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

The High Seropositivity of Mumps Virus IgG Antibodies among School-Aged Children in Rural Areas of the Mbarali District in the Mbeya Region, Tanzania: It Is High Time for Consideration in the National Immunization Program

Mumps is an acute contagious viral disease caused by paramyxovirus characterized by complications that include orchitis, oophoritis, aseptic meningitis, and spontaneous abortion among many others. This study reports high mumps IgG seropositivity among school-aged children in rural areas of the Mbeya region, information that might be useful in understanding the epidemiology of mumps and instituting appropriate control measures including vaccination. Between May and July 2023, a cross-sectional study involving 196 enrolled children aged 5-13 years was conducted. Sociodemographic information and other relevant information were collected using a structured data collection tool. Blood samples were collected and used to detect mumps immunoglobulin G antibodies using indirect enzyme-linked immunosorbent assay (ELISA). A descriptive analysis was performed using STATA version 15. The median age of the enrolled children was 13 (interquartile range (IQR): 8-13) years. The seropositivity of mumps IgG antibodies was 88.8% (174/196, 95% CI: 83.5-92.5). By multivariable logistic regression analysis, history of fever (OR: 5.36, 95% CI: 1.02-28.22, p = 0.047) and sharing utensils (OR: 8.05, 95% CI: 1.99-32.65, p = 0.003) independently predicted mumps IgG seropositivity. More than three-quarters of school-aged children in rural areas of the Mbeya region are mumps IgG-seropositive, which is significantly associated with the sharing of utensils and history of fever. This suggests that the virus is endemic in this region, which calls for further studies across the country so as to institute evidence-based, appropriate control measures including a vaccination program.

Genome-wide determinants of cellular immune responses to mumps vaccine

BACKGROUND

We have previously described genetic polymorphisms in candidate genes that are associated with inter-individual variations in antibody responses to mumps vaccination. To expand upon our previous work, we performed a genome-wide association study (GWAS) to discover host genetic variants associated with mumps vaccine-induced cellular immune responses.

METHODS

We performed a GWAS of mumps-specific immune response outcomes (11 secreted cytokines/chemokines) in a cohort of 1,406 subjects.

RESULTS

Among the 11 cytokine/chemokines we studied, four (IFN-γ, IL-2, IL-1β, and TNFα) demonstrated GWAS signals reaching genome-wide significance (p < 5 × 10-8). A genomic region (encoding Sialic acid-binding immunoglobulin-type lectins/SIGLEC) located on chromosome 19q13 (p < 5 × 10-8) was associated with both IL-1β and TNFα responses. The SIGLEC5/SIGLEC14 region contained 11 statistically significant single nucleotide polymorphisms (SNPs), including the intronic SIGLEC5 rs872629 (p = 1.3E-11) and rs1106476 (p = 1.32E-11) whose alternate alleles were significantly associated with decreased levels of mumps-specific IL-1β (rs872629, p = 1.77E-09; rs1106476, p = 1.78E-09) and TNFα (rs872629, p = 1.3E-11; rs1106476, p = 1.32E-11) production.

CONCLUSIONS

Our results suggest that SNPs in the SIGLEC5/SIGLEC14 genes play a role in cellular and inflammatory immune responses to mumps vaccination. These findings motivate further research into the functional roles of SIGLEC genes in the regulation of mumps vaccine-induced immunity.

Genome-Wide Determinants of Cellular Immune Responses to Mumps Vaccine

Background

We have previously described genetic polymorphisms in candidate genes that are associated with inter-individual variations in antibody responses to mumps vaccination. To expand upon our previous work, we performed a genome-wide association study (GWAS) to discover host genetic variants associated with mumps vaccine-induced cellular immune responses.

Methods

We performed a GWAS of mumps-specific immune response outcomes (11 secreted cytokines/chemokines) in a cohort of 1,406 subjects.

Results

Among the 11 cytokine/chemokines we studied, four (IFN-γ, IL-2, IL-1β, and TNFα) demonstrated GWAS signals reaching genome-wide significance (p<5 x 10 -8 ). A genomic region (encoding Sialic acid-binding immunoglobulin-type lectins/SIGLEC) located on chromosome 19q13 (p<5×10 -8 ) was associated with both IL-1β and TNFα responses. The SIGLEC5/SIGLEC14 region contained 11 statistically significant single nucleotide polymorphisms (SNPs), including the intronic SIGLEC5 rs872629 (p=1.3E-11) and rs1106476 (p=1.32E-11) whose alternate alleles were significantly associated with decreased levels of mumps-specific IL-1β (rs872629, p=1.77E-09; rs1106476, p=1.78E-09) and TNFα (rs872629, p=1.3E-11; rs1106476, p=1.32E-11) production.

Conclusions

Our results suggest that SNPs in the SIGLEC5/SIGLEC14 genes play a role in cellular and inflammatory immune responses to mumps vaccination. These findings motivate further research into the functional roles of SIGLEC genes in the regulation of mumps vaccine-induced immunity.

Vaccines for measles, mumps, rubella, and varicella in children

BACKGROUND

Measles, mumps, rubella, and varicella (chickenpox) are serious diseases that can lead to serious complications, disability, and death. However, public debate over the safety of the trivalent MMR vaccine and the resultant drop in vaccination coverage in several countries persists, despite its almost universal use and accepted effectiveness. This is an update of a review published in 2005 and updated in 2012.

OBJECTIVES

To assess the effectiveness, safety, and long- and short-term adverse effects associated with the trivalent vaccine, containing measles, rubella, mumps strains (MMR), or concurrent administration of MMR vaccine and varicella vaccine (MMR+V), or tetravalent vaccine containing measles, rubella, mumps, and varicella strains (MMRV), given to children aged up to 15 years.

SEARCH METHODS

We searched the Cochrane Central Register of Controlled Trials (CENTRAL) (the Cochrane Library 2019, Issue 5), which includes the Cochrane Acute Respiratory Infections Group's Specialised Register, MEDLINE (1966 to 2 May 2019), Embase (1974 to 2 May 2019), the WHO International Clinical Trials Registry Platform (2 May 2019), and ClinicalTrials.gov (2 May 2019).

SELECTION CRITERIA

We included randomised controlled trials (RCTs), controlled clinical trials (CCTs), prospective and retrospective cohort studies (PCS/RCS), case-control studies (CCS), interrupted time-series (ITS) studies, case cross-over (CCO) studies, case-only ecological method (COEM) studies, self-controlled case series (SCCS) studies, person-time cohort (PTC) studies, and case-coverage design/screening methods (CCD/SM) studies, assessing any combined MMR or MMRV / MMR+V vaccine given in any dose, preparation or time schedule compared with no intervention or placebo, on healthy children up to 15 years of age.

DATA COLLECTION AND ANALYSIS

Two review authors independently extracted data and assessed the methodological quality of the included studies. We grouped studies for quantitative analysis according to study design, vaccine type (MMR, MMRV, MMR+V), virus strain, and study settings. Outcomes of interest were cases of measles, mumps, rubella, and varicella, and harms. Certainty of evidence of was rated using GRADE.

