To Avoid A Measles Epidemic, Aotearoa Must Close The ‘Immunity Gap’

The number of children in Aotearoa New Zealand who are not immunised against measles is still growing and we are now close to the tipping point that set off measles epidemics in previous years warn public health experts.

While there have been moves to improve immunisation coverage, the number of measles-susceptible children is still increasing by around 1000 every month. The latest Briefing from the Public Health Communication Centre (PHCC) lays out three actions that are needed urgently to prevent another measles epidemic.

Dr Oz Mansoor and co-authors say most important is a catch-up immunisation for those aged 15 months to 9 years who didn’t get the MMR (measles-mumps-rubella) vaccine. “We can use existing immunisation requirements for primary schools and pre-schools to reach 95% coverage required to stop spread,” says Dr Mansoor. But he says this will need staff to identify the unvaccinated and then engage with parents who may be vaccine hesitant. “It can take time to build a relationship, and to be able to explain the benefits and potential risks of the MMR vaccine with vaccine misinformation so prevalent.”

The measles component of the MMR vaccine will protect for life, with a single dose working for about 90% of children. The second dose protects those where the first dose failed, leading to about 99% protected after two doses.

“In addition to preventing a serious disease that can kill and have other serious consequences, being immunised means that there is no need for quarantine if the child becomes a close contact of a measles cases,” says Dr Mansor

While we address our immunity gaps, the Briefing also urges immediate action to reduce the risk of measles entering the country. “This can be as simple as making sure all travellers are aware of the risk and encouraged to check that they are protected against measles. They should also be urged to take documentation of immunity with them to avoid the need for quarantine if they become a measles contact during their travels,” says Dr Mansor.

The third point of action advised by the Briefing is to have a stronger immunisation component in our response to measles cases. “This could include targeted vaccination of susceptible individuals in communities where cases occur. Basically, looking at a wider ring of immunisations around an outbreak, using the Aotearoa Immunisation Register.”

“The number of susceptible children is now close to that before the 1980, 1985, 1991 and 1997 measles epidemics. Compared to those years, we now have more susceptible young adults, and may be already primed for a large epidemic,” says Dr Mansoor.

NB: In 1996, Dr Mansoor was part of team who predicted the 1997 epidemic based on the number of susceptible children. The planned response was an MMR immunisation campaign, but the epidemic started just before the campaign. The latter is still estimated to have prevented 90-95% of cases, but there were almost 2000 cases and more than 300 hospitalisations.

We are now dangerously close to the threshold again. Presently the number of measles susceptible children increases by 1000 every month. This situation creates a growing ‘immunity gap’ between the number of people immune to measles, and the number of people who need to be immune to prevent epidemic spread.

Parents can have their children immunised at no charge at any GP or healthcare provider, and at many pharmacists. The same applies to adults over the age of 18 years who are eligible for free NZ healthcare.

Dr Mansoor is a Public Health Physician currently on sabbatical with the PHCC.

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