2019 measles outbreak partly blamed on anti-vaccination movement

Canterbury's top medical official says the anti-vaccination movement was partly to blame for last year's measles outbreak in the region.

Thirty-eight people contracted the highly infectious disease between February and April 2019, in an outbreak separate to the one centred on Auckland later that year. 

No one died in the Canterbury outbreak, which is believed to have been sparked by someone arriving from the Philippines carrying the virus. 

Medical Officer of Health Ramon Pink told Newshub that was down to an "across-system response" which leapt into action as soon as the virus was detected.

"The importance of that was the linkages from public health, primary care, laboratories and our planning and funding division and district health board enabled us to jointly respond to this outbreak."

The outbreak is the subject of an article in the latest edition of the New Zealand Medical Journal, published on Friday. In 2017 the World Health Organization conferred elimination status on New Zealand, meaning there is no community transmission of the disease - it simply doesn't exist here, unless it's brought in from overseas.

"Importation of measles is the key way that we do get measles into our community, and that indeed was the case... last year," said Dr Pink.

"With that, we have found that there is still a vulnerability of measles outbreak and the need for a primary care-based measles vaccination campaign nationally to be able to cover those vulnerable groups." 

In addition to the usual vulnerable groups - children too young to get vaccinated and those who can't be immunised for health reasons - Dr Pink says there are many Kiwis aged 15 to 30 at risk. 

"In 1998 a paper was published in a British medical journal linking - purportedly linking - measles to autism. That has been completely debunked, and there have been a number of researchers that have shown quite clearly that is not true. 

"However what that did do was for the generation that were influenced by that paper, they withheld their children from having the measles vaccine. That produced a whole cohort of individuals who are now in the age group of 15-30 who are unimmunised, and therefore there is that vulnerability."

Often thought of as a relatively benign disease, measles can kill. Auckland's outbreak left two unborn children dead, and when the outbreak reached Samoa, 83 people there were killed.

Even if patients survive, measles has the ability to reduce their immunity to other diseases they've already had. 

The 2019 outbreak could have been a lot worse if the region hadn't had a similar outbreak in 2009, which prompted many to rethink their anti-vaccination stance.

"Although we had 38 cases, it could have been a lot worse - we believe the immunisation campaign from a decade previous was able to afford us protection to reduce the number of cases. 

"Those vaccination campaigns do have a profound effect at providing protection for our community to get to that place we call herd immunity, where we can provide the best protection." 

Herd immunity against measles requires at least 95 percent immunisation coverage as it's incredibly infectious. For every person that contracts the virus, on average they'll infect another 12-18 people. Even COVID-19 isn't that easily spread, with an estimated reproduction number of between 2 and 4, provided movement restrictions aren't in place. 

"We already have a national vaccination campaign, and in that we do target our under-fives," said Dr Pink. "However I think there is recognition that we have what we call an immunity gap between 15 years of age and up to the 30s. It's that gap that we really need to target."

The article says New Zealand's current coverage is below 95 percent with " significant pockets of susceptible, non-immune population".

The doctor behind the 1998 paper, Andrew Wakefield, was later stripped of his licence to practise after it emerged he'd falsified data and made fraudulent claims.