MAIN RESULTS

We included 138 studies (23,480,668 participants). Fifty-one studies (10,248,159 children) assessed vaccine effectiveness and 87 studies (13,232,509 children) assessed the association between vaccines and a variety of harms. We included 74 new studies to this 2019 version of the review. Effectiveness Vaccine effectiveness in preventing measles was 95% after one dose (relative risk (RR) 0.05, 95% CI 0.02 to 0.13; 7 cohort studies; 12,039 children; moderate certainty evidence) and 96% after two doses (RR 0.04, 95% CI 0.01 to 0.28; 5 cohort studies; 21,604 children; moderate certainty evidence). The effectiveness in preventing cases among household contacts or preventing transmission to others the children were in contact with after one dose was 81% (RR 0.19, 95% CI 0.04 to 0.89; 3 cohort studies; 151 children; low certainty evidence), after two doses 85% (RR 0.15, 95% CI 0.03 to 0.75; 3 cohort studies; 378 children; low certainty evidence), and after three doses was 96% (RR 0.04, 95% CI 0.01 to 0.23; 2 cohort studies; 151 children; low certainty evidence). The effectiveness (at least one dose) in preventing measles after exposure (post-exposure prophylaxis) was 74% (RR 0.26, 95% CI 0.14 to 0.50; 2 cohort studies; 283 children; low certainty evidence). The effectiveness of Jeryl Lynn containing MMR vaccine in preventing mumps was 72% after one dose (RR 0.24, 95% CI 0.08 to 0.76; 6 cohort studies; 9915 children; moderate certainty evidence), 86% after two doses (RR 0.12, 95% CI 0.04 to 0.35; 5 cohort studies; 7792 children; moderate certainty evidence). Effectiveness in preventing cases among household contacts was 74% (RR 0.26, 95% CI 0.13 to 0.49; 3 cohort studies; 1036 children; moderate certainty evidence).  Vaccine effectiveness against rubella, using a vaccine with the BRD2 strain which is only used in China, is 89% (RR 0.11, 95% CI 0.03 to 0.42; 1 cohort study; 1621 children; moderate certainty evidence).  Vaccine effectiveness against varicella (any severity) after two doses in children aged 11 to 22 months is 95% in a 10 years follow-up (rate ratio (rr) 0.05, 95% CI 0.03 to 0.08; 1 RCT; 2279 children; high certainty evidence). Safety There is evidence supporting an association between aseptic meningitis and MMR vaccines containing Urabe and Leningrad-Zagreb mumps strains, but no evidence supporting this association for MMR vaccines containing Jeryl Lynn mumps strains (rr 1.30, 95% CI 0.66 to 2.56; low certainty evidence). The analyses provide evidence supporting an association between MMR/MMR+V/MMRV vaccines (Jeryl Lynn strain) and febrile seizures. Febrile seizures normally occur in 2% to 4% of healthy children at least once before the age of 5. The attributable risk febrile seizures vaccine-induced is estimated to be from 1 per 1700 to 1 per 1150 administered doses. The analyses provide evidence supporting an association between MMR vaccination and idiopathic thrombocytopaenic purpura (ITP). However, the risk of ITP after vaccination is smaller than after natural infection with these viruses. Natural infection of ITP occur in 5 cases per 100,000 (1 case per 20,000) per year. The attributable risk is estimated about 1 case of ITP per 40,000 administered MMR doses. There is no evidence of an association between MMR immunisation and encephalitis or encephalopathy (rate ratio 0.90, 95% CI 0.50 to 1.61; 2 observational studies; 1,071,088 children; low certainty evidence), and autistic spectrum disorders (rate ratio 0.93, 95% CI 0.85 to 1.01; 2 observational studies; 1,194,764 children; moderate certainty). There is insufficient evidence to determine the association between MMR immunisation and inflammatory bowel disease (odds ratio 1.42, 95% CI 0.93 to 2.16; 3 observational studies; 409 cases and 1416 controls; moderate certainty evidence). Additionally, there is no evidence supporting an association between MMR immunisation and cognitive delay, type 1 diabetes, asthma, dermatitis/eczema, hay fever, leukaemia, multiple sclerosis, gait disturbance, and bacterial or viral infections.  AUTHORS' CONCLUSIONS: Existing evidence on the safety and effectiveness of MMR/MMRV vaccines support their use for mass immunisation. Campaigns aimed at global eradication should assess epidemiological and socioeconomic situations of the countries as well as the capacity to achieve high vaccination coverage. More evidence is needed to assess whether the protective effect of MMR/MMRV could wane with time since immunisation.

Estimating the Transmissibility of Mumps: A Modelling Study in Wuhan City, China

Despite the adoption of a national immunization program in China, the incidence of mumps remains high. This study aimed to describe the epidemiological characteristics, including the time, region, occupation, and age, of mumps in Wuhan from 2005 to 2018 and to evaluate its transmissibility. In this study, the susceptible-exposed-infectious-asymptomatic-recovered (SEIAR) model fitted the actual incidence data of mumps. The effective reproduction number (R t ) was used to evaluate and compare the transmission capacity in different areas. From 2005 to 2018, there were 36,415 cases. The incidence of mumps was highest among people aged 5-10 years (460.02 per 100,000). The SEIAR model fitted the reported mumps data well (P < 0.01). The median transmissibility (R t ) was 1.04 (range = 0-2.50). There were two peak spreads every year (from March to May and from October to December). The R t peak always appeared in the first 2 months of the peak incidence rate. The peak time of the epidemic spread of mumps was 1-2 months earlier than the peak incidence rate. The prevention and control measures of vaccination for children aged 5-10 years should be taken before the peak transmission capacity each year, 2 months before the peak of the outbreak, to reduce the spread of mumps.

Measles, mumps, rubella prevention: how can we do better?

INTRODUCTION

Measles, mumps, and rubella incidence decreased drastically following vaccination programs' implementation. However, measles and mumps' resurgence was recently reported, outbreaks still occur, and challenges remain to control these diseases.

AREAS COVERED

This qualitative narrative review provides an objective appraisal of the literature regarding current challenges in controlling measles, mumps, rubella infections, and interventions to address them.

EXPERT OPINION

While vaccines against measles, mumps, and rubella (including trivalent vaccines) are widely used and effective, challenges to control these diseases are mainly related to insufficient immunization coverage and changing vaccination needs owing to new global environment (e.g. traveling, migration, population density). By understanding disease transmission peculiarities by setting, initiatives are needed to optimize vaccination policies and increase vaccination coverage, which was further negatively impacted by COVID-19 pandemic. Also, awareness of the potential severity of infections and the role of vaccines should increase. Reminder systems, vaccination of disadvantaged, high-risk and difficult-to-reach populations, accessibility of vaccination, healthcare infrastructure, and vaccination services management should improve. Outbreak preparedness should be strengthened, including implementation of high-quality surveillance systems to monitor epidemiology. While the main focus should be on these public health initiatives to increase vaccination coverage, slightly more benefits could come from evolution of current vaccines.

Seroprevalence against the measles virus after vaccination or natural infection in an adult population in Madinah, Saudi Arabia

Background: Over the past few years, measles cases have increased worldwide, despite the availability of a safe and highly effective vaccine. Numerous countries have eliminated measles or have made substantial advancements toward elimination.Materials and Methods: This study investigated the seroprevalence of anti-measles antibodies and vaccination status among 362 men and 81 women in Madinah. All participants were vaccinated or acquired immunity naturally due to infection. We aimed to examine the persistence of anti-measles IgG antibodies, which were qualitatively and quantitatively determined using ELISA.Results: We showed that measles seropositivity (92%, n = 408) was significantly more frequent than negative (5.4%, n = 14) and equivocal results (2.5%, n = 11). Among men, 92.8% were seropositive for the anti-measles IgG antibody, whereas 88.9% of women were seropositive. In addition, a significant relationship was observed between age and measles seropositivity, with a significant positive correlation between age and anti-measles antibody concentration as assessed by Spearman's correlation analysis (r = 0.405, p < .001).Conclusion: Based on these results, observing the serological status of the population 20-38 y after vaccination may be necessary to minimize the proportion of individuals who may be vulnerable to contracting measles. Despite the efficacy of the measles, mumps, and rubella vaccine and the positive global impact associated with the use of this vaccine, including a general decline in measles cases, attention must still be paid to the issue of measles risk, and seronegative individuals should be identified and advised to receive a booster dose of the vaccine.

Epidemiological changes in mumps infections between 1990 and 2017 in urban area of Shanghai, China

2-dose measles-mumps-rubella (MMR) vaccine was recommended for children in Shanghai in November 1996 and incorporated into Shanghai immunization program in December 2008. We described the mumps epidemiology and assessed impact of the 2-dose MMR vaccination in Changning district, Shanghai, 1990–2017. We obtained the MMR vaccination coverage for children born during 1995–2015 and examined the incidence and disease characteristics of mumps during 1990–2017. The 1st dose MMR coverage had maintained above 95% since 1999 birth cohort. The 2nd dose MMR coverage reached above 90% since 2006 birth cohort. A total of 13,388 cases were reported during 1990–2017. The incidence decreased from 315.2 per 100,000 population in 1990 to 8.8 per 100,000 population in 2017. Of the 13,388 cases, 7585 (56.7%) were male and 91.7% were 1–14 years of age and 86.8% were children in kindergartens and students in schools. Compared with 1990–1996, the incidence had a significant decrease in 0–4 and ≥15 years in 1997–2008 and in all age groups in 2009–2017. A later birth cohort was associated with a lower incidence in children covered by MMR vaccination. In Conclusions, the incidence of mumps has dramatically declined with high coverage of 2-dose MMR in Changning district, Shanghai. Children in kindergartens and schools are still the most affected populations. An increase in incidence in adults has not occurred after 20 years of MMR vaccination. Long-term surveillance is needed to fully evaluate the impact of MMR vaccination policy.

Mumps Outbreaks in Vaccinated Populations-Is It Time to Re-assess the Clinical Efficacy of Vaccines?

