a new mumps vaccine strain (RIT 4385) by SmithKline Beecham Biologicals (SB) as part of a trivalent live attenuated MMR vaccine. The present study assessed the immunogenicity and reactogenicity of two lots of 'Priorix' with a widely used and established vaccine M-M-R II (Merck & Co. Inc.) as comparator vaccine. 255 healthy children, 12 to 24 months of age, were enrolled in a single-blind study and randomly allocated to receive a single dose of one of two lots of "Priorix" or M-M-R II vaccine. Vaccinees were followed up for six weeks post-vaccination for solicited and unsolicited symptoms. Immunogenicity was determined in pre- and 60 days post-vaccination sera using commercial immunoassays for measles, mumps and rubella antibodies. There were no significant differences in immune responses between groups for any of the three vaccine components. In initially seronegative subjects, the respective post-vaccination seroconversion rates for 'Priorix' lots 1 and 2, and M-M-R II were 100, 100 and 97.6% for measles antibodies, 91.7, 95.1 and 94% for mumps antibodies and 100, 100 and 100% for rubella antibodies, respectively. GMTs for the three groups were 3,076, 3,641 and 3,173 mIU/ml for measles antibodies, 934, 900 and 1,043 U/ml for mumps antibodies, and 86.4, 87.5 and 97.1 IU/ml for rubella antibodies, respectively. The incidence of local symptoms was significantly lower for both 'Priorix' lots (17.6 and 15.3% for lots 1 and 2, respectively) than for M-M-R II (37.6%). Fever > or = 38.1 degrees C during the six-week observation period occurred in approximately 25% of all subjects in all groups with no differences between the groups. No parotid/salivary gland swelling or signs of suspected meningism were reported, and there were no serious adverse events related to vaccination. The new MMR vaccine 'Priorix' containing the new RIT 4385 mumps strain was safe and had a significantly improved local tolerability profile over the comparator vaccine, M-M-R II, while eliciting an at least equivalent immune response.

Immunity to mumps before and after MMR vaccination at 12 years of age in the first generation offered the two-dose immunization programme

Sweden was the first country in the world to introduce a two-dose programme of vaccination against measles, mumps and rubella with a combined vaccine (MMR). It was commenced in 1982 and the vaccination was carried out at the ages of 18 months and 12 years. In 1992-93 the first age-group vaccinated at 18 months reached the age of 12 and accordingly received a second dose of MMR. A total of 382 children participated in the present study. Sero-immunity against mumps was studied by testing neutralizing antibodies using serial dilutions inoculated into cell cultures before and after the 12-year vaccination. Of the 229 children earlier vaccinated (group A), 27% lacked demonstrable antibodies before the booster. Of those without documented vaccination records (group B), 56% were seronegative before vaccination. After vaccination, 93% of group A and 86% of group B were seropositive (titre > or = 2). In the seronegative children, whether vaccinated earlier or not, the seroconversion was ca 75%. Previously unvaccinated children positive before vaccination and thus likely to be naturally immune had a higher mean-titre both before and after vaccination than the seropositive children earlier vaccinated. So far, the two-dose programme has proceeded as expected.

Wild type mumps viruses circulating in China establish a new genotype

By analysing the nucleotide sequence of the SH genes of five mumps virus strains derived from the clinical specimens collected during the 1995/96 mumps epidemic in China a new genotype has been established. The circulating viruses showed divergence ranging from 0.8-4.5% at the nucleotide level and 3.5-12.3% at the amino acid level. In addition, a more rational approach has been taken in proposing genotype groupings to MuV strains.

Safety and characterization of the immune response engendered by two combined measles, mumps and rubella vaccines

