What is IFNAR1 deficiency?

A recent study into a condition called IFNAR1 deficiency has been published in the Journal of Experimental Medicine.

IFNAR1 deficiency is an extremely rare immune disorder that results in the individual’s immune system not responding to certain viruses. The disorder requires genetic testing to be diagnosed and cannot be prevented. IFNAR1 deficiency was only discovered in 2019.

This genetic condition increases the risk of serious illness and death to the individual when they are exposed to certain viruses, including measles and COVID-19.


IFNAR1 deficiency also increases risk of severe reaction from some vaccines containing weakened live virus such as MMR, yellow fever, and possibly varicella vaccines. Other childhood vaccines and COVID-19 vaccines can be safely given to someone who has IFNAR1 deficiency. 


The study suggests that some Pacific groups (people with Samoan, Tongan and Niuean heritage) could be at more risk of having the rare IFNAR1 deficiency. Initial estimates are that the number of children with two Samoan parents who may be affected by IFNAR1 deficiency is 1 in every 6,450 births. Although we lack equivalent data in Tongan and Niuean populations, we have seen cases where parents are Tongan or Niuean. This may roughly equate to one child per year born in Aotearoa New Zealand, but much more work is needed. For comparison, cystic fibrosis affects about 1 in every 3,500 births. 

Communicating the risks

While the study links IFNAR1 deficiency with MMR vaccination, it is important to note that people with IFNAR1 deficiency are also believed to be at increased risk of severe complications from naturally acquired viral infections including measles, mumps and COVID-19.


Current evidence shows that the public health benefits of vaccination far outweigh the risks of an unvaccinated child becoming seriously ill from a vaccine preventable disease such as measles. Immunisation is vital to protecting the health of New Zealanders and all programmes should continue.

There were more than 2,000 cases of measles in New Zealand during an outbreak in 2019. Since early 2020 there have been no cases of measles, mumps or rubella but this is expected to change now that the border has reopened. New Zealand is particularly vulnerable to a measles outbreak because childhood immunisation rates have been affected by the COVID-19 pandemic. Māori and Pacific communities will be disproportionately vulnerable because of these low vaccination rates.

Measles can be life threatening: around 10% of children with measles will need hospital treatment. Children under 5 years old are particularly at risk from measles and this age group saw the most hospitalisations in 2019. 

Measles can also lead to other complications, including ear infections (which can cause permanent hearing loss), pneumonia, seizures and swelling of the brain – this is rare, but can cause permanent brain damage or death. Mumps can lead to meningitis, cause meningoencephalitis, deafness and orchitis particularly in young people.

During pregnancy, measles can increase the risk of miscarriage, premature labour and low birth-weight babies.


We have over 30 years’ experience in Aotearoa New Zealand and the Pacific with MMR vaccine and years previously with monovalent measles vaccine. There are very few severe adverse events post MMR vaccination recorded in New Zealand.

Health care providers may wish to inform aiga of children with Samoan, Tongan and Niuean heritage of the newly discovered risk as part of obtaining informed consent for the first dose of MMR at 12 months. It is important to also provide information about the risks associated with deciding not to vaccinate against measles, mumps and rubella. We know the risks of not vaccinating, are far greater than the risks of vaccinating. If an older sibling or relative had a severe illness following MMR this should be discussed with immunisation experts.


If a child living in Aotearoa New Zealand has had one dose of MMR and did not develop a serious illness in response, it appears unlikely that they will have a serious reaction to their second MMR vaccine due to undiagnosed IFNAR1 deficiency.

What is being done about it?

The families in New Zealand that have experienced harm as a result of IFNAR1 deficiency are receiving support from specialists.


Since this issue was brought to the Ministry’s attention, we have committed $5.3 million to fund a project to better understand the risks of the IFNAR1 deficiency among Māori and Pacific children in Aotearoa.

The purpose of the Ministry of Health’s investigation is to better understand the clinical and epidemiological risks of the IFNAR1 deficiency among Pacific and Māori children. Māori children are being included in the research as, even though we have not yet recorded a case of IFNAR1 deficiency in the Māori population, they have a common ancestry with many populations in the Pacific. It is important to ascertain whether tamariki Māori may also be affected by this gene.

This project will also investigate whether screening for IFNAR1 deficiency is possible, and if it could lead to early diagnosis and better outcomes for children with IFNAR1 deficiency.

The University of Auckland is leading the project. A governance group has been established to oversee the research with representation from Pacific and Māori clinicians and health experts.

The investigation is expected to take up to five years to complete.