History illustrates the remarkable public health impact of mass vaccination, by dramatically improving life expectancy and reducing the burden of infectious diseases and co-morbidities worldwide. It has been perceived that if an individual adhered to the MMR vaccine schedule that immunity to mumps virus (MuV) would be lifelong. Recent mumps outbreaks in individuals who had received two doses of the Measles Mumps Rubella (MMR) vaccine has challenged the efficacy of the MMR vaccine. However, clinical symptoms, complications, viral shedding and transmission associated with mumps infection has been shown to be reduced in vaccinated individuals, demonstrating a benefit of this vaccine. Therefore, the question of what constitutes a good mumps vaccine and how its impact is assessed in this modern era remains to be addressed. Epidemiology of the individuals most affected by the outbreaks (predominantly young adults) and variance in the circulating MuV genotype have been well-described alluding to a collection of influences such as vaccine hesitancy, heterogeneous vaccine uptake, primary, and/or secondary vaccine failures. This review aims to discuss in detail the interplay of factors thought to be contributing to the current mumps outbreaks seen in highly vaccinated populations. In addition, how mumps diagnoses has progressed and impacted the understanding of mumps infection since a mumps vaccine was first developed, the limitations of current laboratory tests in confirming protection in vaccinated individuals and how vaccine effectiveness is quantified are also considered. By highlighting knowledge gaps within this area, this state-of-the-art review proposes a change of perspective regarding the impact of a vaccine in a highly vaccinated population from a clinical, diagnostic and public perspective, highlighting a need for a paradigm shift on what is considered vaccine immunity.

Vaccines for measles, mumps, rubella, and varicella in children

BACKGROUND

Measles, mumps, rubella, and varicella (chickenpox) are serious diseases that can lead to serious complications, disability, and death. However, public debate over the safety of the trivalent MMR vaccine and the resultant drop in vaccination coverage in several countries persists, despite its almost universal use and accepted effectiveness. This is an update of a review published in 2005 and updated in 2012.

OBJECTIVES

To assess the effectiveness, safety, and long- and short-term adverse effects associated with the trivalent vaccine, containing measles, rubella, mumps strains (MMR), or concurrent administration of MMR vaccine and varicella vaccine (MMR+V), or tetravalent vaccine containing measles, rubella, mumps, and varicella strains (MMRV), given to children aged up to 15 years.

SEARCH METHODS

We searched the Cochrane Central Register of Controlled Trials (CENTRAL) (the Cochrane Library 2019, Issue 5), which includes the Cochrane Acute Respiratory Infections Group's Specialised Register, MEDLINE (1966 to 2 May 2019), Embase (1974 to 2 May 2019), the WHO International Clinical Trials Registry Platform (2 May 2019), and ClinicalTrials.gov (2 May 2019).

SELECTION CRITERIA

We included randomised controlled trials (RCTs), controlled clinical trials (CCTs), prospective and retrospective cohort studies (PCS/RCS), case-control studies (CCS), interrupted time-series (ITS) studies, case cross-over (CCO) studies, case-only ecological method (COEM) studies, self-controlled case series (SCCS) studies, person-time cohort (PTC) studies, and case-coverage design/screening methods (CCD/SM) studies, assessing any combined MMR or MMRV / MMR+V vaccine given in any dose, preparation or time schedule compared with no intervention or placebo, on healthy children up to 15 years of age.

DATA COLLECTION AND ANALYSIS

Two review authors independently extracted data and assessed the methodological quality of the included studies. We grouped studies for quantitative analysis according to study design, vaccine type (MMR, MMRV, MMR+V), virus strain, and study settings. Outcomes of interest were cases of measles, mumps, rubella, and varicella, and harms. Certainty of evidence of was rated using GRADE.

MAIN RESULTS

We included 138 studies (23,480,668 participants). Fifty-one studies (10,248,159 children) assessed vaccine effectiveness and 87 studies (13,232,509 children) assessed the association between vaccines and a variety of harms. We included 74 new studies to this 2019 version of the review. Effectiveness Vaccine effectiveness in preventing measles was 95% after one dose (relative risk (RR) 0.05, 95% CI 0.02 to 0.13; 7 cohort studies; 12,039 children; moderate certainty evidence) and 96% after two doses (RR 0.04, 95% CI 0.01 to 0.28; 5 cohort studies; 21,604 children; moderate certainty evidence). The effectiveness in preventing cases among household contacts or preventing transmission to others the children were in contact with after one dose was 81% (RR 0.19, 95% CI 0.04 to 0.89; 3 cohort studies; 151 children; low certainty evidence), after two doses 85% (RR 0.15, 95% CI 0.03 to 0.75; 3 cohort studies; 378 children; low certainty evidence), and after three doses was 96% (RR 0.04, 95% CI 0.01 to 0.23; 2 cohort studies; 151 children; low certainty evidence). The effectiveness (at least one dose) in preventing measles after exposure (post-exposure prophylaxis) was 74% (RR 0.26, 95% CI 0.14 to 0.50; 2 cohort studies; 283 children; low certainty evidence). The effectiveness of Jeryl Lynn containing MMR vaccine in preventing mumps was 72% after one dose (RR 0.24, 95% CI 0.08 to 0.76; 6 cohort studies; 9915 children; moderate certainty evidence), 86% after two doses (RR 0.12, 95% CI 0.04 to 0.35; 5 cohort studies; 7792 children; moderate certainty evidence). Effectiveness in preventing cases among household contacts was 74% (RR 0.26, 95% CI 0.13 to 0.49; 3 cohort studies; 1036 children; moderate certainty evidence). Vaccine effectiveness against rubella is 89% (RR 0.11, 95% CI 0.03 to 0.42; 1 cohort study; 1621 children; moderate certainty evidence). Vaccine effectiveness against varicella (any severity) after two doses in children aged 11 to 22 months is 95% in a 10 years follow-up (rate ratio (rr) 0.05, 95% CI 0.03 to 0.08; 1 RCT; 2279 children; high certainty evidence). Safety There is evidence supporting an association between aseptic meningitis and MMR vaccines containing Urabe and Leningrad-Zagreb mumps strains, but no evidence supporting this association for MMR vaccines containing Jeryl Lynn mumps strains (rr 1.30, 95% CI 0.66 to 2.56; low certainty evidence). The analyses provide evidence supporting an association between MMR/MMR+V/MMRV vaccines (Jeryl Lynn strain) and febrile seizures. Febrile seizures normally occur in 2% to 4% of healthy children at least once before the age of 5. The attributable risk febrile seizures vaccine-induced is estimated to be from 1 per 1700 to 1 per 1150 administered doses. The analyses provide evidence supporting an association between MMR vaccination and idiopathic thrombocytopaenic purpura (ITP). However, the risk of ITP after vaccination is smaller than after natural infection with these viruses. Natural infection of ITP occur in 5 cases per 100,000 (1 case per 20,000) per year. The attributable risk is estimated about 1 case of ITP per 40,000 administered MMR doses. There is no evidence of an association between MMR immunisation and encephalitis or encephalopathy (rate ratio 0.90, 95% CI 0.50 to 1.61; 2 observational studies; 1,071,088 children; low certainty evidence), and autistic spectrum disorders (rate ratio 0.93, 95% CI 0.85 to 1.01; 2 observational studies; 1,194,764 children; moderate certainty). There is insufficient evidence to determine the association between MMR immunisation and inflammatory bowel disease (odds ratio 1.42, 95% CI 0.93 to 2.16; 3 observational studies; 409 cases and 1416 controls; moderate certainty evidence). Additionally, there is no evidence supporting an association between MMR immunisation and cognitive delay, type 1 diabetes, asthma, dermatitis/eczema, hay fever, leukaemia, multiple sclerosis, gait disturbance, and bacterial or viral infections.

AUTHORS' CONCLUSIONS

Existing evidence on the safety and effectiveness of MMR/MMRV vaccines support their use for mass immunisation. Campaigns aimed at global eradication should assess epidemiological and socioeconomic situations of the countries as well as the capacity to achieve high vaccination coverage. More evidence is needed to assess whether the protective effect of MMR/MMRV could wane with time since immunisation.

Current Status of Mumps Virus Infection: Epidemiology, Pathogenesis, and Vaccine

Mumps is an important childhood infectious disease caused by mumps virus (MuV). We reviewed the epidemiology, pathogenesis, and vaccine development of mumps. Previous studies were identified using the key words “mumps” and “epidemiology”, “pathogenesis” or “vaccine” in MEDLINE, PubMed, Embase, Web of Science, and Google Scholar. We excluded the articles that were not published in the English language, manuscripts without abstracts, and opinion articles from the review. The number of cases caused by MuV decreased steeply after the introduction of the mumps vaccine worldwide. In recent years, a global resurgence of mumps cases in developed countries and cases of aseptic meningitis caused by some mumps vaccine strains have renewed the importance of MuV infection worldwide. The performance of mumps vaccination has become an important issue for controlling mumps infections. Vaccine development and routine vaccination are still effective measures to globally reduce the incidence of mumps infections. During outbreaks, a third of MMR vaccine is recommended for groups of persons determined by public authorities.

