Measles

Causative Organism

Measles is a paramyxovirus, genus Morbillus. It is an RNA virus. Measles virus can survive for up to 2 hours in air, but is sensitive to heat, light and acidic pH.

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
10. Indications and Recommendations
11. Adverse Events
12. Contraindications
13. Risks vs Benefits

Signs, Symptoms and Complications

• Early symptoms include fever, runny nose, cough, loss of appetite, and conjunctivitis or "pink eye." Characteristic white Koplik’s spots may occur in the oral mucosa.
• After 3 to 5 days the rash appears at the hairline, moves to the face and upper neck, then proceeds down the body and usually lasts 4-6 days. 
• Measles is often a serious disease, with up to 30% of reported cases experiencing one or more complications. 
• Complications include:
  • Diarrhoea, Ear infections (7 %) and Pneumonia (6%), which accounts for 60% of measles-related deaths.
  • Acute encephalitis may develop in 1 in 1000 cases, of whom 15% die and a further 25% - 35% are left with permanent neurological damage.
  • Approximately 1 in 100,000 cases will develop subacute sclerosing panencephalitis (SSPE). This serious complication can lead to permanent brain damage.
  • Measles during pregnancy increases the risk of premature labour, miscarriage, and low-birth-weight infants, although birth defects have not been linked to measles exposure.
  • Measles can be especially severe in persons with compromised immune systems and immunisation for household contacts is important to protect them.
    

Measles rash covering child's arms and stomach. Courtesy of Centers for Disease Control and Prevention

Method of Transmission

• Measles is one of the most contagious viral diseases and can be transmitted from four days before until four days after the appearance of the rash.
• It is spread through the air by infectious droplets and is highly contagious.
• It takes an average of 10-12 days from exposure to the first symptom, which is usually fever.
• The measles rash doesn't usually appear until approximately 14 days after exposure, 3-5 days after the fever begins.
  

Public Health Significance

• Measles is endemic globally, although a few countries with developed economies have virtually eliminated wild measles virus. 
• Regular epidemics still persist in many countries.
• Developing countries have a higher burden on morbidity and mortality from measles.
• Measles has been earmarked as a candidate for elimination through the implementation of global mass immunisation programmes.

New Zealand Epidemiology

Summarised from 2006 New Zealand Immunisation Handbook. Ministry of Health.

• An epidemic was predicted in 1997, and an immunisation campaign was planned to prevent it. However, the epidemic began in April 1997, three months before the planned start of the campaign. The campaign was then brought forward so that 90–95 percent of cases were prevented 6. There were 2169 cases identified including 314 hospitalisations. There was one case of disease related measles encephalitis and no deaths. 
• Large scale measles epidemics occur when the number in the susceptible population increases and the immunisation coverage is low. It has been estimated that to prevent recurrent outbreaks of measles, 95 percent of the population must be immune. Since measles vaccine efficacy is 90–95 percent and not all children receive the first scheduled dose, the only way to achieve this level of immunity is by implementing a two dose immunisation strategy, as is now recommended.
• In 2000 a mathematical model was developed to estimate the future timing of measles epidemics in New Zealand. The results suggested that if no changes were made to the MMR schedule of 15 months and 11 years, the next measles epidemic would be between 2002 and 2004. Therefore from January 2001 the National Immunisation Schedule was changed to give the first dose of MMR at 15 months and the second dose at four years of age, prior to school entry.
• In 2005 the measles mathematical model was updated to calculate the effect of the measles catch-up in 2001 and to estimate the effect of changing the National Immunisation Schedule to give MMR at age 15 months and at age four years before school entry.
• As the incidence of measles decreases in New Zealand, it is important to continue high MMR immunisation coverage to lower the risk of imported measles causing outbreaks. Every suspected case of measles will need laboratory confirmation and characterisation to inform the local medical offi cer of health, so that public health control measures can be put in place.

Prevention - Non Immunisation Methods

• Measles is so highly infectious that immunisation is the only effective prevention.
• Exclusion of cases from daycare, school and work, as well as exclusion of unimmunised individuals during an outbreak may reduce but not eliminate transmission.
• If a child is exposed and has not been vaccinated, measles vaccine may prevent disease if given within 72 hours of exposure. Immune globulin (0.2-0.5 mL/kg IM) may prevent or lessen the severity of measles if given within six days of exposure.

Prevention - Immunisation

• Measles vaccine is produced from a live attenuated (weakened) strain (Edmonston or Schwarz strains) of measles virus prepared in chick embryo cell culture.
• The attenuated measles vaccine virus undergoes the infectious cycle in the host, triggering an immune response and the development immunity.

Availability

• MMR is given in New Zealand as MMR II^® at fifteen months and four years and is part of the routine schedule. 
• Monovalent measles and MR vaccines are not widely available. 
• Many manufacturers have ceased production, and are now making only MMR vaccine.
• MMR vaccines are widely available and recommended by the WHO.

Efficacy and Effectiveness

• More than 99% of people who receive two doses separated by at least 1 month, after their first birthday, develop serological evidence of measles immunity.
• Protection following a single dose occurs in 95% of vaccine recipients and is durable in most people.
• Two vaccinations, at least one month apart, are generally recommended to ensure that those who miss out on, or are unresponsive to the first dose, receive a second dose.

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 measles virus

• MMR immunisation is recommended for health care workers to reduce the risk of transmission of mumps and rubella virus in similar settings.

International travellers

• Most countries recommend immunisation of 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

• Should be offered 2 doses of MMR to provide “ring-fence” protection. No evidence of risk exists for transmission of the vaccine virus.

Outbreak control

• Measles immunisation is recommended for all individuals aged 6-9 months or over who may be susceptible to measles (primary course not commenced or completed, negative serology or uncertain immunisation history).
• 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.
• Parenterally administered live vaccines not administered on the same day should be administered at least 4 weeks apart whenever possible.
• 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
Measles – a highly contagious viral illness causing fever, cough and rash.	Otitis media (7%) Pneumonia (6%)  Acute Encephalitis (1 per 1000)  SSPE (1 per 100,000)  Case fatality rate of 1-2 per 1000 Maternal measles associated with an increased risk of premature labour, miscarriage and low-birth weight infants.	Mild local or systemic reaction (14.2%) Aseptic meningitis (1 per 100,000) Encephalitis (1 per million) Anaphylaxis (<1 per million)

Link to Immunisation Handbook (2006) Chapter 9 - Measles

Link to Measles Fact Sheet click here