Measles

In 2017, Aotearoa New Zealand was verified by the World Health Organization as having eliminated endemic measles. It has maintained elimination since then. This means that there has not been sustained transmission of measles for longer than a year in New Zealand since 2014. However, measles is often imported into New Zealand following international travel.

New Zealand has continued to experience outbreaks of measles in recent decades. In the 2019 outbreak, more than 2000 people were infected with measles. The majority of cases were in Auckland and Canterbury, and the virus spread across many other parts of New Zealand and into neighbouring Pacific countries. More recently, New Zealand experienced more contained outbreaks in February and May 2023, with both located in Auckland.

Reoccurring measles outbreaks are due to historically low immunisation rates and therefore insufficient levels of immunity across the population to prevent community transmission. Prevention of measles outbreaks relies on improving coverage with measles-mumps-rubella (MMR) vaccination.

More detailed epidemiological information is available on the Institute of Environmental Science and Research (ESR) surveillance website.

An illness characterised by all of the following:

1. cough and/or coryza and/or conjunctivitis and/or Koplik’s spots present at the time of rash onset
2. fever (at least 38ºC if measured) present at the time of rash onset
3. generalised maculopapular rash, starting on the head and neck then spreading down and out and fading.

Nucleic acid amplification tests (NAAT), eg, PCR, are preferred for diagnosis. Nasopharyngeal or oropharyngeal samples have the highest yield particularly in the seven days after the onset of rash. Urine testing can be useful for those presenting more than three weeks after onset of rash. Submitting both a throat or nasopharyngeal swab and a urine sample provides the best yield if sampling is delayed. 

Definitive laboratory evidence for a confirmed case is:

• A positive NAAT of a non-vaccine strain

Suggestive laboratory evidence is: 

• IgG seroconversion between paired sera tested in parallel  
• IgM detection in an unvaccinated person  

The use of serology in the investigation of a suspected measles case is only recommended in cases where NAAT is not possible AND if requested by a medical officer of health after discussion with a clinical microbiologist. Any positive IgM result should be discussed with a clinical microbiologist.

Genotyping information is useful for epidemiology and outbreak investigation. Genotyping via sequencing can be performed on measles-positive NAAT samples at the National Measles and Rubella Reference Laboratory (NMRL) at Canterbury Health Laboratories (CHL), Christchurch. Genotyping should be performed on all:

• New importations
• Index cases and the first 5-10 cases of an outbreak/cluster. If outbreaks continue, then additional samples should be genotyped on a monthly basis
• Sporadic cases that are not epidemiologically linked to other genotyped cases or clusters, and
• All samples requested by the medical officer of health investigating the outbreak.

Samples from patients with recent measles vaccination history can also be tested for the presence of the measles vaccine strain at CHL, SCL Dunedin and LabPlus in Auckland via a vaccine-strain-specific PCR assay.

All requests for NAAT for measles and samples referred for genotyping or testing for the presence of the measles vaccine strain should have recent vaccination status included on the request form.

Sample requirements:

• For genotyping via sequencing and vaccine-strain-specific PCR a minimum of 1 mL of primary patient sample (ideally nasopharyngeal swab sample in universal transport medium) should be sent to the respective laboratory
• In addition, 1 mL of all positive samples should be sent to the NMRL at CHL if possible
• If this is not possible during an outbreak, with high sample numbers, then at least 10 positive samples per week (and all those samples that require genotyping) should be forwarded to the NMRL at CHL.

Note: laboratory testing is not always required for contacts of known cases to be classified as confirmed cases. 

Serology is most useful for detecting IgG in those who have an unclear vaccination history, although commercial assays do not detect all vaccine-induced immunity. There are limited circumstances where IgG testing may be appropriate to test exposed contacts to determine if they are immune, such as: 

• Immunocompromised people or pregnant women for whom normal human immunoglobulin (NHIG) may be recommended if they are known to be susceptible
• Healthcare workers for whom it is too late for post-exposure prophylaxis to be effective. 
• People who need to be excluded from critical duties unless they have demonstrable immunity to measles
• Seeking confirmation of immune status due to unknown vaccination status or partially vaccinated individuals (to support decisions regarding restriction requirements or necessity for a booster vaccination). 

