Perceptions of mumps and MMR vaccination among university students in England: an online survey

Mumps is easily preventable through vaccination. Investigation of a number of recent mumps outbreaks in universities in the North West of England, however, found that affected students were either not vaccinated or only partially vaccinated. An online survey of students (n=2456) attending five universities in the region was undertaken during 2010 to establish MMR vaccination status, knowledge of mumps and willingness to take up vaccination if offered. Regression analysis was undertaken to identify characteristics of unimmunized students to ascertain likely target groups for future vaccination campaigns. Students least likely to be fully vaccinated with MMR included males; those not registered with a GP; first year students; mature students; and those with poor knowledge of mumps. A high proportion of students were willing to accept MMR vaccination if offered at university. Those least likely to take up vaccination included students not registered with a GP; mature students; and those who did not consider mumps to be a serious disease. The survey also highlighted that misconceptions remain about both the MMR vaccine safety and perceptions of risk/benefit of the vaccine. Encouraging registration with a GP and awareness raising should be a key part of campaigns to improve vaccination uptake among university students.     

Mumps increase in Flanders,Belgium, 2012–2013: Results from temporary mandatory notification and a cohort study among university students

Introduction

In 2012, an increase in mumps notifications occurred in Belgium, affecting young vaccinated adults. At the end of 2012, a mumps outbreak occurred at the Catholic University of Leuven KU Leuven in Flanders. We investigated the outbreak to estimate incidence, mumps vaccine effectiveness and to detect potential risk factors for the disease.

Methods

In June 2012, we set up mandatory notification in Flanders and we collected information on circulating genotypes from the National Reference Centre. We conducted a cohort study among KU Leuven students. We defined a case as self-reported parotitis, between September 2012 and March 2013. We distributed web-based questionnaires to a random sample of students. We calculated vaccine effectiveness by comparing the risks in students vaccinated twice with those vaccinated once. We estimated risk ratios (RR) to identify risk factors.

Results

From 16th June 2012 to 1st April 2013, 4061 mumps cases were notified to the regional public health office (30% were vaccinated once and 69% were vaccinated twice). All 16 samples collected at the KU Leuven were genotype G5. Of 717 participants of the cohort study, 38 (5%; 95%CI 4–8%) met the case-definition. All reported being vaccinated with at least one dose of mumps-containing vaccine. The incidence of mumps was 5% among those vaccinated twice and 16% among those vaccinated once (vaccine effectiveness of two doses compared to one: 68%, 95%CI −24% to 92%). The risk of mumps was lower among those vaccinated with two doses of mumps-containing vaccine ≤10 years before (RR: 0.33, 95%CI 0.10–1.02) and higher among students working in a bar (RR: 3.6, 95%CI 1.8–7.0).

Conclusions

Incomplete protection by two doses of mumps-containing vaccine, possible waning immunity and intense social contacts may have contributed to the occurrence of this outbreak in Flanders. Efforts to maintain high vaccination coverage with two doses remain essential. However, the reasons for low vaccine effectiveness must be further explored and additional immunological research for more immunogenic mumps vaccines is necessary.     

Outbreak of measles in medical students and determination of immune status to measles-mumps-rubella viruses

We conducted an investigation after a measles outbreak in medical students to determine the immunity of the medical students, the correlation between history and seropositivity, and measles-mumps-rubella vaccine effectiveness. After a preliminary study done during measles outbreak, a cross-sectional study was planned. Serum samples from 322 medical students were tested by enzyme-linked immunosorbent assay, vaccinated volunteers, then re-tested vaccinees. Histories of measles, mumps and rubella were taken. Of 322 students, seven students (2.2%) were seronegative to measles, 13 (4.0%) to mumps, and 13 (4.0%) to rubella. Historical information revealed 30.4% of sensitivity in measles and 34.3% in mumps, whereas 5.2% in rubella. Among those seronegative on admission and vaccinated, seroconversion rates were 100% (5/5), 90.9% (10/11), 100% (8/8) in measles, mumps and rubella vaccine, respectively. Of 265 vaccinated students parotitis was detected in one female student, arthralgia was observed in three students (1.1%) and myalgia in two (0.7%), and 240 students reported no side effects. We detected the unreliable historical screening and high seroprevalence of measles, mumps and rubella in prevaccine era for mumps and rubella and, safety of MMR vaccination in medical students in Turkey.     

