After prolonged outbreaks in Christchurch and Auckland, measles is taking root in the Pacific.
On Wednesday, Tonga's Ministry of Health declared all government primary schools would be closed until 25 November to further contain the outbreak of measles. Tongan health authorities are also planning on re-vaccinating thousands of people after it was discovered some historical vaccinations might not be effective.
Samoa is the worst affected, with over 600 reported cases so far, and at least three people confirmed dead. This morning, Foreign Minister Winston Peters announced New Zealand is sending 3,000 MMR vaccines and 12 nurses to Samoa to "assist in containing a serious and growing measles outbreak”.
The SMC asked an expert to comment on the outbreaks of measles in the Pacific.
Dr Helen Petousis-Harris, vaccinologist, University of Auckland, comments:
Are there any overall trends in immunisation rates across the Pacific? How do Pacific nations compare to New Zealand's immunisation rates?
"Many of the Pacific Nations have quite good immunisation coverage, comparable to New Zealand. For example, Tonga’s uptake of measles vaccine is about 85 – 99% depending whether you believe WHO-UNICEF or Tongan administrative data. In Fiji, the uptake is 94% reported by WHO-UNICEF and >80% by local administrative data.
"However, this is not the case for Samoa, which has one of the poorest uptakes of measles vaccine in the world, more in line with some of the most devastated countries in Africa. Samoa’s immunisation coverage has trended down for almost 20 years leaving a large proportion of the population susceptible to diseases such as measles. The estimate for 2018 was 31% by WHO-UNICEF, and 40% from local administrative data. Whichever you believe, it is dismal."
Why are there so many deaths in Samoa when there haven't been any in New Zealand so far in this outbreak?
"This is pretty damn sad.
"Samoa are seeing a high number of measles-related deaths, about 1 per 100 notified cases. It is important to note that we cannot compare this to New Zealand’s recent epidemic and perhaps it is useful to consider some differences in health statistics between us.
"First, Samoa is a lower-middle-income setting and do not have health care that is either comparable or as accessible as in New Zealand. Second, children in Samoa are more likely to suffer malnutrition or die in early childhood than children in New Zealand. In Samoa, about 18 per 1,000 children die before 5 years of age whereas in New Zealand this is about 6 per 1,000. The current estimates for measles mortality in settings like Samoa are on average 2 per 100. Another consideration is that the number of cases may be significantly under-reported."
What role has New Zealand played in infectious disease prevention or spread among Pacific nations?
"We know that New Zealand has exported measles to the Pacific Islands. We might predict this will continue while we still have quite a few cases. We might also predict that given the high number of cases in Samoa that the inverse will occur, in fact this has already been reported this week - the disease will be easily imported back. Given we have not yet dealt with our own immunity gaps we cannot get complacent."
Conflict of interest statement: Helen has led a number of industry-funded studies. These have all been investigator conceived and led. She does not receive honorarium from industry personally. She has received industry support to attend some conferences and has contributed to Expert Advisory meetings for GSK, Merck, and Pfizer.