Background information on measles

Fact sheet
5 June 2005

"It is unacceptable that children should continue to die from measles. We have a safe, cheap, and effective vaccine. We can eliminate measles." -- Dr Shigeru Omi, Regional Director for the WHO Western Pacific Region

What is measles?

  • Measles is caused by a virus (Paromyxovirus family).
  • Symptoms usually start 10-12 days after infection.
  • The initial symptoms are fever, cough, conjunctivitis, and runny nose.
  • The characteristic rash (raised red blotches) usually appears 14 days after infection; it spreads from the head to the trunk and then the limbs over 3 to 4 days.
  • After recovery there is life-long immunity.

Complications of measles

  • The risk of developing complications varies, being much higher in developing countries, especially in under-nourished cases.
  • Mortality rates can be as high as 2-15% in developing countries.
  • About 1 in every 5-10 cases develops ear infections (otitis media), diarrhoea, or pneumonia.
  • About 1 per 1000 cases gets brain inflammation (encephalitis). Those cases that do not die are often left with permanent brain damage.

Spread of measles

  • Measles only affects humans.
  • It is one of the most infectious viruses.
  • Spread is from person-to-person by direct contact or through airborne spread.
  • Before immunization began in 1963, about 99% of children would get measles in childhood.
  • On average, one case infects 15-20 other cases in a population with no immunity.

Measles vaccine

  • Available since 1963.
  • Live virus vaccine: attenuated (weakened) form of the natural (‘wild’) measles virus.
  • Infection with the vaccine virus generates life-long immunity without causing the illness or complications of natural measles.

Measles vaccine efficacy

  • A single dose of vaccine, given in ideal conditions, protects about 85% of children if given at the age of 9 months; about 90% at the age of 12 months.
  • Vaccine efficacy is reduced if the vaccine is damaged by heat or light.
  • A second dose of vaccine is recommended for all children to protect those who were not protected by the first.
  • Two doses will protect about 99%.

Measles vaccine safety

  • Causes a mild measles-like illness (rash and fever) in about 5%
  • More serious reactions are rare and do not usually cause long-term problems.
  • May cause encephalitis in less than 1 per million doses – not certain.

Current status of measles control in the Western Pacific Region

  • Every country in the world uses measles vaccine in their immunization programme.
  • Cambodia was the last country in the Region to add measles vaccine to its programme – in 1986.
  • Measles control continues to improve with more countries and areas achieving very low levels of measles circulation; some have already achieved elimination.
  • Measles remains relatively common in several countries:
    • Cambodia
    • China
    • Japan
    • Lao People's Democratic Republic
    • Papua New Guinea
    • Philippines

Burden of measles in the Western Pacific Region

  • Measles cases and deaths are under-reported, especially in the areas with the highest burden. Therefore, data on measles that is only based on reported cases is unreliable.
  • A 2003 estimate was of about 30 000 deaths and one million cases per year in the Region; whereas only about 100,000 cases were reported (deaths were not reported).

Measles elimination

  • Elimination does not mean zero cases – because importations and some spread from these are inevitable.
  • Elimination means that measles virus is no longer circulating and that following any importation any further spread is very limited.
  • This means that once elimination is achieved, it must be maintained by keeping practically every person immune to measles.
  • Measles has already been eliminated from a significant number of countries.

Measles elimination strategy

  • Ensure that 95% of children get two doses of measles vaccine.
  • Improve surveillance to detect all suspected cases of measles.
  • Provide laboratory support so that laboratory testing is available to confirm diagnosis.

Achieving measles elimination requires:

  • Political commitment
  • Financial commitment
  • Technical capacity

Measles elimination, child survival, and health systems

  • Most measles deaths in the Region occur in disadvantaged populations where regular health services are not available for various reasons, such as cultural and geographical barriers.
  • The high coverage requirement for measles elimination, and the need to achieve that high coverage routinely for every birth cohort is challenging.
  • Addressing that challenge, and providing regular immunization services for the disadvantaged population can provide the foundation for delivering other life-saving interventions and building regular health services.
  • As well as the indirect benefits, measles elimination will be of greatest benefit to disadvantaged populations as they are the ones that have the greatest disease burden. Measles elimination is an issue of justice and fairness.