Effectiveness of Rubella vaccine in a rubella outbreak in Guangzhou city,China, 2014

BackgroundWHO recommends the use of rubella-containing vaccine (RCVs) to prevent rubella and congenital rubella syndrome (CRS). Most licensed rubella vaccines in use globally are based on RA27/3 strains and have estimated vaccine effectiveness (VE) rates of 95–100%. In contrast, China uses a BRD-II strain-based rubella vaccine. Few field studies have been conducted that estimate VE of China's RCV. On March 17, 2014, a rubella outbreak was reported in a middle school in Guangzhou city, China. We conducted an investigation to understand reasons for the outbreak, and we used that investigation to estimate vaccine effectiveness of China's rubella vaccine.MethodsTo identify cases, investigators reviewed records kept by the school doctor and absentee records kept by teachers. Self-administered questionnaires were sent to parents of all students to collect information about the students’ symptoms, the results of any physician consultation, and disease history. We obtained demographic information and illness information for all students in the school; vaccination status was determined by inspection of official, parent-held vaccination records. A retrospective cohort study was conducted in 13 classes that had secondary cases of rubella. Using the secondary attack rates, we evaluated VE by the number of RCV doses received and age at vaccination.ResultsDuring the period February 17–May 23, 2014, 162 students (50 suspected cases, 88 probable cases, 24 confirmed cases) were diagnosed with rubella, yielding an overall attack rate of 10% (162/1621). Cases occurred in 27 classes (73%) of 37 classrooms. Secondary cases occurred in 13 classes (35%) of 37 classrooms. A total of 1130 students (69.7%) have vaccination certificates; 419 (37%) students were record-confirmed to have received RCV. For those vaccinated using BRD-II strain vaccine, vaccine effectiveness (VE) was 94% (95%CI: 75–98). VE for measles, mumps, and rubella (MMR) vaccine which is based on either BRD-II or RA27/3 strain was 89% (95%CI: 56–97). VE of a single dose of domestic monovalent rubella vaccine that used BRD-II strain vaccine was 93% (95%CI: 73–98). VE for those who received the vaccine between 1 and 2 years of age was 95% (95% CI: 67–99) while the VE was 100% for those vaccinated after 2 years of age. VE among those who received RCV <12 years ago was 100% while VE among those who received RCV ≥12 years ago was 92% (95%CI: 70–98).ConclusionsThe rubella vaccines used in China that are based on the BRD-II rubella vaccine strain have VE of 94%, which is similar to the more commonly used RA27/3-based RCVs. Low vaccination coverage contributed to this outbreak; early reporting of an outbreak is necessary for effective outbreak response immunization.     

麻疹-流行性腮腺炎-风疹联合减毒活疫苗流行性腮腺炎组份免疫效果观察

目的对麻疹-流行性腮腺炎（流腮）-风疹联合减毒活疫苗（Measles,Mumps and Rubella Combined Atteruated Live Vaccine,MMR）中,流腮组份的免疫效果进行观察评价。方法对接种MMR后,流腮组份免疫学效果进行分析评价,并追踪观察记录2年内受种人群及本地人群中流腮发病情况。结果接种MMR前,流腮抗体几何平均滴度（Geometric Mean Titer,GMT）为1∶6.87,免疫后GMT为1∶26.35,免疫后GMT是免疫前GMT的3.8倍,免疫前、后GMT差异有统计学意义（Z=-6.22,P〈0.001）。免疫前、后流腮抗体阳性率分别为64.63%、95.12%,差异有统计学意义（χ2=23.71,P〈0.001）。免疫前、后流腮抗体阴性者与阳性者GMT和免疫前相比差异均有统计学意义（Z=-4.40,P〈0.001;Z=-4.84,P〈0.001）。免疫前流腮抗体阴性者与阳性者接种MMR后,免疫成功率分别为86.21%、54.72%,差异有统计学意义（χ2=8.266,P=0.004）。对受种人群及本地人群进行为期2年的流腮发病追踪观察,在受种人群中未发现流腮病例报告。结论在3-6岁儿童中接种MMR,对于预防流腮效果良好,产生的保护效果至少能维持2年。     

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 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.     

A measles outbreak at a college with a prematriculation immunization requirement.