IgM serology is often unreliable, particularly in previously vaccinated people. Recent vaccination may result in an IgM response, and previously vaccinated but infected persons may not develop an IgM response. IgM serology confirmed by the reference laboratory may occasionally help in late presentations and should be interpreted in discussion with a clinical microbiologist.  

After measles vaccination, measles IgM is produced as part of the seroconversion and can be detected for 1–2 months. Serologically diagnosed cases who have received a measles-containing vaccine 8 days to 6 weeks before testing should not be classified as confirmed measles cases unless they are also linked epidemiologically to another confirmed case before vaccination.  

Measles IgG detected without IgM within 1–2 days of a rash strongly suggests prior immunity and that the rash is more likely due to causes other than measles. 

• Under investigation: A case that has been notified, but information is not yet available to classify it as probable or confirmed.
• Probable: A clinically compatible illness where there is a high index of suspicion* of disease, and either laboratory suggestive evidence** or laboratory confirmatory testing is inconclusive or cannot be performed.
• Confirmed: A clinically compatible illness that is laboratory confirmed or epidemiologically linked to a confirmed case.
• Not a case: A case that has been investigated and subsequently found not to meet the case definition.

* A high index of suspicion is if someone has a clinically compatible illness, is susceptible to measles (not immune/immunised) and has been in an area with known measles cases (either in Aotearoa New Zealand or overseas) during the incubation period OR when there is an epidemiological link to a probable case.

** See ‘Laboratory test for diagnosis’ above

About 10 days, but may be 7–18 days, from exposure to onset of fever, and about 14 days, but may be 7–21 days, from exposure to the onset of rash. The incubation period may be longer in those given immunoglobulin after exposure.

Airborne spread or by direct contact with nasal or throat secretions of cases. The measles virus has a short survival time (less than 2 hours) and is rapidly inactivated by heat, sunlight and pH extremes. Both ventilation and masking are effective at reducing (but not necessarily preventing) transmission of airborne diseases.

For public health purposes, the case is considered infectious from 4 days before appearance of rash to 4 full days after onset of rash (counting the day of rash onset as day 0), ie, this is a total of 9 days.

Attending health practitioners or laboratories must immediately notify the local medical officer of health of suspected cases. Notification from health practitioners should not await confirmation.

Wherever possible, all relevant clinical and demographic information on the suspected case should be collected within one day.

Obtain a history of vaccination, immunodeficiency, contact with a probable or confirmed case and travel.

In consultation with the attending health practitioner, obtain laboratory confirmation where possible and necessary. Testing may not be necessary or appropriate for cases with an epidemiological link to a confirmed case in outbreak situations.

Isolate (ie, stay home unless seeking health care) for at least four days after the appearance of the rash. If seeking health care call ahead to inform that they are infectious with measles.

In health care facilities, airborne precautions should be taken until four days after the appearance of the rash.

Vitamin A treatment can reduce the risk of fatality and eye complications and should be considered particularly in cases of hospitalised children, and in cases with severe or complicated measles, immunodeficiency, malabsorption, malnutrition or documented vitamin A deficiency.

Advise the case and their caregivers of the nature of the infection and its mode of transmission. If other vaccinations are incomplete, recommend the case catches up once they are through the acute illness.

Public health services should alert doctors and laboratories in areas where the case may have acquired the infection or was infectious and should ask these doctors and laboratories to notify all cases to the public health service promptly. Part of the reason for this is that early prophylaxis given to susceptible contacts (see below) can reduce the risk of developing disease. Consider a media alert to assist in finding cases.

Close contact

Any person who has had direct contact with a case or has been in a confined space with an infectious case or has spent time in that space within one hour after it has been vacated by the case.

