Contents

11 Measles

11.8 Public health measures

It is a legal requirement that all cases of measles be notified immediately on suspicion to the local medical officer of health – do not wait for a laboratory confirmation.

11.8.1 Diagnosis

A single case of measles should be considered an outbreak and result in a suitable outbreak response. Although practitioners should have a low index of suspicion for notification, it is important that all suspected clinical cases be laboratory confirmed or epidemiologically linked to a confirmed case.

The standard clinical case definition for measles is ‘an illness characterised by all of the following: generalised maculopapular rash, starting on the head and neck; fever (at least 38oC if measured) present at the time of rash onset; cough or coryza or conjunctivitis or Koplik’s spots present at the time of rash onset’.

It is important that the diagnosis be laboratory confirmed as many viral infections can mimic measles but do not wait for laboratory confirmation before notifying the local medical officer of health. Notify immediately on suspicion of measles. In the first instance, blood should be taken for serological confirmation and a nasopharyngeal and throat swab taken for viral identification by PCR. For instructions on measles specimen collection and transport, see the National Measles Laboratory website (www.measles.co.nz).

Further specimens for viral culture, detection of measles virus by PCR or further serological tests should be taken in consultation with the laboratory. The timing and choice of samples in relation to the onset of symptoms is important. For further information, contact the local medical officer of health or infectious diseases physician. More detailed information is available from the National Measles Laboratory.

11.8.2 ProphylaxisTop

Management of contacts of a measles case should be discussed with the local medical officer of health.

MMR vaccine

There is some evidence that a single dose of MMR vaccine when given to an unvaccinated person within 72 hours of first contact with an infectious person may reduce the risk of developing disease.1 If there is doubt about vaccination status, MMR should still be given. MMR will not exacerbate the symptoms of measles if already incubating the disease but in these situations, any measles-like illness occurring shortly after vaccination is likely to be due to infection.

If MMR vaccine is not given within 72 hours of first exposure, it should still be offered at any interval in order to offer protection from future exposures, unless the vaccine is contraindicated.

In an outbreak affecting infants, the use of MMR vaccine for infants aged 6–14 months should be considered. If MMR vaccine is given to an infant aged under 12 months, two more doses are still required after age 12 months and at least four weeks apart. This is because the seroconversion rate is lower when MMR is administered to an infant aged under 12 months. In an outbreak affecting young children, the second MMR vaccine does not have to be delayed until 4 years of age but can be given at any time from four weeks after the first dose.

Normal immunoglobulin (IG) prophylaxis for contacts

Normal immunoglobulin is recommended for measles-susceptible individuals in whom the vaccine is contraindicated (see section 11.6) and susceptible pregnant contacts. For these individuals, IG is given to attenuate disease and should be given as soon as possible, up to a maximum of six days after exposure. All other susceptible contacts should be offered MMR as post-exposure prophylaxis (as described above). Infants aged under 6 months where there is evidence of maternal immunity do not require any prophylaxis, but will still need the scheduled MMR doses at ages 15 months and 4 years.

Normal immunoglobulin may be recommended for the following contacts of measles cases as soon as possible and up to six days after exposure:

  • immunocompromised or immune-deficient people
  • susceptible pregnant women
  • immune-competent infants aged under 6 months where there is no evidence of maternal immunity (presence of maternal antibody, or documentation of two MMR doses or previous history of measles infection)
  • immune-competent children aged between 6 and 15 months, who are outside the 72-hour exposure window for MMR vaccine.

The recommended doses of IG are:

  • immune-competent infants aged under 15 months should receive 0.6 mL/kg intramuscularly, to a maximum volume of 5 mL
  • pregnant women and immunocompromised or immune-deficient people should receive 0.6 mL/kg intramuscularly, to a maximum dose of 15 mL, recommended as three 5 mL injections.

Prophylaxis with intravenous immunoglobulin

Intravenous immunoglobulin (Intragam P) can be considered for immunosuppressed and immune-deficient measles contacts (who may, for example, have a central venous catheter), individuals with reduced muscle bulk, or in those people for whom large doses are required (see section 1.5 for more information about passive immunisation).

The recommended dose of intravenous immunoglobulin is 0.15 g/kg. See the guidance from the Health Protection Agency for further information (https://www.gov.uk/government/publications/measles-post-exposure-prophylaxis).

If there are further queries, these can be directed to the New Zealand Blood Service medical team via the DHB blood bank.

11.8.3 ExclusionTop

Exclusion of measles cases or contacts should be discussed with the local medical officer of health.

Parents/guardians should be advised that children who are suspected or confirmed measles cases should be excluded from early childhood services, school or community gatherings until at least five days after the appearance of the rash.

Immune contacts (ie, children aged 12 months to under 4 years who have received one dose of measles-containing vaccine after their first birthday and children aged 4 years and older who have received two doses) need not be excluded from these settings. Non-immune (susceptible) contacts should be excluded because of the risk of developing the disease themselves, and the risk of passing on the disease during the prodromal phase to other susceptible children. Advise susceptible contacts to avoid attending school, early childhood services or community gatherings, and to avoid contact with other susceptible individuals, until 14 days after the last exposure to the infectious case.

Given that post-exposure MMR vaccination cannot guarantee protection, susceptible contacts who have received their first MMR vaccination within the 72-hour period after first exposure should also be excluded for 14 days after the last exposure to the infectious case (unless they subsequently meet the criteria for immunity).

Individuals who have received IG prophylaxis should also be excluded for 14 days after the last exposure to the infectious case.

Acceptable presumptive evidence of immunity is:
  • anyone born before 1 January 1969
  • documentation of immunity or previous infection
  • children aged 12 months to under 4 years who have documentation of at least one dose of measles-containing vaccine after their first birthday
  • individuals aged 4 years and older who have documentation of two doses of measles-containing vaccine, given at least one month apart and given after 12 months of age.

For more details on control measures, refer to the Measles chapter of the Communicable Disease Control Manual 2012.48