BACKGROUND. In early 1988 an outbreak of 84 measles cases occurred at a college in Colorado in which over 98 percent of students had documentation of adequate measles immunity (physician diagnosed measles, receipt of live measles vaccine on or after the first birthday, or serologic evidence of immunity) due to an immunization requirement in effect since 1986. METHODS. To examine potential risk factors for measles vaccine failure, we conducted a retrospective cohort study among students living in campus dormitories using student health service vaccination records. RESULTS. Overall, 70 (83 percent) cases had been vaccinated at greater than or equal to 12 months of age. Students living in campus dormitories were at increased risk for measles compared to students living off-campus (RR = 3.0, 95% CI = 2.0, 4.7). Students vaccinated at 12-14 months of age were at increased risk compared to those vaccinated at greater than or equal to 15 months (RR = 3.1, 95% CI = 1.7, 5.7). Time since vaccination was not a risk factor for vaccine failure. Measles vaccine effectiveness was calculated to be 94% (95% CI = 86, 98) for vaccination at greater than or equal to 15 months. CONCLUSIONS. As in secondary schools, measles outbreaks can occur among highly vaccinated college populations. Implementation of recent recommendations to require two doses of measles vaccine for college entrants should help reduce measles outbreaks in college populations.     

Mumps outbreak in a highly vaccinated student population,The Netherlands, 2004

In September 2004 a mumps outbreak occurred at an international hotel school in The Netherlands. We investigated this outbreak to identify risk factors for mumps. There were 105 mumps cases (overall mumps attack rate (AR) 12% (95% CI: 10–15%)). The AR for Dutch vaccinated and unvaccinated participants was 12% (95% CI: 10–15%) and 15% (95% CI: 3–42%), respectively. Independent risk factor was mumps contact. Explanations for the relatively high AR among vaccinated participants include primary vaccine failure, waning immunity and incomplete vaccine-induced immunity in the context of high mumps virus exposure in a school party and a crowded boarding school.     

Prevalence of mumps antibodies in the Israeli population in relation to mumps vaccination policy and incidence of disease

We examined the prevalence of mumps antibodies in the Israeli population in relation to mumps vaccination policy and past and subsequent incidence of disease. The levels of specific IgG antibodies against mumps were tested in 3330 residual sera collected during 1997-1998 from an age-stratified population sample. Against the background of a consistent MMR vaccination coverage of >90%, the age- and sex-adjusted seropositivity to mumps was 77.0%. No significant differences between genders were found. Seropositivity in the 10-13 years age group, born just before the introduction of the MMR vaccine, was the lowest (59%). These birth cohorts were the target of an outbreak of mumps in 2005 that occurred among high-school students and military recruits. A trend of waning immunity was observed between the first and second vaccine doses. The seroepidemiological data demonstrate that immunity levels below the herd immunity threshold, along with social mixing and crowded conditions facilitated the occurrence of mumps outbreaks. Periodical serosurveys are an essential component in the evaluation of the vaccination policy against mumps.     

Mumps Postexposure Prophylaxis with a Third Dose of Measles-Mumps-Rubella Vaccine,Orange County,New York,USA

Although the measles-mumps-rubella (MMR) vaccine is not recommended for mumps postexposure prophylaxis (PEP), data on its effectiveness are limited. During the 2009–2010 mumps outbreak in the northeastern United States, we assessed effectiveness of PEP with a third dose of MMR vaccine among contacts in Orthodox Jewish households who were given a third dose within 5 days of mumps onset in the household’s index patient. We compared mumps attack rates between persons who received a third MMR dose during the first incubation period after onset in the index patient and 2-dose vaccinated persons who had not. Twenty-eight (11.7%) of 239 eligible household members received a third MMR dose as PEP. Mumps attack rates were 0% among third-dose recipients versus 5.2% among 2-dose recipients without PEP (p = 0.57). Although a third MMR dose administered as PEP did not have a significant effect, it may offer some benefits in specific outbreak contexts.     

