health & science

Why we don’t have enough measles vaccines

With global cases of measles skyrocketing last year, did New Zealand do enough to prepare for a potential measles outbreak?

There are at least 1443 confirmed cases of measles in New Zealand so far this year. It’s the worst outbreak in over two decades and it’s not likely to be over soon.

According to Immunisation Advisory Centre director Dr Nikki Turner, the outbreak was "not unexpected" and there’s only one thing which will end it.

“It's completely dependent on vaccinating people who currently are spreading the virus because they're under- or unvaccinated. The more we can vaccinate to stop the spread of each virus, the more we can stop these multiple outbreaks.”

There’s just one problem. Vaccines are being rationed, with children under five getting priority because there aren't enough vaccines in the country to go around. Even additional doses on order might not be enough to plug all the gaps and attain herd immunity. 

This year's outbreak dwarfs previous years. Data Source: ESR

Historical data drives ordering

The forecast of vaccine demand has fallen very short of demand.

A Pharmac spokesperson told Newsroom normally 12,500 doses were distributed each month in New Zealand. 

“We forecast how many doses will be needed based on historical data, which includes higher demand during outbreaks ... This means that we distribute around 9500 doses per month to general practices for those babies, and a further 3000 (approximately) per month for other population groups, totally around 12,500 per month.”

In August, as the New Zealand outbreak ramped up, the number of doses distributed jumped to 25,690. In September to date, 85,200 doses have been distributed. 

In addition to normal ordering, 170,000 doses are set to arrive in “the next few months”.

Currently, GPs are told to vaccinate children aged five and under. Others are being being turned away and told to wait, unless a doctor strongly believes they should be vaccinated. 

Official data based on monthly data reported to WHO (Geneva) as of March 2019

But is ordering based on historical levels the best approach when there are measles outbreaks around the world?

Last year saw worldwide levels of measles increase. World Health Organisation data puts the total worldwide cases in 2017 at 155,570. By 2018, this had jumped to 403,520. 

It could be argued that last year’s global spike should have been a red flag that an outbreak was likely. Pharmac said disease trends were taken into account:

“Global outbreak trends is one factor taken into consideration for forecasting. International outbreaks may cause isolated imported cases as travellers enter New Zealand."

Even so, the forecast has been woefully short. 

Turner said New Zealand's current outbreak came as no surprise.

“We were predicting that there would be outbreaks of measles in New Zealand and we had been requesting for several years that we needed a national campaign to close the gap. So this is not unexpected.”

She believes a national campaign is urgently needed and understands the Ministry of Health is keen to do it when there is enough vaccine available.

Knowing how many doses are required is a bit like pulling a number out of a hat. However, it’s likely to take more than the additional 170,000 doses on order. Accurate data  from before 2005, when the National Immunisation Register was created, doesn't exist. What little is known is patchy.

Turner believes that in the early 1990s, only 50 to 60 percent of two-year-olds were fully vaccinated.

A 60 percent vaccination rate from 1990 to 1999 would leave around 278,000 people potentially under- or unvaccinated. Add in New Zealand’s roughly 1.2 million 30 to 49-year-olds who may have only had one dose of the vaccine and the number of doses required dwarfs the number currently ordered.

Without the register, there’s no way to know how many people in those groups may have had catch-up shots and be fully immunised. 

20-29 year-olds are not a priority for vaccination unless a GP's 'clinical judgment' decides it's necessary. Data Source: ESR

What would a catch-up campaign look like?

Turner said different countries do catch-up campaigns differently.

"Low-income countries, they go out and they offer a vaccine to every person in the age group at risk, regardless of their vaccine history."

She thinks New Zealand could have a region-by-region approach using records held by GPs.

"You start from the records and you let people know. Then you make it very easy for people to access vaccination, alongside a national campaign to say we can stop measles - this is how we can do it. These are the opportunities for you to get vaccinated."

As of last week 482 people had been admitted to hospital with measles, including 114 babies. 

Read more:

Measles: As certain as death and taxes

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