Confined settings may include early childhood services, classrooms, households, transportation, waiting rooms, consultations rooms, indoor occupational or social settings. Discretionary judgement may be required by the local medical officer of health, noting that measles is highly infectious, and this should be taken into account when determining contacts and public health action. However, if appropriate control measures (eg, mask wearing, ventilation, and other infection prevention and control measures) have been in place, a medical officer of health may use their discretion in determining whether a person is a close or casual contact.

Casual contact

Any person who has attended an event in an indoor setting where at least some (but not all) of  the individuals who attended are likely to have had sufficient contact with the infectious measles case to put them at risk of infection.

This contact category can be used where either those who attended are unknown, or their level of exposure to the infectious case cannot be determined. For example, individuals who went to the same café as an infectious case but the timing of visits and proximity of patrons to the case cannot be determined.

Acceptable presumptive evidence of immunity

• Date of birth before 1 January 1969* (they are presumed to be immune following exposure to the wild virus).
• Documentation of vaccination:
  • For children aged 12 months to under 15 months: documentation of at least one dose of measles-containing vaccine after their first birthday.
  • For individuals aged 15 months and older: documentation of two doses of measles-containing vaccine, given at least one month apart and given after their first birthday. This can include the contact’s second measles-containing vaccine after exposure to an infectious case as long as it has been given within 72 hours of initial exposure.
• Documentation to confirm immunity, eg, serology.
• Documentation of previous infection, eg medical records.

*Measles vaccine was introduced into New Zealand in 1969.

Advise all contacts to seek early medical attention if symptoms develop and take precautions so as not to infect others. It is important they telephone and alert the health provider before attending their medical centre to prevent the risk of spreading the virus in health care settings.

Susceptible contacts quarantine (ie, stay home unless seeking health care) from seven days after first exposure to an infectious case until 14 full days after last exposure to an infectious case. That is, if there has been a single exposure, quarantine is for seven days (from 7 until 14 days after exposure). However, if exposure has been for more than one day (potentially exposure to several cases with differing infectious periods), then quarantine will be for more than seven days.

However, partially vaccinated contacts (those with only one documented dose of MMR):

• Will not be requested  to quarantine, but
• Should be excluded from higher risk settings*, unless the setting is one where all others present have acceptable presumptive evidence of immunity, and
• The contact will continue to be monitored for signs and symptoms consistent with measles for at least 14 days, and
• A second MMR needs to be administered as soon as possible (but at least four weeks from the first dose).

* Higher risk settings include early childhood education centres, healthcare, and other settings where there may be high levels of contact and with susceptible people who may be more prone to developing severe disease if infected.

The medical officer of health should consider whether it is necessary to exclude children who are contacts from early childhood services using the Education (Early Childhood Centres) Regulations 1998.

Further information on post exposure MMR vaccination and quarantine/exclusion, including an algorithm, is available at Post-exposure MMR vaccination and exclusion.

Non-susceptible contacts (see ‘Acceptable presumptive evidence of immunity’ above) need no restriction.

For susceptible close contacts, consider the use of MMR vaccine, human normal immunoglobulin (HNIG) or intravenous immunoglobulin (IVIG). The below information has been taken from the Immunisation Handbook and provides advice for human normal immunoglobulin prophylaxis for measles contacts.

Human normal immunoglobulin (HNIG; Normal Immunoglobulin-VF) is recommended for measles-susceptible individuals in whom the vaccine is contraindicated and susceptible pregnant close contacts. For these individuals, HNIG 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.

HNIG provides no benefit to those who are already exhibiting symptoms of measles.

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

• immunocompromised or immune-deficient people
• susceptible pregnant women (if no evidence of two measles-containing vaccine doses, give HNIG or check serology)
• immune-competent infants aged under 6 months: because maternal antibody wanes in the first six months of life, evidence of maternal vaccination status or serology tests may not predict protection for these infants. Maternal serology may be helpful for neonates. The role of an infant measles IgG test is unclear but may be helpful if available rapidly. Discuss use of HNIG for these infants with a paediatrician
• immune-competent children aged between 6 and 12 months, who are outside the 72-hour exposure window for MMR vaccination
• infants born prematurely <28 weeks’ gestation are considered non-immune irrespective of maternal immune status
• infants aged under 12 months born to mothers who received immunomodulatory biologic agents in pregnancy, unable to receive MMR0.