A novel measles outbreak control strategy in the Netherlands in 2013–2014 using a national electronic immunization register: A study of early MMR uptake and its determinants

BackgroundDuring a large measles outbreak in the Netherlands in 2013–2014, infants aged 6–14 months living in municipalities with low (<90%) measles-mumps-rubella (MMR) coverage were individually invited for an early MMR using the national electronic immunization register, Præventis. We estimated uptake of early MMR prior to and during the 2013–2014 outbreak and assessed determinants for early MMR vaccination.MethodsWe obtained vaccination records from Præventis, and defined early MMR as vaccination before 415 days (13 months) of age. A multi-level multivariable logistic regression model, restricted to infants with three diphtheria-pertussis-tetanus-polio (DPTP) vaccinations was used to examine the association between early MMR uptake and sex, parents’ country of birth, socioeconomic status (SES; at postcode level) and voting proportions for the Reformed Political Party (SGP; at municipal level), used as a proxy for religious objections towards vaccination.ResultsIn the 29 municipalities with low MMR coverage, uptake of early MMR was 0.5–2.2% prior to the outbreak. Between July 2013 and March 2014, 5,800 (57%) invited infants received an early MMR. Among infants with three DPTP, 70% received an early MMR. Only 1% of infants without prior DPTP received an early MMR. Lower early MMR uptake was associated with a higher SGP voter-ship (OR 0.89 per 5% increase, 95%CI 0.83–0.96), parents’ with unknown country of birth (OR 0.66 95%CI 0.47–0.93) and compared with very high SES, high SES had significantly lower early MMR uptake (OR 0.66 95%CI 0.50–0.87).DiscussionThis is the first study describing use of Præventis during an outbreak and to assess determinants of early MMR uptake. More than half of invited infants obtained an early MMR. SES, parents’ with unknown country of birth and religious objections towards vaccination were found to be associated with lower early MMR uptake. In future outbreaks, these determinants could be used to tailor intervention strategies.     

Mumps vaccine effectiveness in highly immunized populations

The aim of the study was to investigate effectiveness of mumps MMR component in communities with high MMR coverage. Outbreak-related cases of mumps born between 1995 and 2005 notified to Navarre and Catalonia public health services during the period 2005–2007 were studied. Vaccine effectiveness (VE) and their 95%CI were calculated using the screening method. Of 47 confirmed, 85.1% immunized with at least one dose (1MMR) and 44.9% with two (2MMR). Estimated VE was 85.4% (95%CI: 67.3–93.4) for 1MMR and 88.5% (95%CI: 78.1–93.9) for 2MMR. High 2MMR coverage, improved confirmation techniques and further VE studies with all confirmed cases are needed to prevent further outbreaks.     

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.     

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.     

The risk of aseptic meningitis associated with the Leningrad-Zagreb mumps vaccine strain following mass vaccination with measles-mumps-rubella vaccine,Rio Grande do Sul,Brazil, 1997

BACKGROUND: Few data are available on the risk of aseptic meningitis following vaccination with the Leningrad-Zagreb (L-Z) strain of mumps vaccine. In 1997 the mumps vaccine was introduced into the state of Rio Grande do Sul in Brazil through mass vaccination with mumps-measles-rubella (MMR), targeting children aged 1-11 years. Five municipalities used exclusively MMR vaccine containing the L-Z strain of mumps. An outbreak of aseptic meningitis was observed shortly after the mass campaign. METHODS: To estimate the risk of aseptic meningitis associated with this strain, we analysed vaccination and meningitis case surveillance data from the selected municipalities. A case of vaccine-associated aseptic meningitis was defined as one with a pleocytosis of 10-1,500 leukocytes/ml and occurring within 15-35 days after vaccine receipt. RESULTS: We estimated a risk of 2.9 cases per 10,000 doses of L-Z administered, equivalent to 1 case per 3,390 doses administered. The overall risk of aseptic meningitis following the campaign was increased 12.2-fold (95% CI: 6.0-24.7) compared with the same period in 1995-1996. Following the mass campaign, the incidence of mumps declined 93% during 1998-2000. CONCLUSIONS: Vaccination with the L-Z strain of mumps vaccine as part of a mass campaign was associated with a significantly increased risk of aseptic meningitis. Decisions about type of mumps vaccine and mumps vaccination strategies must consider vaccine safety issues in addition to other criteria.     

