Information for Health Professionals

Mumps in Canada, 2007

As of March 5, 2008, 1,284 confirmed cases of mumps have been reported in 2007 from ten out of 13 Canadian provinces and territories. (Table 1, Figure 1) Confirmed cases are either laboratory-confirmed OR clinically compatible and linked to a laboratory-confirmed case. There have been on-going outbreaks centred in the Maritime provinces and in the province of Alberta. In addition, several other provinces experienced increased mumps activity in 2007.

Table 1: Geographical and Sex Distribution of Confirmed* Mumps Cases Reported in Canada
Onset December 31, 2006 – December 29, 2007 (N=1,284)

Figure 1: Confirmed* Mumps Cases in Canada
Epi-Year 2007 (Onset December 31, 2006 to December 29, 2007 (n=1,219**)

*   A confirmed case is either a laboratory-confirmed case OR clinically compatible and linked to a laboratory-confirmed case.
** Remainder of the total 900 cases are pending or missing dates of onset.

It is assumed that most people born before 1970 (approximately 40 years old) are immune to mumps as they were likely naturally exposed to the mumps virus in the period before immunization significantly reduced the amount of mumps virus that was circulating. Most people born between 1990 and 1994 (12 and 17 years old depending on the province/territory of residence) were offered 2 doses of mumps-containing vaccine due to the introduction of a second dose of measles-mumps-rubella (MMR) vaccine for measles control in 1996-97 in most provinces and territories. This has left a susceptible cohort of people born between 1970 through 1990 (to a lesser extent through 1994) who were only eligible for one dose of mumps-containing vaccine and who are not assumed to have natural immunity (Figure 2). It is important to note, that the age at which natural immunity to mumps can be assumed is not known with certainty and that some individuals born prior to 1970 may still be susceptible to mumps.

Figure 2: Mumps-Containing Vaccine Coverage by Birth Cohort

The majority of cases (58%) reported in 2007 occurred in persons aged 20-29 years. (Figure 3) For those cases where information was reported (n=594), 50% were post-secondary students. The reason for the particular susceptibility among those who are college and university-aged is multifactorial. They are too young for natural immunity and too old for routine two-dose MMR immunization. Mumps has a fairly long infectious period (up to 16 days), a long incubation period (14 to 25 days) and up to 20% of infectious cases show no signs or symptoms. In addition, the very social and mobile lifestyles of this age group appear to be facilitating disease transmission and interfering with control measures. This age group tends not to adhere to isolation requests and they generally do not participate when immunization is offered. Furthermore, post-secondary students often share living/sleeping arrangements, many are involved competitive sports, they frequent bars/pubs/nightclubs as well as travel during school holidays and breaks. Additional cases in this demographic group and possibly other jurisdictions would not be unexpected.

Of those mumps cases reported in 2007 with known immunization history (n=586), 8% (45) had received 2 or more doses, 73% (430) had received one dose and 19% (111) received no doses of mumps-containing vaccine.

The data on mumps hospitalizations and complications are incomplete. Complications have been reported in approximately 8% of cases in 2007. There have been reports of orchitis (76), oophoritis (9), hearing loss (8), mastitis (3), meningitis (1), encephalitis (1), pancreatitis (1) and nephritis (1). Less than 2% of cases have resulted in hospital emergency department visits, overnight observation or hospital admission.

Immunization

Mumps remains endemic in many countries throughout the world. Mumps vaccine is used in only 57% of World Health Organization member countries; predominantly in countries with more developed economies. 

The Public Health Agency of Canada encourages parents, guardians and adults to maintain up-to-date immunizations for themselves and their children.

The National Advisory Committee on Immunization (NACI) provides the Public Health Agency of Canada with ongoing and timely medical, scientific and public health advice relating to immunization. NACI released their updated recommendations for mumps-containing vaccine in August 2007. They recommend two doses of the measles-mumps-rubella (MMR) vaccine for infants and children. In addition, they recommend a second dose of MMR vaccine for certain high-risk adults born in or after 1970 who have not received two doses of the vaccine and are possibly susceptible to the mumps virus. This includes students in secondary and post-secondary institutions and health-care workers. All NACI guidelines can be accessed on the Public Health Agency of Canada's website (www.naci.gc.ca).

Individual provinces and territories implement immunization programs within their respective jurisdictions according to local need and decision processes. The 2004 National Immunization Coverage Survey (NICS) found that 94% of Canadian children had received a single dose of the MMR vaccine by their second birthday. Coverage estimates for the second dose of MMR vaccine by 7 years of age was 79%. Other results from the 2004 National Immunization Coverage Survey can be found in the Canadian National Report on Immunization. The recent outbreaks and increases in mumps cases across Canada have led to targeted immunization activities in several provinces and territories (Table 2).