For further details for infants under 6 months and immunocompromised children refer to the Starship Child Health guidelines.

The recommended dose for pregnant women and immunocompromised or immunodeficient people is 0.6 mL/kg intramuscularly, to a maximum dose of 15 mL, usually administered as three 5 mL injections.

Appendix 6 of the Immunisation Handbook outlines considerations around passive immunisation with immunoglobulin. There is some evidence that a dose of MMR vaccine, when given to an unvaccinated or partially vaccinated person within 72 hours of first contact with an infectious case, may reduce the risk of developing disease.

If there is doubt about a contact’s immunity, give MMR vaccination as there are no undue effects from vaccinating an individual who is already immune.

Stress the importance of two doses of measles vaccination for all children and encourage early childhood services to keep up-to-date immunisation records for all attending children.

Two doses of MMR vaccine are recommended for all children (without contraindications): the first at 12 months of age and the second at 15 months of age. Where dose/s have been delayed or missed, catch-up vaccination is recommended.

Catch-up vaccination is recommended for anyone born from 1 January 1969 who has missed doses of measles vaccine (or who cannot show they are immune).

New Zealand residents are eligible for a free primary course (two doses of MMR vaccine).

Depending on circumstances, such as during an outbreak or prior to international travel, a second MMR dose may be given 1 month after the first dose. During a generalised community outbreak, an extra dose (dose 0) may be offered to infants 6–12 months of age, but as effectiveness cannot be guaranteed, all children still need two further doses when they are over 12 months of age. This is because the seroconversion rate is lower when MMR is administered to an infant under 12 months of age.

Ensure that the attending health practitioner and laboratory collection rooms understand the importance of prompt isolation of a suspected case within their health care facility and the need to leave the consultation/examination room vacant for at least 1 hour after the suspected case has left it. Visits of cases and contacts (who may be entering the infectious period) to laboratory collection rooms should be planned ahead by telephone.

Ventilation and masking are effective at reducing transmission of airborne diseases.

Ensure complete case information is entered into NDMS (Notifiable Disease Management System).

If an outbreak occurs, contact 0800GETMOH - CD option, and outbreak liaison staff at ESR, and complete the Outbreak Report Form.

• Communicable Diseases Prevention and Control Unit. 2011. Measles. In The Blue Book: Guidelines for the control of infectious diseases (pp 127–130). Victoria: Public Health Branch, Department of Human Services, State Government of Victoria.
• Department of Health, Australia. 2019. Measles: CDNA National Guidelines for Public Health Units. Canberra: Department of Health.
• Gastanaduy PA, Redd SB, Clemmons NS, et al. 2019. Chapter 7: Measles. In Manual for the Surveillance of Vaccine-Preventable Diseases. 7.1–7.21. Atlanta: Centers for Disease Control and Prevention.
• Heymann D (ed). 2014. Control of Communicable Diseases Manual (20th edition). Washington: American Public Health Association.
• Hope K, Boyd R, Conaty S, et al. 2012. Measles transmission in health care waiting rooms: implications for public health response. Western Pacific Surveillance and Response 3(4) 33–38.
• Ministry of Health. 2020. Measles. In Immunisation Handbook. Wellington: Ministry of Health.
• Public Health England. 2019. National Measles Guidelines. London: Public Health England.
• Public Health Laboratory Network. 2009. Measles Laboratory Case Definition. Canberra: Department of Health and Ageing, Australian Government.
• WHO. 2009. Measles vaccines: WHO position paper. Weekly Epidemiological Record 84 (35): 349-360.
• WHO. 2005. Field guidelines for measles elimination. Manila: WHO Regional Office for the Western Pacific.