We performed a randomized trial to compare the safety and immunogenicity of two combined measles, mumps and rubella vaccines in healthy children 14-24 months of age. Triviraten Berna Vaccine (Swiss Serum and Vaccine Institute), contains the Edmonston Zagreb 19 strain of measles virus, the Rubini mumps virus strain and the Wistar RA 27/3 rubella strain while MMR-Vax (Merck, Sharp & Dohme, West Point, PA) contains the Enders attenuated Edmonston measles strain, the Jeryl Lynn mumps strain and the Wistar RA 27/3 rubella strain. Immunization with Triviraten Berna was associated with a significantly lower incidence of swelling and redness at the injection site in addition to a reduced rate of fever compared with MMR-Vax. Seroconversion rates for the measles and rubella vaccine components were comparable in all tests used. However, seroconversion for the mumps vaccine component was test-dependent. Using an ELISA, the seroconversion rate following immunization with MMR-Vax was significantly (P < 0.01) higher than for Triviraten Berna. In contrast, nearly identical rates were obtained using an indirect immunofluorescence test. Both vaccines were equally effective at engendering antibodies capable of neutralizing wild type mumps virus. Geometric mean ELISA antibody titers against measles and mumps virus were higher following immunization with MMR-Vax while that for rubella was higher after immunization with Triviraten Berna. A small number (N = 13) of adolescents immunized either with MMR-Vax or Triviraten Berna were reimmunized with Triviraten Berna and various humoral and cellular response parameters to the measles and mumps vaccine components analyzed. While few subjects mounted a humoral antibody response to measles, most likely due to elevated baseline titers, there was a marked lymphoproliferative response. Anti-mumps virus ELISA antibody titers were higher both at baseline and after reimmunization in subjects who received MMR-Vax for primary immunization. However, there was no difference in either neutralizing titer or proliferative response in subjects primed with MMR-Vax or Triviraten Berna either before or after reimmunization.

RT-PCR based diagnosis and molecular characterisation of mumps viruses derived from clinical specimens collected during the 1996 mumps outbreak in Portugal

Clinical specimens collected during an outbreak of mumps were characterised by RT-PCR, nested PCR, and nucleotide sequencing. Mumps virus was positively identified in 12/21(57%) saliva, 9/21(43%), throat and 1/33(3%) urine specimens and further sequence comparison revealed that at least six strains of viruses, which differed from 0-9.43% at the nucleotide levels, were cocirculating during the epidemic. However, phylogenetic analysis showed that these viruses grouped with two previously identified lineages which were mostly composed of other European mumps virus isolates.

Antibody persistence after primary measles-mumps-rubella vaccine and response to a second dose given at four to six vs. eleven to thirteen years

BACKGROUND

Since 1989 the American Academy of Pediatrics and the ACIP have recommended a second dose of measles-mumps-rubella vaccine (M-M-R-II) at either school entry or age 11 to 13 years. Unfortunately few studies are available to compare responses to vaccine at the two ages. We performed a prospective trial to determine the persistence of antibody to measles, mumps and rubella vaccination in two age groups and the response to a second dose given at either 4 to 6 or 11 to 13 years.

METHODS

Thirty-eight children 4 to 6 years old and 57 children 11 to 13 years old were given a second dose of M-M-R-II as they presented for yearly examinations. All had received the first dose at > or = 15 months of age. Measles and rubella antibody were measured by enzyme-linked immunosorbent assay (ELISA) and neutralizing antibody (NT) assay, and mumps antibody was measured by an ELISA method only. An IgM-ELISA antibody assay for measles was used in selected children. Prevaccination and 3- to 4-week post-vaccination sera were obtained. Measles ELISA, measles-neutralizing antibody (NT) and rubella-neutralizing antibody (NT) assays were performed in all children. Seventy-nine of the 95 children had sufficient sera for repeat measles tests, as well as mumps and rubella ELISA determinations.

RESULTS

Before the second dose ELISA seropositivity rates for measles and mumps were not significantly different between the two groups. Rubella ELISA seropositivity was 67% in 11- to 13-year-olds, compared with 90% in 4- to 6-year-olds (P < 0.01), suggestive of waning immunity. Rubella NT seropositivity was also lower in 11- to 13-year-olds than in 4- to 6-year-olds (63% vs. 100%, P < 0.01). After revaccination, 100% of the children become seropositive for all 3 antibodies. We performed measles IgM-ELISA testing on all 17 measles-seronegative children, as well as 15 seropositive children and 19 children who were 1 month postvaccination with the first M-M-R-II at 15 months. The purpose was to determine whether the seronegative children were primary or secondary failures. Five of the 17 children with undetectable pre-second dose antibody made IgM measles antibody after revaccination, suggesting that they were primary vaccine failures.

CONCLUSIONS

Because all children became seropositive after revaccination, the age of administration can be based on the convenience of vaccine scheduling. However, in view of the apparent decline in rubella antibodies at 11 to 13 years, future studies of rubella vaccination should address the issue of whether earlier boosting leads to greater susceptibility at the time of reproductive age.