Mumps: an Update on Outbreaks, Vaccine Efficacy, and Genomic Diversity

Mumps is an acute viral infection characterized by inflammation of the parotid and other salivary glands. Persons with mumps are infectious from 2 days before through 5 days after parotitis onset, and transmission is through respiratory droplets. Despite the success of mumps vaccination programs in the United States and parts of Europe, a recent increase in outbreaks of mumps virus infections among fully vaccinated populations has been reported. Although the effectiveness of the mumps virus component of the measles-mumps-rubella (MMR) vaccine is suboptimal, a range of contributing factors has led to these outbreaks occurring in high-vaccination-coverage settings, including the intensity of exposure, the possibility of vaccine strain mismatch, delayed implementation of control measures due to the timeliness of reporting, a lack of use of appropriate laboratory tests (such as reverse transcription-PCR), and time since last vaccination. The resurgence of mumps virus infections among previously vaccinated individuals over the past decade has prompted discussions about new strategies to mitigate the risk of future outbreaks. The decision to implement a third dose of the MMR vaccine in response to an outbreak should be considered in discussions with local public health agencies. Traditional public health measures, including the isolation of infectious persons, timely contact tracing, and effective communication and awareness education for the public and medical community, should remain key interventions for outbreak control. Maintaining high mumps vaccination coverage remains key to U.S. and global efforts to reduce disease incidence and rates of complications.

Mumps in the Vaccination Age: Global Epidemiology and the Situation in Germany

Vaccination against mumps virus (MuV) (mostly measles-mumps-rubella) is routinely performed in more than 120 countries and has resulted in a distinct decrease of mumps incidence. However, alteration of mumps epidemiology has been observed in several countries after implementation of the vaccine but is sparsely documented. Moreover, outbreaks have occurred after starting vaccination, even in highly vaccinated populations. In the former German Democratic Republic (DDR) mumps was a notifiable disease but vaccination against mumps was not implemented. In the five eastern German states forming the DDR until 1990, mumps was not notifiable until 2001. Except for the lack of reporting between 1990–2000, data from Eastern Germany allow analysis of mumps epidemiology after initiating the vaccination campaign. For the period from 2001 to 2016 the data show that the incidence of mumps dropped notably after initiating vaccines, and was accompanied by an increase of the median age of patients with mumps. In Eastern Germany, no outbreaks were noted, while several outbreaks occurred in Western Germany, possibly due to a lower vaccination rate. Further literature analysis revealed that outbreaks were facilitated by waning immunity and crowding. Nevertheless, although vaccination prevented infection, the course of illness, once infected, was sometimes more complicated. In comparison to non-vaccinated populations, high rates of complicated courses occurred and were marked by orchitis, due to higher age of mumps patients. Therefore, refusing vaccination against mumps increases the risk of severe courses when living in a vaccinated population.

Vaccine waning and mumps re-emergence in the United States

After decades of declining mumps incidence amid widespread vaccination, the United States and other developed countries have experienced a resurgence in mumps cases over the last decade. Outbreaks affecting vaccinated individuals and communities with high vaccine coverage have prompted concerns about the effectiveness of the live attenuated vaccine currently in use. It is unclear whether immune protection wanes or whether the vaccine protects inadequately against currently circulating mumps virus lineages. Synthesizing data from six studies of mumps vaccine effectiveness, we estimated that vaccine-derived immune protection against mumps wanes on average 27 years (95% confidence interval, 16 to 51 years) after vaccination. After accounting for this waning, we found no evidence that the emergence of heterologous virus genotypes contributed to changes in vaccine effectiveness over time. A mathematical model of mumps transmission confirmed the central role of waning immunity to the vaccine in the re-emergence of mumps cases. Outbreaks from 2006 to the present among young adults, and outbreaks in the late 1980s and early 1990s among adolescents, aligned with peaks in mumps susceptibility of these age groups predicted to be due to loss of vaccine-derived protection. In contrast, evolution of mumps virus strains escaping immune pressure would be expected to cause a higher proportion of cases among children, not adolescents and young adults as observed. Routine use of a third vaccine dose at 18 years of age, or booster dosing throughout adulthood, may be a strategy to prevent mumps re-emergence and should be assessed in clinical trials.

Cellular and humoral immunity after vaccination or natural mumps infection

BACKGROUND

This study measured cell-mediated immunity (CMI) and serum antibody to clarify the basis of breakthrough after vaccination and reinfection after mumps.

METHODS

From a pool of 54 college students, 17 seronegative subjects and 14 subjects with intermediate level of antibodies against mumps were vaccinated with a monovalent mumps vaccine, and CMI was assessed using interferon-γ release assay.

RESULTS

CMI positivity according to pre-existing antibody level, defined as titer <2.0 index units, negative; 2.0-3.9 index units, intermediate; and ≥4.0 index units, positive, was 8/17 (47.1%), 9/14 (64.3%) and 19/23 (82.6%) before vaccination, respectively. Of the 17 seronegative subjects, seven (41.2%) had a history of vaccination and/or natural infection, four (57.1%) of whom were CMI positive or intermediate. Ten (71%) of 14 subjects with intermediate antibody level had a history of vaccination or natural infection, eight (80%) of whom were CMI positive or intermediate. After vaccination the interferon (IFN)-γ and antibody titers increased significantly, but seven (41.2%) of the 17 seronegative subjects and 13 (92.9%) of the 14 intermediate-level subjects tested positive for both antibody and CMI. In a comparison of the natural infection group (confirmed as IgG seropositive and/or CMI positive without vaccination) versus the vaccination group, IgG antibody titer (mean ± SD) was 14.4 ± 8.0 versus 3.6 ± 2.4 index units (P < 0.01) and IFN-γ was 122.7 ± 90.0 pg/mL versus 59.5 ± 37.8 pg/mL (P > 0.05), respectively.

CONCLUSION

Vaccination or even natural mumps infection did not always induce both cellular and humoral immunity.

Virus genotypes and responses of serum-specific antibodies in children with primary mumps and mumps reinfection

BACKGROUND

Research on children with mumps reinfection after natural infection is limited; there are currently no studies on virus-specific antibody responses in paired sera or genotyping of isolated viruses.

METHODS

This study included 281 children (147 boys and 134 girls, age: 1.2-15.9 y) with primary mumps (240), mumps reinfection after natural infection (9), mumps after previous vaccination (26), and vaccine-associated mumps (6). We measured mumps-specific serum antibodies and analyzed isolated virus genes.

RESULTS

During acute illness, series-specific IgM and IgG titers exceeded cutoff values in 240 and 232 children with primary mumps, respectively. During convalescence, IgM antibodies were positive in seven and negative in two of nine children with mumps reinfection occurring after natural infection; among 26 previously vaccinated children, 13 were positive and 13 negative. Mumps viruses were isolated from viral cultures from 42 of the 51 children. Except for 6 vaccine-associated cases, all remaining 36 cases of isolated mumps virus were identified as genotype G.

CONCLUSION

These results suggest that measurement of IgM antibody on any day of acute illness may be indicative of primary mumps but may be inconsistent for diagnosing mumps reinfection after natural infection or previous vaccination.

A Mumps Outbreak in Vojvodina, Serbia, in 2012 Underlines the Need for Additional Vaccination Opportunities for Young Adults

In 2012, mumps was introduced from Bosnia and Herzegovina to Vojvodina, causing an outbreak with 335 reported cases. The present manuscript analyses the epidemiological and laboratory characteristics of this outbreak, identifies its main causes and suggests potential future preventive measures. Sera of 133 patients were tested for mumps-specific antibodies by ELISA and 15 nose/throat swabs were investigated for mumps virus RNA by RT-PCR. IgG antibodies were found in 127 patients (95.5%). Mumps infection was laboratory-confirmed in 53 patients, including 44 IgM and 9 PCR positive cases. All other 282 cases were classified as epidemiologically-confirmed. More than half of the patients (n = 181, 54%) were 20–29 years old, followed by the 15–19 age bracket (n = 95, 28.4%). Twice as many males as females were affected (67% versus 33%). Disease complications were reported in 13 cases (3.9%), including 9 patients with orchitis and 4 with pancreatitis. According to medical records or anamnestic data, 190 patients (56.7%) were immunized with two doses and 35 (10.4%) with one dose of mumps-containing vaccine. The Serbian sequences corresponded to a minor genotype G variant detected during the 2011/2012 mumps outbreak in Bosnia and Herzegovina. Vaccine failures, the initial one-dose immunization policy and a vaccine shortage between 1999 and 2002 contributed to the outbreak. Additional vaccination opportunities should be offered to young adults during transition periods in their life trajectories.

