New Zealand is in the thick of its worst measles epidemic in 22 years, with more than 850 cases so far. As one vaccinologist says, it was predictable, entirely preventable and the government were warned. So how did we get here? Jamie Morton and Natalie Akoorie explain.
Where did this outbreak come from?
Whittling this year's measles catastrophe down to a single origin is impossible, for the simple reason that there really isn't one. It's a messy story.
The first outbreak of measles in New Zealand this year began in the Waikato in January with 10 cases.
That strain came from Malaysia but authorities don't know where the first person picked up the virus, according to data released by the Institute of Environmental Science and Research [ESR].
That same month another outbreak was reported by the Bay of Plenty District Health Board and spread to the Waikato, with three confirmed cases contained by February.
ESR data shows the virus in that outbreak was contracted in Japan.
Again in February a third outbreak of a strain circulating in the Philippines, developed in Canterbury and spread to Southern Canterbury and Waitematā in Auckland, affecting 40 people and taking a month to bring under control.
It was a strain that had never been seen before in New Zealand.
The North Island was then hit by six more outbreaks between March and June.
Outbreaks four, six and nine are "ongoing", meaning health authorities have not been able to contain them.
Two of them started in Auckland and Waitematā, and one in the Lakes DHB catchment, with a total of 12 other DHB regions affected by the three outbreaks.
The data shows the virus is also coming from countries such as Thailand, Australia, Singapore, Afghanistan, the United Kingdom, China and Vietnam.
Alongside the nine outbreaks that have infected almost 900 people across the country, there have been seven single cases where only one person was diagnosed.
The outbreaks are the worst in 22 years and have sparked a national response by the Government, including setting up drop-in vaccination clinics in South Auckland, where more than 500 cases of the virus have been notified.
In two of the smaller outbreaks where only three people were infected one was a family, and the others members of the public in a doctor's waiting room.
ESR public health physician in the Health Intelligence Group, Dr Jill Sherwood, said in those small outbreaks they were contained because people either quarantined themselves quickly or they only came into contact with people who were immune.
The data showed all three different measles strains currently in the country were contracted overseas, either by Kiwis returning home or by visitors to New Zealand.
Sherwood said New Zealanders were not taking the global measles outbreaks seriously enough and warned anybody travelling internationally to check their immunity status first.
"International airports are bad places to be. The problem is we will get ongoing importations because there is so much measles around in the world."
What's the bigger picture, here?
Shots have been fired at the anti-vaccination crowd – but experts say they aren't solely to blame.
Rather, Auckland University vaccinologist Helen Petousis-Harris put the spate down to several reasons.
Firstly, there had been historically poor uptake of the MMR vaccine, mainly affecting people in their teens through to around 30 years of age.
When measles vaccines were introduced, the incidence of the disease declined, meaning that fewer people caught measles so never became immune.
In more recent times, New Zealand improved its previously dismal vaccine uptake, partly thanks to hard work by health workers and a national electronic register.
But Petousis-Harris said we were still falling short of the national target for the MMR vaccine – that's 95 per cent of all infants to be fully immunised by age 2.
While we nearly got there in 2014, the rate has dropped to 91 per cent – and to 86 per cent among Māori.
"This means there are too many toddlers and young children susceptible and, of particular concern, the unimmunised people are not evenly dispersed among the rest of the population, creating hot-spots for diseases like measles."
Meanwhile, measles has been making a comeback across the globe – a direct result of anti-vaccination activities and a consequent rise in "vaccine hesitancy".
"In fact, the World Health Organization declared this problem as one of the 10 greatest threats to public health for 2019 - pretty sobering," she said.
"This means immunisation rates are plummeting and more people are susceptible to contracting and transmitting measles.
"It also means there are more people walking off planes and into our communities carrying the measles virus, so we are being challenged with the virus more often."
Thanks to social media, the anti-vaccine lobby had become coordinated, funded and lawyered up.
This has resulted in "an explosion" of fake academia – or bad science funded by anti-vaccine lobby groups – along with legal cases and the spread of this fake news that she described as an "insidious vermin hell bent on the destruction of public health".
"Welcome back to the dark ages."
How does this stack up with previous outbreaks?
"This is the largest outbreak since the 1990s - by a lot," Petousis-Harris said.
Back in 1991, health authorities were inundated with thousands of cases – seven deaths among them – and then managed to stave off another outbreak in 1997 with a mass-vaccination campaign.
After the introduction of the measles vaccine in 1969, measles continued to occur every year until 1980, with a pattern of "low years" – that's an average of approximately 100 hospitalisations per year - alternating with "high" or "epidemic" years, or an average of 300 hospitalisations per year.
