Measles is highly contagious - up to 90 percent of non-immune people will be infected if they are exposed to the virus. Photo: 123RF
Explainer: Confirmation of a measles case in Auckland has put health authorities on high alert in case of another deadly outbreak.
Measles is highly contagious - up to 90 percent of non-immune people (those who have not been vaccinated or have not already had it) will be infected if they are exposed to the virus.
The measles vaccine is free, delivered as part of the MMR vaccine (measles, mumps and rubella).
About 80 percent of New Zealanders are immune - well below the 95 percent coverage needed to prevent an outbreak - and it is lower still for young children, who are among those most at risk of serious complications.
Just 76.4 percent of two-year-olds were fully vaccinated as of December last year. The rates were worse for Māori babies (63.3 percent) and Pacific (70.4 percent).
This Q&A explainer lays out the facts.
What is measles?
Measles is one of the most infectious diseases known, infecting children as well as adults via coughing, sneezing or talking. It is not known to affect any other species.
People who come into contact with the disease who are not immune through vaccination or previous infection are about 90 percent likely to become infected.
Before vaccines, 90 percent of people over 20 had been infected at some point in their lives.
About one in 10 people who contract measles need hospital treatment. The virus can live in the air for hours after a person has been coughing and sneezing in the area.
Read Health NZ's advice on measles.
Symptoms include fever, coughing, having a runny nose and watery 'pink' eyes, and sometimes small white spots on the back inner cheek. They start between seven and 18 days after exposure.
Another three to seven days later, usually about 14 days, a blotchy rash which can last up to a week tends to start on the face and head before spreading down the body.
Symptoms can last for about two weeks in total.
People with the disease are infectious about five days before and after the rash appears.
The basics
Measles is spread by contact with respiratory secretions through coughing and sneezing.
Infected persons should stay in isolation - staying home from school or work.
The best protection from measles is to have two MMR vaccinations. MMR is available from your family practice and is free to eligible persons.
People are considered immune if they have received two doses of MMR vaccine, have had a measles illness previously or were born before 1969.
Anyone believing they have been exposed to measles or exhibiting symptoms should not go to the ED or after hours' clinic or general practitioner - instead they should in the first instance call their GP.
Measles can also lead to complications in up to 30 percent of cases, including ear infections with the potential to cause deafness (7 percent), diarrhoea (6 percent), pneumonia (6 percent), seizures and - in one in 1000 cases - swelling of the brain, which leads to permanent brain damage about a third of the time.
There is also a longer-term risk of subacute sclerosing panencephalitis (SSPE), a progressive, disabling and ultimately deadly brain disorder, which develops seven to 10 years after people contract measles, despite seeming to fully recover.
SSPE is thought to occur in about four to 11 of every 100,000 people who contract measles. The risk may be higher for those who contract it when they are younger than two.
Alerts have been issued after a new measles case was confirmed at the weekend, with people in Auckland asked to check if they could have been exposed. Photo: AFP / Science Photo Library
How deadly is measles?
Measles can kill.
The highly contagious nature of the disease means individuals' overall risk of death from an outbreak is higher than for other diseases simply because they are more likely to contract it.
The US Centers for Disease Control reports death in 0.1 to 0.2 percent (one or two in every thousand people infected) between 1985 and 1992 in the US.
In the last national outbreak in 2019, 35 percent (775/2213) of cases were hospitalised for treatment of complications, and two unborn babies died.
The strain also spread to other countries, including Samoa, where 5707 cases were recorded and 83 people died.
The World Health Organisation (WHO) reports that before the introduction of the measles vaccine in 1963, major epidemics occurred every two or three years, causing an estimated 2.6 million deaths a year.
Pneumonia accounts for 60 percent of measles deaths, while swelling of the brain from measles is 15 percent fatal.
The likelihood of death in people with malnutrition is also comparatively high - about 10 percent - particularly for those with a vitamin A deficiency.
Adults and children aged under five are also more at risk than older children.
Is measles still common?
Measles still occurs throughout the world, but particularly in Africa and Asia where vaccination rates are lower.
It is the world's most common vaccine-preventable cause of death among children.
By the end of 2023, 82 (42 percent) countries had been verified to have achieved or maintained measles elimination, but no region had achieved and sustained elimination, according to the WHO.
Since 2012, all cases in New Zealand have originated overseas.
During the Covid-19 pandemic, estimated global coverage with the first dose of measles-containing vaccine dropped to 81 percent, the lowest level since 2008.
Between 2022 and 2023, estimated measles cases increased 20 percent worldwide, from more than 8.65 million to 10.3 million, while the number of countries with large outbreaks jumped from 36 to 57.
The outbreaks were less deadly however, with estimated deaths dropping 8 percent - 116,800 in 2022 to 107,500 in 2023 - mainly because more cases are happening in developed countries with better health services.