Epidemiologic features of mumps in Taiwan from 2006 to 2011: a new challenge for public health policy

BACKGROUND

The adoption of a second dose of the measles-mumps-rubella (MMR) vaccine among Taiwanese school children began in 2001. However, during that time, mumps cases continued to occur. The purpose of the present study was to assess the epidemiology and vaccination policy for mumps in Taiwan.

METHODS

We examined the data on mumps cases collected by the Taiwan Centers for Disease Control (Taiwan CDC) between 2006 and 2011.

RESULTS

During the 6-year study period, a total of 6612 cases of mumps were reported to the Taiwan CDC. Of the patients with known vaccination status, 62% received one dose of the MMR vaccine or no vaccine. The incidence of mumps ranged from 4.18 to 5.28 per 100 000 population and peaked in 2007. Males had a higher incidence of mumps than females (5.9 vs. 3.7 per 100 000 population; P=0.024). Children between 5 and 6 years of age had the highest incidence of mumps, and those 20 years and older had the lowest incidence. Compared to those who received two doses of the MMR vaccine, patients who were not vaccinated or received a single dose of the vaccine had a higher risk of suffering from complications and/or hospitalization.

CONCLUSIONS

In Taiwan, more than 60% of mumps cases received either no dose or one dose of the MMR vaccine. Monitoring mumps through biological testing and instituting a second dose of the MMR vaccine for children is needed for the elimination of mumps in Taiwan.

Mumps outbreak and laboratory diagnosis

BACKGROUND

Several mumps outbreaks have been reported in Europe and in the United States among highly vaccinated populations. Biological diagnosis is classically based on the detection of mumps-specific IgM, but the ability of serological tests to confirm mumps infection seems to be limited among vaccinated patients.

OBJECTIVES

We aim to report a mumps outbreak in an engineering school in Grenoble, France, from February to June 2013 and results of the biological testing.

STUDY DESIGN

WHO definitions were used to define cases. Mumps--specific IgM and IgG were assessed by a commercially available EIA. Mumps RNA detection by real time reverse transcriptase polymerase chain reaction tests (RT-PCR) and mumps genotyping were performed by the French National Reference Centre for Paramyxoviridae.

RESULTS

Sixty two mumps patient-cases were identified using WHO case definitions, 20 being biologically explored, of which 17 were confirmed by biological tests. Vaccination status was documented for 27 patients/62: 4 (14.8%) patients had received one dose of MMR vaccine, and 23 (85.2) two doses of MMR vaccine. Among the biologically explored patients, 83% had a positive RT PCR at the first sampling whereas only 45% had positive or equivocal IgM. All the genotyped strains were genotype G.

CONCLUSIONS

Mumps laboratory diagnosis in a highly vaccinated population is challenging. Serological tests among vaccinated patients should be interpreted cautiously and confirmed by RT-PCR tests at the beginning of a mumps outbreak.

Smoking and older age associated with mumps in an outbreak in a group of highly-vaccinated individuals attending a youth club party, the Netherlands, 2012

We describe a mumps outbreak in a highly-vaccinated population attending a party at a youth club. In a retrospective cohort study with 60 of approximately 100 participants responding, vaccination status was verified for 58/59 respondents, of whom 54 were vaccinated twice and four once. The attack rate was 22% (13 cases, all vaccinated), with smoking at the party (risk ratio (RR) 3.1; 95% confidence interval (CI): 1.6–6.0, p=0.001) and age ≥21 years (RR 4.7; 95% CI: 2.1–10.2, p<0.0001) as risk factors for disease in the binominal regression analysis. Mild upper respiratory illness was also highly prevalent in those who did not meet the mumps case definition (n=46) after the party, suggesting that mumps virus infection may cause mild disease in vaccinated individuals. Our investigation adds toevidence that crowded social events and smoking may facilitate spread of mumps virus among vaccinated populations, with waning immunity playing a role. The suggestion that mumps virus infection in vaccinated individuals may manifest as mild upper respiratory illness could have implications for transmission and warrants further investigation.

Assessing mumps outbreak risk in highly vaccinated populations using spatial seroprevalence data

Mumps is a potentially severe viral infection. The incidence of mumps has declined dramatically in high-income countries since the introduction of mumps antigen-containing vaccines. However, recent large outbreaks of mumps in highly vaccinated populations suggest waning of vaccine-induced immunity and primary vaccine failure. In this paper we present a simple method for identifying geographic regions with high outbreak potential, demonstrated using 2006 mumps seroprevalence data from Belgium and Belgian vaccination coverage data. Predictions of the outbreak potential in terms of the effective reproduction number in future years signal an increased risk of new mumps outbreaks. Literature reviews on serological information for both primary vaccine failure and waning immunity provide essential information for our predictions. Tailor-made additional vaccination campaigns would be valuable for decreasing local pockets of susceptibility, thereby reducing the risk of future large-scale mumps outbreaks.

Epidemiology and the economic assessment of a mumps outbreak in a highly vaccinated population, Orange County, New York, 2009-2010

Studies assessing the economic burden of a mumps outbreak in a highly vaccinated population are limited. The Orange County Health Department (OCHD), New York State Department of Health (NYS DOH), and the Centers for Disease Control and Prevention conducted a mumps investigation in an affected village with a highly vaccinated population. To understand the epidemiology, standardized mumps case definition and active surveillance were used to identify mumps cases. In addition, an economic assessment of a combined outbreak investigation and third dose measles-mumps-rubella (MMR) vaccine intervention conducted by OCHD and NYS DOH was performed; estimated by retrospectively evaluating public health response-related activities including use of a third dose of MMR vaccine. From September 24, 2009, through June 15, 2010, 790 mumps cases were reported-64% were male and highest attack rate was among 11-17 year age group (99.1 cases per 1000 individuals). Of the 658 cases with known vaccination history, 83.6% had documentation of 2 doses of mumps containing vaccine. No deaths were reported. The 2 major exposure settings were schools (71.8%) and households (22.5%). Approximately 7736 h of public health personnel time were expended with the total approximate cost of US $463,000, including US $34,392 for MMR vaccine-the estimated cost per household was US $827. Mumps continues to be endemic in many parts of the world, resulting in importations into the United States. Large mumps outbreaks similar to this in highly vaccinated populations may require considerable investigation and control activities.

Mumps vaccine effectiveness and risk factors for disease in households during an outbreak in New York City

BACKGROUND AND OBJECTIVES

Mumps outbreaks have been reported among vaccinated populations, and declining mumps vaccine effectiveness (VE) has been suggested as one possible cause. During a large mumps outbreak in New York City, we assessed: (1) VE of measles-mumps-rubella vaccine (MMR) against mumps and (2) risk factors for acquiring mumps in households.

METHODS

Cases of mumps were investigated using standard methods. Additional information on disease and vaccination status of household contacts was collected. Case households completed follow-up phone interviews 78-198 days after initial investigation to ascertain additional cases. Mumps cases meeting the study case definition were included in the analysis. Risk factors for mumps were assessed, and VE was calculated using secondary household attack rates.

RESULTS

Three hundred and eleven households with 2176 residents were included in the analysis. The median age of residents was 13 years (range <1-85), and 462 (21.2%) residents met the study mumps case definition. Among 7-17 year olds, 89.7% received one or more doses of MMR vaccine, with 76.7% receiving two doses. Young adults aged 10-14 years (OR=2.4, CI=1.3-4.7) and 15-19 years (OR=2.5, CI=1.3-5.0) were at highest risk of mumps. The overall 2-dose VE for secondary contacts aged five and older was 86.3% (CI 63.3-94.9).

CONCLUSIONS

The two-dose effectiveness of MMR vaccine against mumps was 86.3%, consistent with other published mumps VE estimates. Many factors likely contributed to this outbreak. Suboptimal MMR coverage in the affected population combined with VE may not have conferred adequate immunity to prevent transmission and may have contributed to this outbreak. Achieving high MMR coverage remains the best available strategy for prevention of mumps outbreaks.

Comparison of the sensitivity of laboratory diagnostic methods from a well-characterized outbreak of mumps in New York city in 2009

A mumps outbreak in upstate New York in 2009 at a summer camp for Orthodox Jewish boys spread into Orthodox Jewish communities in the Northeast, including New York City. The availability of epidemiologic information, including vaccination records and parotitis onset dates, allowed an enhanced analysis of laboratory methods for mumps testing. Serum and buccal swab samples were collected from 296 confirmed cases with onsets from September through December 2009. All samples were tested using the Centers for Disease Control and Prevention (CDC) capture IgM enzyme immunoassay (EIA) and a real-time reverse transcription-PCR (rRT-PCR) that targets the short hydrophobic gene. A subset of the samples (n = 205) was used to evaluate 3 commercial mumps IgM assays and to assess the sensitivity of using an alternative target gene (nucleoprotein) in the rRT-PCR protocol. Among 115 cases of mumps with 2 documented doses of measles, mumps, and rubella (MMR) vaccine, the CDC capture IgM EIA detected IgM in 51% of serum samples compared to 9% to 24% using three commercial IgM assays. The rRT-PCR that targeted the nucleoprotein gene increased RNA detection by 14% compared to that obtained with the original protocol. The ability to detect IgM improved when serum was collected 3 days or more after symptom onset, whereas sensitivity of RNA detection by rRT-PCR declined when buccal swabs were collected later than 2 days after onset. Selection of testing methods and timing of sample collection are important factors in the ability to confirm infection among vaccinated persons. These results reinforce the need to use virus detection assays in addition to serologic tests.