On December 11, 2007, Health Canada advised provincial and territorial health authorities not to use three lots of measles-mumps-rubella vaccine while the Department investigated six suspected cases of anaphylaxis in Alberta patients. All anaphylactic events were associated with the same lot number and involved young adults who had a previous history of allergy. All the individuals recovered upon treatment. The vaccinations took place during a catch-up campaign for young adults in response to a mumps outbreak. The review found no link between the vaccine lot and the adverse events in Alberta. The suspensions have been lifted and the lots are available for use by provinces and territories to vaccinate adults and children. (http://www.hc-sc.gc.ca/ahc-asc/media/advisories-avis/_2008/2008_35_e.html)

Table 2: Provincial and Territorial recommendations for mumps-containing immunization, 2007

British Columbia	Advising post-secondary students attending school in Nova Scotia or New Brunswick to ensure up-to-date immunization
Alberta	Immunizing post-secondary students and all individuals 17-26 years of age starting in 2007 but was suspended on December 11, 2007
Saskatchewan	Immunizing grade 12 students starting in 2007-2008. Advising post-secondary students attending college or university in Nova Scotia, New Brunswick or Alberta to ensure immunization is up-to-date
Manitoba	No additional recommendations/postings
Ontario	Advising students attending school in Nova Scotia and New Brunswick and those traveling to these provinces to ensure immunization is up-to-date
Quebec	No additional recommendations/postings
New Brunswick	Immunizing: grade 12 students starting in 2007 (for a six year period); health care workers, born in or after 1970 who do not have proof of 2 doses of the MMR vaccine or proof of immunity, will be offered one dose starting in 2007 (for a one year period)
Nova Scotia	Immunizing post-secondary students and grade 11 and 12 students, who have not already received two doses, starting 2007-2008
Prince Edward Island	Immunizing post-secondary students and faculty and staff born after 1970 who have not received 2 doses of the MMR vaccine starting in 2007
Newfoundland Labrador	No additional recommendations/postings
Northwest Territories	No additional recommendations/postings
Yukon Territory	Immunizing individuals born after 1970 without documentation of any MMR doses and with no memory of having had mumps as well as those with documentation of having had only one dose of the MMR vaccine
Nunavut	Immunizing grade 12 students starting in 2007-2008

Source: Information in this table was provided by the provinces and territories through the Canadian Immunization Committee (November 2007) and through recent web-postings (web links, where available, are provided). Readers should refer to their local department of health and/or their provincial/territorial ministry of health for details on immunization schedules and programs.

Laboratory Testing and Viral Strain

The clinical and laboratory diagnosis of mumps can be difficult. Proper specimen collection and transportation along with appropriate laboratory testing and cautious interpretation of results are important. In 2007, the Public Health Agency of Canada's National Microbiology Laboratory revised their laboratory guidelines for the diagnosis of mumps. The guidelines are available on the Public Health Agency of Canada's website (www.nml-lnm.gc.ca/english/mumps.htm)

Identifying virus strains is useful for differentiating vaccine and wild-type strains, linking cases, linking outbreaks, tracking importations and documenting the elimination of a particular strain from a geographic area. The viral strain in the two 2007 Canadian outbreaks (Maritimes and Alberta) is identical to the genotype G strain detected from the 2005-2006 Nova Scotia outbreaks, the United States' multi-state outbreak in 2006 and the United Kingdom epidemic (2004-2006). In the United States' outbreak, there were over 2,500 cases reported in at least 13 states. It involved several university and college campuses and the median age was 21 years. In the United Kingdom, the epidemic peaked at more than 50,000 notifications, with the majority being 15-24 years old.

The G genotype is not unusual or rare and, like the rest of known genotypes of mumps, it has been circulating globally for decades or longer. There are multiple strains of the mumps virus and there is evidence that the immunity induced by one mumps virus strain protects against infection by other strains.¹⁰ However, there is also some evidence suggesting that the immune response directed against one genotype of mumps may not provide absolute protection against infection with mumps viruses of other genotypes.^11,12

Mumps virus detection, isolation and genotyping are available at the National Microbiology Laboratory.

Public Health Actions

Mumps cases are asked to self-isolate for a period of 9 days following the onset of symptoms.  The vaccine status of close contacts (i.e., household and intimate contacts/exchange of saliva) is assessed and updated so that they receive two doses of MMR vaccine. Guidelines have been put in place for health care workers who are cases or who are contacts of mumps cases.

Public health and primary care providers are encouraged to refer to their local or provincial/territorial ministry of health for specific recommendations on action that may be required within their jurisdiction.

All provinces and territories are being kept informed of the epidemiologic situation and the public health management strategies in the affected jurisdictions. Based on this, all jurisdictions are encouraged to continue monitoring mumps activity within their regions and report any changes and/or cases to the Public Health Agency of Canada, particularly in provinces and territories not currently affected by the on-going outbreaks.

The Public Health Agency of Canada along with the provinces and territories is developing national guidelines for mumps outbreak prevention and control. This group is drawing on the experiences and expertise both here in Canada and other countries.

