Mumps

1. Causative Organism
2. Clinical Signs, Symptoms and Complications
3. Method of Transmission
4. Public Health Significance
5. Prevention - Non Immunisation Methods
6. Prevention - Immunisation
7. Vaccine/s and Vaccination
8. Efficacy and Effectiveness
9. Availability Dosage and Administration
10. Indications and Recommendations
11. Adverse Events
12. Contraindications
13. Risks vs Benefits

Causative Organism

Mumps is a paramyxovirus with a single stranded RNA genome. It is rapidly inactivated by heat, formalin and ultraviolet light. Humans are the only known hosts.

Signs and Symptoms

In children, mumps is usually a mild disease (under 2 yrs of age it may be a sub-clinical illness); adults may have more serious disease and more complications.

Early symptoms are uncommon but may include fever, loss of appetite, muscle and joint aches, and headaches. Temperature is moderately high, usually lasting for 3-4 days. Swelling of the glands under and in front of the ear usually starts on one side and then progresses to the other side rapidly. Swelling may last from 7-10 days. Eating or drinking acidic or citric foods causes much discomfort.

Case fatality rates are 1.8 per 10,000 overall and 1.4% for mumps encephalitis.

Mumps is diagnosed by a combination of symptoms, physical signs and laboratory confirmation of the virus, as not all cases develop characteristic parotitis and not all cases of parotitis are caused by mumps.

Complications include:

• Meningitis (with headache and stiff neck) occurs in up to 15% of people with clinical mumps, but usually resolves without any permanent damage.
  
• Up to 50% of post-pubertal males experience "orchitis," or testicular inflammation, as a complication of mumps. This may involve pain, swelling, nausea, vomiting, and fever, with tenderness of the area possibly lasting for weeks. Sterility is a rare complication.
  
• Post-pubertal females may experience oophoritis.
  
• An increase in spontaneous abortion (miscarriage) has been found among women who developed mumps during the first trimester of pregnancy; there is no evidence that mumps causes birth defects.
  
• Profound sensori-neural deafness, in one or both ears, can occur in approximately one per 15,000 reported cases of mumps.
  
• Other complications include pancreatitis, neuritis, arthritis, mastitis, nephritis, thyroiditis and pericarditis.
  
• Mumps may cause aseptic meningitis (1 in 400 to 1 in 6000).
  

Child very swollen under the jaw and in the cheeks due to mumps. Courtesy of Centers for Disease Control and Prevention

Method of Transmission

• Spread from person to person through the air (by coughing, sneezing and direct contact), but is less contagious than measles or chickenpox.
• The incubation period is 14-18 days, but can range from 14-25 days. The infectious period is considered to be three days prior to until four days following the onset of symptoms.
  
  
  

Public Health Significance

• Outbreaks of mumps can occur in highly vaccinated populations, which suggests that mumps transmission can be sustained among the few people who are not vaccinated.

New Zealand epidemiology

Between 1970 and 1991 there were 2002 hospital admissions for mumps, with an increase in the number of cases every three to four years. There was a mumps epidemic in 1994. There has not been an epidemic since then, presumably because of the introduction of the MMR immunisation in 1990 (Immunisation Handbook 2006, Ministry of Health).

Prevention  - Non Immunisation Methods

Mumps virus continues to circulate in most countries, so the chances of being exposed at some point are relatively high.
Exclusion of cases from daycare, school and work, as well as exclusion of unimmunised individuals during an outbreak may reduce but not eliminate  transmission. Vaccination has proved to be the only effective large-scale prevention method.

Prevention  - Immunisation

Mumps vaccine is produced from a live attenuated (weakened) strain (Jeryl Lynn) of mumps virus prepared in chick embryo cell culture. Monovalent preparations are available, but are not recommended due to problems with quality and consistency. The combination mumps-measles-rubella (MMR) vaccine is recommended.

A live vaccine based on the Urabe strain was withdrawn from most countries with developed economies in 1992 due to a finding of one UK study that estimated a  1 in 11,000 risk of mumps vaccine meningitis. Aseptic meningitis occurs in 1 in 800,000 doses following administration of the Jeryl Lynn strain of mumps vaccine which is used in most MMR vaccines now. MMR vaccines are widely available and recommended by the WHO.

Efficacy and Effectiveness

• More than 95% of people who receive one dose of Mumps/MMR vaccine develop antibodies. Clinical evidence extending for more than 25 years indicated that vaccine-induced immunity is long lasting.
• Two doses are generally recommended to ensure that those who miss out on or don't respond to the first dose receive a second dose.
• Vaccination against mumps after exposure to the virus will not help prevent disease if the child has already been infected. However, if the child did not become infected after this particular exposure, the vaccine will help protect him or her against future exposure to mumps.