Seroprevalence of measles-, mumps- and rubella-specific IgG antibodies in German children and adolescents and predictors for seronegativity

We have undertaken a seroprevalence study with more than 13,000 children, who had been included in the German KIGGS survey, a representative sample of children and adolescents 0-17 years of age. The IgG titres against measles, mumps and rubella were determined in 1 to 17 year olds While 88.8% of the children were MMR-vaccinated at least once, 76.8% of children aged 1 to 17 years showed prevalence of antibodies to MMR. The highest seronegativity was seen with respect to mumps. Gender differences were most pronounced with regard to rubella IgG titres: girls aged 14 to 17 years were best protected, although seronegativity in 6.8% of this vulnerable group still shows the need of improvement. Search for predictors of missing seroprevalence identified young age to be the most important predictor. Children living in the former West and children born outside of Germany had a higher risk of lacking protection against measles and rubella, while children with a migration background but born in Germany were less often seronegative to measles antibodies than their German contemporaries. An association of seronegativity and early vaccination was seen for measles but not for mumps and rubella. A high maternal educational level was associated with seronegativity to measles and rubella. In vaccinated children, seronegativity was highest for mumps and lowest for rubella. For mumps, high differences were observed for seronegativity after one-dose and two-dose vaccination, respectively. Seronegativity increases as time since last vaccination passes thus indicating significant waning effects for all three components of MMR.

No evidence of mumps transmission during air travel, United States, November 1, 2006-October 31, 2010

Since November 2006, flight-related mumps contact investigations were conducted in the United States only for flights ≥5 h long after an investigation showed minimal risk of mumps transmission on flights <5 h. Because the transmission risk on longer flights had not been evaluated, we investigated whether there was evidence to support the guidelines. We examined data from mumps contact investigations that were initiated by the US Centers for Disease Control and Prevention (CDC) from November 2006 to October 2010. We also cross-referenced passenger-contact data with data on mumps cases in the National Notifiable Diseases Surveillance System (NNDSS). Twenty-seven cases met inclusion criteria. Of 246 passengers identified as contacts, 166 (67%) were distributed to a US health department for contact tracing. Outcomes were reported for 21 (13%) of those 166 passengers. No secondary cases of mumps among passenger contacts were reported or identified by cross-referencing NNDSS data. The findings suggested that in-flight risk of mumps transmission is not high. Furthermore, these investigations have low yield, are resource intensive, there is no post-exposure prophylaxis, and mumps transmission has not been eliminated in the United States. Therefore, CDC discontinued conducting flight-related mumps contact investigations in May 2011.

Seroepidemiology of mumps in Europe (1996-2008): why do outbreaks occur in highly vaccinated populations?

Mumps outbreaks have recently been recorded in a number of highly vaccinated populations. We related seroprevalence, epidemiological and vaccination data from 18 European countries participating in The European Sero-Epidemiology Network (ESEN) to their risk of mumps outbreaks in order to inform vaccination strategies. Samples from national population serum banks were collected, tested for mumps IgG antibodies and standardized for international comparisons. A comparative analysis between countries was undertaken using age-specific mumps seroprevalence data and information on reported mumps incidence, vaccine strains, vaccination programmes and vaccine coverage 5-12 years after sera collection. Mean geometric mumps antibody titres were lower in mumps outbreak countries [odds ratio (OR) 0·09, 95% confidence interval (CI) 0·01-0·71)]. MMR1 vaccine coverage ⩾95% remained protective in a multivariable model (P < 0·001), as did an interval of 4-8 years between doses (OR 0·08, 95% CI 0·01-0·85). Preventing outbreaks and controlling mumps probably requires several elements, including high-coverage vaccination programmes with MMR vaccine with 4-8 years between doses.

Vaccines for measles, mumps and rubella in children

BACKGROUND

Mumps, measles and rubella (MMR) are serious diseases that can lead to potentially fatal illness, disability and death. However, public debate over the safety of the trivalent MMR vaccine and the resultant drop in vaccination coverage in several countries persists, despite its almost universal use and accepted effectiveness.

OBJECTIVES

To assess the effectiveness and adverse effects associated with the MMR vaccine in children up to 15 years of age.

SEARCH METHODS

For this update we searched the Cochrane Central Register of Controlled Trials (CENTRAL) (The Cochrane Library 2011, Issue 2), which includes the Cochrane Acute Respiratory Infections Group's Specialised Register, PubMed (July 2004 to May week 2, 2011) and Embase.com (July 2004 to May 2011).

SELECTION CRITERIA

We used comparative prospective or retrospective trials assessing the effects of the MMR vaccine compared to placebo, do nothing or a combination of measles, mumps and rubella antigens on healthy individuals up to 15 years of age.

DATA COLLECTION AND ANALYSIS

Two review authors independently extracted data and assessed methodological quality of the included studies. One review author arbitrated in case of disagreement.

MAIN RESULTS

We included five randomised controlled trials (RCTs), one controlled clinical trial (CCT), 27 cohort studies, 17 case-control studies, five time-series trials, one case cross-over trial, two ecological studies, six self controlled case series studies involving in all about 14,700,000 children and assessing effectiveness and safety of MMR vaccine. Based on the available evidence, one MMR vaccine dose is at least 95% effective in preventing clinical measles and 92% effective in preventing secondary cases among household contacts.Effectiveness of at least one dose of MMR in preventing clinical mumps in children is estimated to be between 69% and 81% for the vaccine prepared with Jeryl Lynn mumps strain and between 70% and 75% for the vaccine containing the Urabe strain. Vaccination with MMR containing the Urabe strain has demonstrated to be 73% effective in preventing secondary mumps cases. Effectiveness of Jeryl Lynn containing MMR in preventing laboratory-confirmed mumps cases in children and adolescents was estimated to be between 64% to 66% for one dose and 83% to 88% for two vaccine doses. We did not identify any studies assessing the effectiveness of MMR in preventing rubella.The highest risk of association with aseptic meningitis was observed within the third week after immunisation with Urabe-containing MMR (risk ratio (RR) 14.28; 95% confidence interval (CI) from 7.93 to 25.71) and within the third (RR 22.5; 95% CI 11.8 to 42.9) or fifth (RR 15.6; 95% CI 10.3 to 24.2) weeks after immunisation with the vaccine prepared with the Leningrad-Zagreb strain. A significant risk of association with febrile seizures and MMR exposure during the two previous weeks (RR 1.10; 95% CI 1.05 to 1.15) was assessed in one large person-time cohort study involving 537,171 children aged between three months and five year of age. Increased risk of febrile seizure has also been observed in children aged between 12 to 23 months (relative incidence (RI) 4.09; 95% CI 3.1 to 5.33) and children aged 12 to 35 months (RI 5.68; 95% CI 2.31 to 13.97) within six to 11 days after exposure to MMR vaccine. An increased risk of thrombocytopenic purpura within six weeks after MMR immunisation in children aged 12 to 23 months was assessed in one case-control study (RR 6.3; 95% CI 1.3 to 30.1) and in one small self controlled case series (incidence rate ratio (IRR) 5.38; 95% CI 2.72 to 10.62). Increased risk of thrombocytopenic purpura within six weeks after MMR exposure was also assessed in one other case-control study involving 2311 children and adolescents between one month and 18 years (odds ratio (OR) 2.4; 95% CI 1.2 to 4.7). Exposure to the MMR vaccine was unlikely to be associated with autism, asthma, leukaemia, hay fever, type 1 diabetes, gait disturbance, Crohn's disease, demyelinating diseases, bacterial or viral infections.

AUTHORS' CONCLUSIONS

The design and reporting of safety outcomes in MMR vaccine studies, both pre- and post-marketing, are largely inadequate. The evidence of adverse events following immunisation with the MMR vaccine cannot be separated from its role in preventing the target diseases.

Mumps outbreak in Israel's highly vaccinated society: are two doses enough?