This was because vaccination rates were not high enough to prevent outbreaks.
Experts say increased uptake of the measles vaccine, which is thought to have reached 70 per cent or more by 1980, resulted in this epidemic cycle becoming more accentuated, with fewer cases and longer periods between epidemics.
Measles virtually disappeared between the epidemic years, which began to occur less frequently – 1984/85, 1991 and 1997.
There were 400 hospitalisations in the 1984/85 outbreak and a total of 943 hospitalisations in the 1991 and 1997 epidemics, with no deaths reported in the latter.
If there was any positive to draw from this episode, it's that more people have been coming forward to get an MMR shot – which will hopefully get New Zealand closer to its 95 per cent target.
So how does the MMR vaccine actually work – and what's herd immunity?
The MMR vaccine works by stimulating the body to make protective immunity against the three viruses; measles, mumps and rubella.
It's a live vaccine, made using the mumps, measles and rubella viruses that have been weakened, or attenuated.
After vaccination, the weakened vaccine viruses replicate or grow inside the body, which is why only a very small dose of virus is given to activate the immune system.
One dose of MMR vaccine protects 92 out of 100 people and two doses protects about 98 out 100 people against measles.
This protection is likely to be lifelong, or near lifelong. Measles has been eliminated in population achieving high levels of vaccine coverage.
The vaccine itself has come in a few forms over recent decades.
A single dose of the one introduced in 1969, for children from 10 months to five years, offers 95 per cent immunity and two doses provide 99 per cent immunity.
In 1974, the one-dose vaccination was moved to 12 months of age, and by 1981, one dose was given at 12 to 15 months.
In 1991, amid the last big epidemic, a second dose was introduced for children up to 11 years of age, and at the start of the smaller 1997 epidemic, children aged 10 were targeted for a second dose.
Anybody aged from 38 to 50 without documentation to prove a second dose is eligible for a free measles vaccination.
Before a vaccine became available, everyone would have measles – something of a right of passage of childhood - but most would recover and become immune for the rest of their lives.
Epidemics used to happen every few years, and as people were born, the number of susceptible people would grow enough to allow the virus to recirculate.
This has been kept down through what's called herd immunity – and we might have just lost it.
As it had long stood, one out of every 100 vaccinated people weren't protected against measles.
Provided there are high levels of vaccination in a community – like 95 out of every 100 - there was a very high probability that the one person out of 100 vaccinated people who did not develop immunity from the vaccine, would be protected by herd immunity.
However, measles is extremely easy to catch and pass on.
In a population not vaccinated at all, someone with measles might infect between 14 and 18 other people.
This could rapidly lead to high levels of disease cases in a community or geographical area.
And if there were high levels of disease in a community, due to lower vaccination levels, it was quite possible that some of those who failed to make an immune response to the MMR vaccine might catch measles too.
What's being – and should be - done?
Last week, Associate Health Minister Julie-Anne Genter vowed that the outbreak would be a "top priority".
The Ministry of Health had now activated a national coordination centre that would work with authorities like Auckland DHBs and the Auckland regional Public Health Service.
"People under the age of 50, especially children, who have not been vaccinated, should seek a free vaccination from their doctor as soon as possible," Genter said.
Meanwhile, there was a risk New Zealand might be stripped of its measles elimination status – officially defined as an "absence of endemic measles virus transmission in a defined geographical area for more than 12 months in the presence of a well-performing surveillance system" – that it was awarded two years ago.
"We could lose it over this outbreak if we do not do something really fast," Petousis-Harris said.
"We would then have to demonstrate no sustained transmission in our population all over again."
She saw the only solution as a targeted mass-vaccination campaign.
It would save money: a cost-benefit analysis of a mass measles immunisation campaign in New Zealand showed that, in 2014, the first 187 confirmed and probable cases cost more than $1 million due to loss of earnings, management of cases and hospitalisation costs.
"Given that the hospitalisation rate during this current 2019 outbreak has been around 30 to 40 per cent, rather than the 10 to 15 per cent seen in previous outbreaks, I shudder to think what the costs have been this far."
It would also save misery – around a third of those patients in the current outbreak had been hospitalised.
Petousis-Harris said that, based on a study from 2017, there were 435,742 susceptible people here, and vaccinating just 104,357 would make a big difference.
"National level authorities have known for years that these immunity gaps are a problem yet have failed to act, leaving the management to local DHBs," she said.
"All the systems and processes required to deliver a targeted mass campaign to those that need it are already in place, they just need resourcing and support."