Availability

• MMR is given in New Zealand as MMR II^® and is part of the routine schedule.
• MMR vaccine is widely available in most countries and is recommended by the WHO. 

Dosage and Administration

• MMR II^® is given at fifteen months and four years of age.
• Mumps vaccine, as in MMR vaccine, is usually administered as a subcutaneous injection (Intramuscular administration however is still immunogenic). It is a powder that must be reconstituted before it can be used. Dosage is 0.5 mL.
• There is no medical reason to give the components of MMR separately. Indeed, until the child has had all three components, they remain at risk of catching any of the 3 diseases that they have not yet been vaccinated against.
• Mumps /MMR vaccine is routinely given in 2 doses. The first is generally given after age 12 months as maternal antibodies circulating in the infant may inactivate vaccine given to younger infants. The second dose is given at least 4 weeks after the first. In many counties this is now given around the age of school entry.
• There is no hazard in vaccinating those who are already immune to one or two components and circulating antibody simply inactivate the vaccine components.
• If it is necessary to give the vaccine to a child under 12 months because they are at special risk, the child should receive a second dose at 15 months and a further booster dose at the normal time.
  

Indications and Recommendations

• Primary immunisation. All infants and non-immune individuals aged 12 months and over should receive a 2-dose primary immunisation course. The first dose is given at 12-15 months. Most countries give the second dose at school entry. For catch-up immunisation programmes, the interval between doses may be shortened to 1 month.
• Health care workers and daycare staff to prevent transmission of mumps virus. MMR immunisation is recommended for health care workers to reduce the risk of transmission of mumps and rubella viruses in similar settings.
• International travellers. Most countries recommend immunisation for all international travellers 9 months or over who were born after 1965. At least one and preferably 2 doses should be given.
• Household and intimate contacts of those with immunosuppression to provide “ring-fence” protection. No evidence of risk exists for transmission of the vaccine virus .
• Outbreak control. Exclusion of cases from daycare, school and work, as well as exclusion of unimmunised individuals during an outbreak may reduce but not eliminate transmission.
• Immunisation is recommended one time for all persons born after 1960 who lack evidence of immunity to measles (receipt of live vaccine on or after the first birthday, laboratory evidence of immunity, or a history of physician-documented measles).
• Those born prior to 1960 are almost certain to have been exposed to measles, and are therefore unlikely to require measles immunisation.

Adverse Events

• Malaise, fever and/or rash may occur after MMR vaccination; most commonly 7-10 days post vaccination.
  About 1/10 have discomfort or local inflammation.
• The rash which is non-infectious occurs in about 1/100 recipients.
  
• Transient joint symptoms (from the rubella component) are quite common, occurring in 1 in every 35 children. In adults about 15% may get temporary joint pain from the rubella vaccine virus.
  
• Rare complications include thrombocytopaenia occurring in 1 in every 35,000 children. Spontaneous recovery without treatment is usual.
  
• Aseptic meningitis occurs in 1 in every 100,000 children given the vaccine, and is related to the mumps component of the vaccine. Children recover completely.
  
• Encephalitis occurs in 1 in every million children given the vaccine. In most cases this is more likely to be a chance occurrence and not caused by the vaccine.
  
• Anaphylaxis occurs at less than 1 per million doses.
  
• No association has been established between MMR and autism, Crohn’s disease or ADHD.
  

Contraindications

• Anyone who has had an anaphylactic reaction to a previous dose or any component of the measles vaccine should not be given another dose.
• Live attenuated measles vaccine should not be given to pregnant women or those with severe congenital or acquired immune disorders (can be given for HIV infection).
• Recipients of human immunoglobulin or whole blood transfusion within the last 3-12 months.
• Receipt of a dose of a live vaccine less than 4 weeks prior to measles immunisation.
• Anyone with untreated malignant disease, or those who present with an acute febrile illness.
  

Risks vs Benefits

Disease	Risks of disease	Risks of vaccine
Mumps – a highly contagious viral infection spread by saliva. Causes parotid swelling and fever.	Aseptic meningitis 15 per 100. Orchitis in 20% of post-pubertal males and oophoritis in 5% of post-pubertal females.  Rarely, sterility may occur. Encephalitis (1 per 400 to 1 per 6000). Mortality in these individuals of 1.4%. Overall case fatality rate of 1.8 per 10,000. Mumps contracted during pregnancy increases the risk of miscarriage.	Mild local or systemic reaction (14.2%) Arthralgia (2.8%) Aseptic meningitis (1 per 100,000) Encephalitis (1 per million) Anaphylaxis (<1 per million)

• Link to Immunisation Handbook (2006) Chapter 10 - Mumps