Mumps outbreaks in recent years have given rise to questions about the effectiveness of the mumps vaccine. This study examined the epidemiological data from a recent mumps outbreak in Israel and from outbreaks in other countries with high vaccination coverage, and considered whether long-established vaccination policies designed to protect against mumps are in need of revision. Of over 5000 case patients in the Israeli outbreak, half of whom were in the Jerusalem health district, nearly 40% were aged ≥15 years and, of those whose vaccination status was known, 78% had been fully vaccinated for their age - features similar to those in recent mumps outbreaks in Europe and North America. The epidemiological and laboratory evidence suggests that many previously vaccinated adolescents and young adults are now susceptible to mumps because their vaccine-based immunity has waned. Booster vaccination programmes for those at high risk of infection during mumps outbreaks - particularly those in congregate living environments - merit priority consideration.

Assessment of mumps virus-specific antibodies by different serological assays: which test correlates best with mumps immunity?

Mumps is one of the vaccine-preventable childhood diseases and it has not yet been eradicated in Germany. This raises the question as to whether the available mumps vaccines are effective enough to prevent mumps and which antibody test system allows the authentic assigning of mumps-specific immunity. In an attempt to answer this question, we analysed 227 sera samples from medical students of the University Hospital Frankfurt/Main, Germany, using different test systems: indirect immune fluorescence, neutralisation assay, routine ELISA and newly developed immunoassays, which contain the mumps nucleoprotein and the wild-type strain Enders ATCC VR106, respectively. Mumps vaccination coverage of the screened collective amounted to 75.1%, which differs notably from the detected mumps-specific seropositivity rates in the literature (range 53.3% to 82.4%). In contrast, a small group of unvaccinated students had much higher seropositivity rates. Of course, assigned vaccination coverage and calculated seropositivity rates are not effective enough to interrupt the transmission of the mumps virus. The often-occurring mumps outbreaks, some in highly vaccinated populations, may not always demonstrate vaccine failure. The investigation of newly developed test systems and the occurrence of different mumps virus genotypes should also be considered.

Mumps outbreak in the Republic of Moldova, 2007-2008

BACKGROUND

Moldova experienced a nationwide mumps outbreak between 2007 and 2008. Single-dose monovalent mumps vaccination at 15 to 18 months was introduced in 1983, replaced by a 2-dose MMR schedule at age 1 and 6 to 7 years in 2002. We investigated the outbreak to quantify its extent, explore the role of primary and secondary vaccine failure, and provide control recommendations.

METHODS

We analyzed national mumps surveillance and vaccination coverage data to estimate vaccine effectiveness (VE) using the screening method. A retrospective cohort study in 5 educational institutions was conducted to determine age-specific attack rates (ARs) and VE. We compared vaccine strain-specific ARs. Isolation and genotyping of mumps virus strains were performed.

RESULTS

Of 31,142 cases reported during October 2007 and July 2008, 80% were in 15- to 24-year-olds. Of cases with information (66%), 92% were vaccinated once, 4% twice. One-dose mumps VE estimates based on surveillance data over 1997-2001 declined from 91% (95% CI: 88%-92%) in 2-year-olds to 72% (70%-74%) in 15- to 19-year-olds. In the cohort study (n = 1589), VE was -40% (-120% to 20%) for 1 dose. For 2 doses it was 62% (-43% to 90%) in 13- to 15-year-olds. ARs were higher in individuals vaccinated with Urabe strains (43%) than with Leningrad-Zagreb strains (14%, P < 0.001). Mumps virus genotype G5 was identified.

CONCLUSIONS

Low effectiveness of single-dose mumps vaccination was the main cause of the outbreak. Waning immunity may have contributed to this. The risk of mumps in 2-dose vaccinees was low. Other countries in which large population groups have received <2 doses of mumps vaccine may face similar outbreaks.

Are we hitting immunity targets? The 2006 age-specific seroprevalence of measles, mumps, rubella, diphtheria and tetanus in Belgium

Susceptibility to vaccine-preventable diseases in Belgium in 2006 was estimated from a serum survey. Immunoglobulins against measles, mumps, rubella (MMR) and diphtheria at all available ages (1-65 years), and against tetanus in >40-year-olds, were measured by ELISA. Age-standardized overall seronegativity for MMR was low (3·9%, 8·0%, 10·4%, respectively). However, the World Health Organization's targets for measles elimination were not met in 5- to 24-year-olds and about 1 in 7 women at childbearing age (15-39 years) were seronegative for rubella. In adults >40 years, tetanus immunity (87·2%, >0·16 IU/ml) largely exceeded diphtheria immunity (20-45%, >0·1 IU/ml). Despite free universal vaccination against MMR for more than 20 years and against diphtheria and tetanus for almost 60 years, our study revealed specific age groups remaining at risk for infection with these pathogens.

Circulation of mumps virus genotypes in Spain from 1996 to 2007

Although the WHO recommends the use of genotyping as a tool for epidemiological surveillance for mumps, limited data on mumps virus (MV) genotype circulation that may be used to trace the patterns of virus spread are available. We describe the first complete series of data from Spain. The small hydrophobic region was sequenced from 237 MV-positive samples from several regions of Spain collected between 1996 and 2007. Six different genotypes were identified: A, C, D (D1), G (G1, G2), H (H1, H2), and J. Genotype H1 was predominant during the epidemic that occurred from 1999 to 2003 but was replaced by genotype G1 as the dominant genotype in the epidemic that occurred from 2005 to 2007. The same genotype G1 strain caused concomitant outbreaks in different parts of the world (the United States, Canada, and the United Kingdom). The remaining genotypes (genotypes A, C, D, and J) appeared in sporadic cases or small limited outbreaks. This pattern of circulation seems to reflect continuous viral circulation at the national level, despite the high rates of vaccine coverage.

Mumps resurgences in the United States: A historical perspective on unexpected elements

In 2006 the United States experienced the largest nationwide mumps epidemic in 20 years, primarily affecting college dormitory residents. Unexpected elements of the outbreak included very abrupt time course (75% of cases occurred within 90 days), geographic focality (85% of cases occurred in eight rural Midwestern states), rapid upward and downward shift in peak age-specific attack rate (5-9-year olds to 18-24-year olds, then back), and two-dose vaccine failure (63% of case-patients had received two doses). To construct a historical context in which to understand the recent outbreak, we reviewed US mumps surveillance data, vaccination coverage estimates, and relevant peer-reviewed literature for the period 1917-2008. Many of the unexpected features of the 2006 mumps outbreak had been reported several times previously in the US, e.g., the 1986-1987 mumps resurgence had extremely abrupt onset, rural geographic focality, and an upward-then-downward age shift. Evidence suggested recurrent mumps outbreak patterns were attributable to accumulation of susceptibles in dispersed situations where the risk of endemic disease exposure was low and were triggered when this susceptible population was brought together in crowded living conditions. The 2006 epidemic followed this pattern, with two unique variations: it was preceded by a period of very high vaccination rates and very low disease incidence and was characterized by two-dose failure rates among adults vaccinated in childhood. Data from the past 80 years suggest that preventing future mumps epidemics will depend on innovative measures to detect and eliminate build-up of susceptibles among highly vaccinated populations.

Investigation of a mumps outbreak among university students with two measles-mumps-rubella (MMR) vaccinations, Virginia, September-December 2006

Following the clinical diagnosis of the first case of mumps on September 22, 2006 at the University of Virginia (UVA), 52 suspected cases were identified through active surveillance for mumps by the end of December 2006. Samples were collected from 47 students who presented with parotitis despite a documented history of two doses of measles, mumps, and rubella (MMR) vaccine. Six of 47 serum samples (13%) were positive for mumps IgM, and 46/47 specimens were positive for mumps IgG. Endpoint titration of acute phase serum samples from laboratory-confirmed cases did not provide evidence that elevated serum IgG is a consistent marker for infection among cases due to secondary vaccine failure. Buccal swab samples from 39 of the 47 students were tested by real-time reverse transcription-polymerase chain reaction (RT-PCR) and/or viral culture. Mumps virus or mumps RNA was detected in 12 of 39 buccal samples (31%). Genetic analysis of the virus from the outbreak at UVA indicated that the outbreak was not linked to the large mumps outbreak in the Midwestern US that occurred earlier in 2006. Our findings support the use of viral detection to improve laboratory diagnosis of mumps among persons who have received two doses of MMR.

Risk factors for mumps at a university with a large mumps outbreak

OBJECTIVES

Routine measles-mumps-rubella (MMR) vaccine use has greatly decreased the incidence of mumps in the U.S. However, a resurgence of mumps occurred in 2006. We investigated the large outbreak at a university and assessed risk factors for disease.

METHODS

We described the outbreak and conducted a case-control study. We interviewed case students (identified from student health service and health department records) and control students (selected from a randomly ordered administrative list) and assessed their vaccination status. We compared case students with > or = 2 MMR doses and control students with > or = 2 MMR doses in univariate and multivariate analyses.