What should I do if I think I have measles?
Because of the risk of contagion, people who have measles should not visit their GP, emergency department or after hours clinic.
Instead they should remain isolated, call their GP or Healthline for free on 0800 611 116 for advice and wait at home. They should not go to school, childhood centres, work, sports events, social activities, shopping malls or use public transport.
There is no specific treatment for measles, but pain relief, drinking plenty of water, avoiding bright light and treating sore eyes by wiping crusted eyelids and lashes using cotton wool and water can help relieve some of the symptoms.
GPs and other health professionals are advised not to wait for confirmation of measles, but to advise the Medical Officer of Health as soon as it is suspected.
If a person with measles has any of these symptoms, their doctor should be contacted:
- trouble breathing
- a stiff neck
- feels drowsy or cannot be woken
- coughing up green or yellow thick mucous
- back pain
- sore ears
- having a fit (seizure)
- not passing urine for 10 hours.
People with measles should remain in isolation until 14 days after symptoms end.
Is the vaccine effective? How common is vaccination?
The MMR vaccine is cheap and hugely effective in preventing measles. Two doses of the vaccine prevent the disease in 95 percent of people aged over one, and 98 percent of people aged over 18 months.
A single dose is still quite effective, providing 90 to 95 percent protection, but some people do not respond to it. A second dose is required to ensure success.
Doses must be at least a month apart.
In New Zealand between 1969 and 1990 it was standard practice for doctors to give just one vaccine. People born during this time should confirm that they have had two MMR vaccines.
The vaccine might not be effective in people who have only been vaccinated within the past two weeks, as they may be already infected.
The vaccine is not a cure, but it can still provide protection if given within 72 hours of exposure to the virus.
Since 2019, two doses of measles, mumps, rubella (MMR) vaccine are scheduled - at 12 and 15 months.
The WHO advises 95 percent immunity coverage to prevent outbreaks, which can afflict the unvaccinated, those with weakened immune systems and a very small minority (about 2 percent) of vaccinated people.
Nurses prepare vaccinations during a nationwide campaign against measles in the Samoan town of Le'auva'a, 2019. Photo: AFP PHOTO / ALLAN STEPHEN / UNICEF
Who can get the vaccine?
In New Zealand, the MMR vaccine - which also prevents mumps and rubella (also known as German measles) - is free to anyone born after 1969.
People born before then are believed to be at lower risk because they were likely exposed as a child.
During an outbreak, additional vaccines can be given for those aged over six months.
Pregnant women should not get immunised. Women are advised to avoid pregnancy within 28 days of receiving the vaccine. Pregnant women who contract measles are at risk of miscarriage, premature labour, and low birth weight. It is fine to get the vaccine if you are breastfeeding.
Babies under 12 months usually do not receive the vaccine, but this limit is reduced to six months during an outbreak.
Those who have experienced a severe allergic reaction (anaphylaxis or hypersensitivity) to a previous dose of any measles vaccine or vaccine components should seek medical advice. Egg allergy does not affect the vaccine.
People who have had a blood transfusion within the past year should seek medical advice.
People who have compromised immune systems from treatments or disease should not receive the vaccine. In particular, chemotherapy erases the body's memory of the virus. People taking medication to suppress their immune system should seek medical advice.
Cancer patients who have finished chemotherapy can be re-immunised after six months for free.
How do I check if I'm vaccinated?
People who are not sure whether they are vaccinated should check their Well Child Tamariki Ora or Plunket book, or contact their GP.
People who cannot find their records are recommended to get another dose. Getting more than the recommended two vaccines is not harmful.
The National Immunisation Register rolled out in 2015 only had MMR added recently, so people are unlikely to find their records there, especially those born before 2005.
Are there risks to getting the vaccine?
Getting the MMR vaccine is considerably safer than the risks from contracting measles.
Within 12 days, up to 15 percent of children who receive the vaccine experience a fever and 5 percent experience a rash. This is mild and not as dangerous as measles.
This fever or rash is not measles, and people who have had the vaccine are not infectious.
About one in 800,000 doses can lead to a (recoverable) inflamed meninges. Acute brain inflammation occurs in about one in a million people, though this is unlikely to be caused by the vaccine.
An allergic reaction is even less likely. However people receiving vaccines, and the guardians of children receiving the vaccine, are asked to stay 15 minutes after it is administered in case anaphylaxis occurs.
This compares to a death rate of one in 1000 people infected by measles, which has a 90 percent chance of infecting those who have not been immunised. The risks of measles are far greater, not to mention the risks of mumps or rubella.
A now debunked study suggested a link between MMR vaccines and autism. The author was found to have falsified his results and scientists have since been unable to find any support for such a link despite hundreds of studies.
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