Epidemic of complicated mumps in previously vaccinated young adults in the South-West of France

ObjectiveWe report the features and diagnosis of complicated mumps in previously vaccinated young adults.Patients and methodsWe retrospectively studied 7 cases of complicated mumps managed during 1 year at the Bordeaux University Hospital. The diagnosis was suggested by the clinical presentation and confirmed using specific RT-PCR.ResultsFive cases of meningitis, 1 of orchitis, and 1 of unilateral hearing impairment were identified. Each of the 7 patients had been previously vaccinated with MMR, 4 had received 2 doses of this vaccine. Blood tests revealed high rates of IgG antibodies, usually considered as sufficient for immunological protection, and every patient had at least 1 positive RT-PCR test for mumps.ConclusionOutbreaks of complicated mumps may still occur despite a broad coverage of MMR vaccination. The clinical presentation suggested mumps but the final diagnosis could only be confirmed by genomic detection of the virus. Unusual viral strains with increased neurovirulence, insufficient population coverage associated with immunity decrease over time may explain outbreaks of complicated mumps. A full vaccine scheme of contact people or a third injection of vaccine for previously vaccinated people who are at risk of developing mumps are required to prevent further spreading of the disease during the outbreak.     

A population-based case–control study on viral infections and vaccinations and subsequent multiple sclerosis risk

Viral infections are probably involved in the pathogenesis of multiple sclerosis (MS). A recent cohort study in the Gothenburg population revealed no change in MS incidence associated with the introduction of the Swedish measles, mumps and rubella vaccination programmes. The aim of the present study was to clarify whether these infections or vaccinations, and two other infections, varicella and infectious mononucleosis, influence MS risk. We performed a population-based case–control study in Gothenburg that included 509 MS cases and 2,067 controls, born 1959–1986. Data on infections and vaccinations were obtained from questionnaires and from child health and school health records. We found no significant associations between measles, mumps, rubella or varicella and MS risk. These results were consistent between the two source materials. Infectious mononucleosis was associated with significantly higher MS risk (odds ratio 2.03, 95% CI 1.52–2.73). Overall, there was no significant association between measles-mumps-rubella (MMR) vaccination and MS risk, while those MMR vaccinated before age ten only were at significantly higher MS risk (odds ratio 4.92, 95% CI 1.97–12.20). Those MMR vaccinated both before and after age ten had intermediate MS risk. Infection with measles, mumps, rubella and varicella did not influence MS risk in contrast to infectious mononucleosis which conferred doubled MS risk. The association with ‘early’ MMR vaccination only was an isolated finding, limited by a small number of subjects and multiple testing. Most likely this was a chance finding. Future studies could investigate it on an a priori basis.     

Isolation compliance among university students during a mumps outbreak, Kansas 2006

A large mumps outbreak occurred among students at a Kansas university in 2006. To reduce transmission, students with mumps were asked to isolate themselves. We describe isolation measures and student compliance with these measures. Questionnaires were administered to students suspected of having mumps. Of the 132 students instructed to stay isolated, 75% stayed isolated for the number of days recommended and were considered compliant. Case-students told to stay isolated for 1-4 days were more likely to be compliant [86% vs. 66%; adjusted odds ratio (aOR) 3.6, 95% CI 1.4-9.0] than those told to stay isolated for 5-9 days. Those who rated avoiding contact with others during isolation as very important were also more likely to be compliant (83% vs. 60%; aOR 3.6, 95% CI 1.5-8.4) than those who rated the importance lower. In a college setting, it may be difficult to achieve high compliance with guidelines recommending that persons stay isolated for much longer than 4 days.     

2005-2008年攀枝花市西区流行性腮腺炎流行病学分析

目的了解攀枝花市西区流行性腮腺炎（流腮）流行病学特征及发生原因,为控制流行性腮腺炎提供科学依据。方法利用法定传染病报告系统疫情资料和流腮暴发疫情流行病学个案调查资料,分析西区流行性腮腺炎流行病学特征。结果2005-2008年攀枝花市西区报告本地区流腮病例672例,年平均发病率99.74/10万;发病年龄以5～14岁最多,占74.40%（500/672）;职业以学生最多,占64.14%（431/672）;发病月份以3～7月居多,占67.71%（455/672）,各街办均有发病。共发生暴发疫情4起（2005年1起,2008年3起）,发病181例;无免疫史和免疫史不详者发病率高于有免疫史者（P〈0.01）,无免疫史者发病率高于免疫史不详者（P〈0.01）,免疫史超过5年者发病率高于少于5年者（P〈0.01）。结论攀枝花市西区流行性腮腺炎发病率较高,有暴发疫情发生;疫苗接种率低,易感人群积累是造成流行性腮腺炎暴发的主要原因。