RESULTS

The mean age of the 174 case students was 20.9 years; 65% were women. Ninety-seven case students and 147 control students were enrolled in the study. Two-dose MMR coverage was 99% among case and control students with complete records. Only 33% of case students reported exposure to someone with mumps. Case students were more likely than control students to be aged 18 to 19 years (vs. aged 22 years, adjusted odds ratio [AOR] = 5.55; 95% confidence interval [CI] 2.09, 14.74), to report exposure to mumps (AOR=2.31, 95% CI 1.13, 4.73), and to have worked/volunteered on campus (AOR=2.91, 95% CI 1.33, 6.33). Also, women in dormitories had increased odds of mumps compared with men in dormitories.

CONCLUSION

High two-dose MMR coverage was not sufficient to prevent the outbreak. Further study is needed to better understand the effects of dormitory residency and gender on mumps transmission. Clinicians should be vigilant for mumps in young adults presenting with parotitis regardless of immunization history.

Effectiveness of Jeryl Lynn-containing vaccine in Spanish children

We evaluated the effectiveness of the Jeryl Lynn strain vaccine in a large outbreak of mumps in Navarre, Spain, 2006-2008. Each of the 241 cases of mumps occurring in children over 15 months of age born between 1998 and 2005 was compared with 5 controls individually matched by sex, birth date, district of residence and paediatrician. Vaccination history was obtained blindly from clinical records. Conditional logistic regression was used to obtain the matched odds ratios (ORs), and effectiveness was calculated as 1-OR. Some 70% of cases had received one dose of measles-mumps-rubella vaccine, and 24% had received two doses. Overall vaccine effectiveness was 72% (95% CI, 39-87%). Two doses were more effective (83%; 54-94%) than a single dose (66%; 25-85%). Among vaccinated children, risk was higher in those who had received the first dose after 36 months of age (OR=3.1; 1.2-8.4) and those who had received the second dose 3 or more years before study enrolment (OR=10.2; 1.5-70.7). Early waning of immunity in children after the second dose may contribute to reduced vaccine effectiveness for mumps prevention.

Characterization of large mumps outbreak among vaccinated Palestinian refugees

During a large mumps virus (MuV) outbreak which occurred in the Palestinian refugee camps of the West Bank, 68.1% (2,636/3,871) of the cases were vaccinated with one dose of trivalent measles, mumps, and rubella (MMR) vaccine. Attack rates by camp ranged from less than 1 case per 1,000 people in the population to 43/1,000 (overall, 11/1,000). The outbreak lasted from December 2003 to June 2005, with two peaks, one from April to May 2004 and the other from March to April 2005. To control the outbreak, a mass MMR vaccination campaign was conducted in May 2005. Evaluation of the immune status of cases (n=59) and healthy controls (n=51) revealed high levels of mumps immunoglobulin G (IgG) and a low MuV-specific IgM in clinical cases indicative of a booster immune response. This suggested a secondary rather than a primary infection due to the insufficient protection conferred by the single vaccine dose included in the vaccination program. This prediction was further confirmed by the low seroprevalence (68.6%) found in the healthy control group, which was below the threshold level required for MuV herd immunity. Mumps diagnosis was established mainly by reverse transcription-PCR in clinical samples obtained within 48 h from the onset of disease. Of the parotid fluids and nasopharyngeal aspirates analyzed, 92% were positive for MuV RNA, while only 33% of the urine samples were positive. Phylogenetic analysis of the MuV SH gene identified the outbreak strain as the H genotype, which has been in circulation worldwide at least since 1989.

Routine immunization of adults in Canada: Review of the epidemiology of vaccine-preventable diseases and current recommendations for primary prevention

Vaccination is one of the greatest achievements in public health of the 20th century. However, the success of vaccine uptake and adherence to immunization guidelines seen in pediatric populations has not been observed among adult Canadians. As a result of the disparity in susceptibility to vaccine-preventable disease, there has been an increasing shift of vaccine-preventable childhood diseases into adult populations. Accordingly, morbidity and mortality due to vaccine-preventable illnesses now occur disproportionately in adults. All Canadians, irrespective of age, should have immunity to measles, mumps, rubella, tetanus, diphtheria, pertussis and varicella. All adult Canadians with significant medical comorbidities or those older than 65 years of age should receive the pneumococcal polysaccharide vaccine and yearly trivalent inactivate influenza vaccines. The present review summarizes the burden of illness of these vaccine-preventable diseases in the Canadian adult population and reviews the current immunization recommendations. Vaccination of all Canadians to these common agents remains a vital tool to decrease individual morbidity and mortality and reduce the overall burden of preventable disease in Canada.

Mumps outbreaks in vaccinated populations: are available mumps vaccines effective enough to prevent outbreaks?

Increased reports of mumps in vaccinated populations prompted a review of the performance of mumps vaccines. The effectiveness of prior vaccination with 1 dose of vaccine ranged from 72.8% to 91% for the Jeryl Lynn strain, from 54.4% to 93% for the Urabe strain, and from 0% to 33% for the Rubini strain. Vaccine effectiveness after 2 doses of mumps vaccine was reported in 3 outbreaks and ranged from 91% to 94.6%. There was evidence of waning immunity, which is a likely factor in mumps outbreaks, aggravated by possible antigenic differences between the vaccine strain and outbreak strains. Inadequate vaccine coverage or use of the Rubini vaccine strain accounted for the majority of outbreaks reviewed; however, some outbreaks could not be prevented, despite high vaccination coverage with 2 doses of the Jeryl Lynn vaccine strain. Our findings indicate the need for more-effective mumps vaccines and/or for review of current vaccination policies to prevent future outbreaks.

Mumps epidemiology and immunity: the anatomy of a modern epidemic

The success of the measles, mumps, and rubella 2-dose vaccination program led public health officials in 1998 to set a goal to eliminate endemic transmission of mumps virus by 2010 in the United States. The large outbreak of mumps in the spring of 2006 has led public health officials to re-evaluate this goal and to recognize that the transmission and epidemiology of mumps in highly vaccinated populations may be different than anticipated. During 2006, a total of 6584 confirmed and probable cases of mumps were reported to the Centers for Disease Control and Prevention and most of these, 5865, occurred between January 1 and July 31. The peak of the outbreak was in April and seemed to be focused on college campuses in 9 midwestern states with Iowa having the highest attack rate. College campuses with mumps outbreaks included ones with 77% to 97% of students having had 2 doses of a mumps vaccine. Diagnosing mumps proved to be problematic in vaccinated persons (ie, laboratory tests seemed to be insensitive and some apparent mumps cases had mild nonclassic illness). The outbreak demonstrated that mumps can sometimes transmit efficiently in highly vaccinated populations and the clinical and laboratory diagnosis of mumps in vaccinated persons is more difficult than in naive persons. The reason for this mumps outbreak is not clear but probably results from multiple factors contributing to an overall increase in susceptibility and/or transmission.

Mumps vaccine performance among university students during a mumps outbreak

BACKGROUND

The largest reported mumps outbreak at a US college in 19 years occurred in 2006 at a Kansas university with a 2-dose measles-mumps-rubella (MMR) vaccination policy. We assessed vaccine performance and mumps risk factors, including the possibility of waning vaccine protection.

METHODS

Case students were compared with a cohort of the university's approximately 19,000 undergraduates. The secondary attack rate for clinical mumps was determined among roommates exposed to case students. Time from receipt of the second dose of MMR vaccine was compared between case students and roommates without mumps.

RESULTS

Coverage with > or =2 dose of MMR vaccine was > or =95% among 140 undergraduate case students and 444 cohort students. The secondary attack rate for clinical mumps among roommates who had received 2 doses of vaccine ranged from 2.2% to 7.7%, depending on the case definition. Compared with roommates without mumps, case students were more likely (odds ratio, 2.46; 95% confidence interval, 1.25-4.82) to have received their second dose of MMR vaccine > or =10 years earlier. The odds of being a case student increased with each 1-year increase in time from receipt of the second dose of MMR vaccine (odds ratio, 1.36; 95% confidence interval, 1.10-1.68) among case students and roommates aged 18-19 years but not among those aged > or =20 years. Students aged 18-19 years had a higher risk of mumps (risk ratio, 3.14; 95% confidence interval, 1.60-6.16), compared with students aged > or =22 years; women living in dormitories had increased risk of mumps (risk ratio, 1.95; 95% confidence interval, 1.01-3.76), compared with men not living in dormitories.

CONCLUSION

High 2-dose MMR coverage protected many students from developing mumps but was not sufficient to prevent the mumps outbreak. Vaccine-induced protection may wane. Similar US settings where large numbers of young adults from wild-type naive cohorts live closely together may be at particular risk for mumps outbreaks.