Several provinces, territories and post-secondary institutions are encouraging students to ensure their immunization is up-to-date (readers should refer to specific provincial/territorial public health authorities and educational institutions).

The Public Health Agency of Canada will continue to provide updates on the current outbreak of mumps. The Agency is working with the affected provinces in monitoring this outbreak, providing technical advice and assisting with laboratory testing of clinical specimens at the National Microbiology Laboratory. The Public Health Agency of Canada supports the provincial outbreak response strategies that include the recommended isolation of cases and targeted immunization of contacts and susceptible cohorts.

The Public Health Agency of Canada recommends that jurisdictions experiencing outbreaks should consider offering an additional dose of MMR vaccine for immunization in outbreak settings. Some jurisdictions are encouraging and/or offering MMR vaccine to health-care workers and post-secondary students. In other jurisdictions, there are on-going discussions regarding an expanded immunization strategy to target the susceptible cohort. Readers should refer to their local or provincial/territorial ministry of health for specific recommendations.

The Public Health Agency of Canada encourages parents, guardians and adults to maintain up-to-date immunizations for themselves and their children, and encourages susceptible individuals to be immunized in accordance with the National Advisory Committee on Immunization (NACI) guidelines. All guidelines can be accessed at: www.naci.gc.ca. NACI currently recommends a second dose of the measles, mumps and rubella vaccine (MMR) for certain adults born after 1970. This includes students at post secondary institutions and health care workers.

Selected References

1. Epidemiology and Prevention of Vaccine-Preventable Diseases. Atkinson W, Hamborsky J, McIntyre L, Wolfe S, eds. 10th ed. Washington DC: Public Health Foundation, 2007, Centers for Disease Control and Prevention.
2. Canadian Immunization Guide. Seventh Edition. Ottawa, ON: Public Health Agency of Canada; 2006.
3. National Advisory Committee on Immunization: Statement on Mumps Vaccine. CCDR 2007; 33(8): 1-10.
4. Outbreak of Mumps Among Young Adults – Vancouver, British Columbia. CCDR 1997; 23(22).
5. Outbreak of Mumps, Montreal, October 1998 to march 1999 – With a Particular Focus on a School. CCDR 2000; 26(8).
6. Alberta Health and Wellness. Public health notifiable disease management guidelines. June 2005. URL: (http://www.health.gov.ab.ca/professionals/NotifiableDiseases.html)
   Accessed 23 Nov, 2007.
7. Watson-Creed G, Saunders A, Scott J, et al. Two successive outbreaks of mumps in Nova Scotia among vaccinated adolescents and young adults. CMAJ 2006; 175(5):483-8.
8. CDC. Measles, Mumps, and Rubella -- Vaccine Use and Strategies for Elimination of Measles, Rubella, and Congenital Rubella Syndrome and Control of Mumps: Recommendations of the Advisory Committee on Immunization Practices (ACIP). MMWR 1998; 47(RR-8); 1-57.
9. Jin L, Rima B, Brown D, et al.  Proposal for genetic characterisation of wild-type mumps strains: Preliminary standardisation of the nomenclature. Arch Virol 2005; 150; 1903-09.
10. Nojd J, Tesfaldet T, Samulesson, et al. Mumps virus neutralizing antibodies do not protect against reinfection with a heterologous mumps virus genotype. Vaccine 2001; 19: 1727-31.
11. Rubin S, Mauldin J, Chumakov K, et al. Serological and phylogenetic evidence of monotypic immune responses to different mumps virus strains. Vaccine 2006; 24; 2662–68.
12. Orvell C, Alsheikhly A, Kalantari M, et al. Characterization of genotype-specific epitopes of the HN protein of mumps virus. J Gen Virol 1997; 78: 3187-93.

Resources

For more information on mumps, please visit:

• Nova Scotia Department of Health Promotion and Protection
  or consult a public health professional.
• Nova Scotia's expanded mumps vaccination program
• National Advisory Committee on Immunization (NACI)
  Statement on Mumps Vaccine(NACI)
• National Microbiology Laboratory's guide to services and laboratory guidelines for the diagnosis of mumps
• Alberta Health and Wellness Mumps – News Release
• Alberta Suspends Mumps Immunization for Young Adults
• Alberta Disease Management Guidelines
• New Brunswick's expanded mumps vaccination program
• Prince Edward Island's mumps vaccine for post-secondary students
• Ontario Mumps Immunization Recommendations for College and University Students
• British Columbia Health Alert
• Government of Saskatchewan – News Release
• Public Health Agency of Canada Canadian National Report on Immunization, 2006
• Health Canada Warning – Three lots of measles, mumps, rubella vaccine suspended from use
• Review Determines Measles, Mumps and Rubella Vaccine Lots Can be Released for Use
• Publicly funded immunization programs in Canada