MMR vaccination remains a priority

Measles, mumps and rubella in New Zealand

Following the introduction of the combined measles, mumps and rubella (MMR) vaccine in 1990, the number of cases of all three diseases has significantly and progressively declined.¹ Since then, there have been very few large outbreaks and in 2017, the World Health Organization (WHO) verified New Zealand as free of both endemic measles and rubella (see: “Epidemiology definitions”).¹ Historical issues in vaccination coverage, however, have left many adolescents and young adults in New Zealand more likely to have missed full MMR vaccination and at greatest risk of infection (see: “Adolescents and young adults in New Zealand are under-immunised”).^{1, 2} For this reason, the Ministry of Health now recommends that this population group is prioritised for recall for catch-up MMR vaccination to help to close the immunity gap, reducing the risk of future outbreaks.¹

N.B. While adolescents and young adults are currently the priority for catch-up MMR vaccination, anyone born on, or after 1 January, 1969, without documented evidence of immunity to all three diseases may also receive funded catch-up MMR vaccination (see: “Encourage immunisation of susceptible individuals”).¹

Adolescents and young adults in New Zealand are under-immunised

Since the early 1990s, several gaps in MMR coverage have resulted in certain cohorts in New Zealand being under-immunised, particularly adolescents and young adults aged between 15 and 30 years.¹ This gap in immunity is due to a combination of historical issues in vaccination coverage directly affecting this population group, including:¹

• Historically low national immunisation rates, with less than 60% of children being fully vaccinated by age two years in the 1991/92 National Childhood Immunisation Survey.^{5, 6} Coverage increased to 63.1% in 1996 (with lower rates for those of Māori [44.6%] and Pacific [53.1%] ethnicity) and further increased to 77.4% in 2005.^{5, 6} N.B. National immunisation coverage dropped again in the 2010s but increased to 88% (for children aged five years) between 2020 – 2021.⁷
• Unfounded, but widespread vaccine safety concerns regarding a since discredited association between MMR vaccine and the development of autism in children in the late 1990s and early 2000s^* (see: “Vaccination hesitancy” for further information on immunisation concerns)^{8, 9}
• Changes to the timing of the second dose in the MMR vaccination schedule in 2001; from age 11 years to age four years
• Potentially compromised vaccine quality, resulting from inadequate cold chain processes, which have now been rectified
• Vaccine supply shortages, particularly during the 2019 measles outbreak^{10, 11}

^*These claims have been discredited, with over 30 years of epidemiological research confirming there is no evidence of a link between MMR and autism.^{8, 9} The original study (1998) was retracted in 2004 due to dishonest and irresponsible methods, where it was later disclosed to have used incorrect laboratory reports and falsified patient data. For further information, see: www.thelancet.com/journals/lancet/article/PIIS0140-6736(10)60175-4/fulltext.¹

Recent mumps and measles outbreaks highlight immunity gap

The most recent mumps and measles epidemics in New Zealand occurred in 2016/2017 and 2018/2019, with most cases located in the wider Auckland region (see: “Measles, mumps and rubella: an overview”).^{1, 12} Adolescents and young adults aged between 12 – 29 years^* were the population group most affected by the outbreaks (Figure 1).^{1, 12}

During the 2018/2019 measles epidemic, nine outbreaks occurred throughout New Zealand, resulting in 2,213 notified cases, of which:^{1, 13}

• Six outbreak clusters were linked to imported cases; deriving from
  Australia, Thailand, Japan, Singapore and the Philippines

The highest burden of disease was among under-immunised young children, adolescents and young adults; particularly infants aged under two years and adolescents/young adults aged between ten and 30 years^* (see: “Adolescents and young adults in New Zealand are under-immunised”)

^*The age range has been inconsistently reported, i.e. 10 – 15 and 20 – 30 years, and varies depending on data age groupings^{1, 13, 14}

Rubella infection is still rare in New Zealand

The most recent rubella outbreak occurred between 1995 – 1996, mostly involving young adult males, and likely due to the earlier under-immunisation of young males (see: “Vaccination history of measles, mumps and rubella in New Zealand”).¹ Since 1998, no incidences of congenital rubella syndrome (CRS), and very few cases of rubella, have been reported.¹ In 2017, New Zealand was verified by the WHO as rubella-free, and since then only three imported cases of rubella have been reported (Figure 1).¹

Figure 1. Measles, mumps and rubella notifications for adolescents and young adults aged
15 – 29 years in New Zealand from 2013 – 2020.¹²

Measles, mumps and rubella: an overview

Measles

Measles is a highly infectious viral disease caused by a paramyxovirus.¹ It can be transmitted through both airborne spread (coughing, sneezing, breathing) and direct person-to-person contact (via transfer of infectious droplets).^{1, 15, 16} Measles is characterised by clinical features of fever and a distinctive maculopapular rash, and causes an acute immune suppression that leads to widespread infection.^{1, 15} After exposure, the virus has an incubation period of approximately ten days before symptoms appear, typically in three characteristic stages.^{1, 16}

Measles infection increases the risk of further complications such as pneumonia, encephalitis and myocarditis and in rare cases, sub-acute sclerosing panencephalitis^*.¹

^*Sub-acute sclerosing panencephalitis is a rare but serious and fatal degenerative nervous system disease, that arises from persistent, wild-type measles infection and typically appears 7 – 11 years following initial infection¹⁷

Mumps

Mumps is an acute viral infection also caused by a paramyxovirus, and characterised by clinical features of headache, fever and parotitis (parotid salivary gland swelling and tenderness).¹ It is transmitted both indirectly (through airborne droplets) and directly (through contact with urine or saliva), and is most infectious for the period of two days before and five days after onset of parotitis.¹ Widespread mumps infection can lead to further complications such as meningitis, encephalitis, hearing loss, mastitis and oophoritis in females and orchitis in males that can decrease fertility or lead to temporary sterility; it is unknown whether mumps can result in permanent sterility.^{1, 18}

N.B. Parotid gland swelling is most common, but swelling can also occur in other salivary glands and other structures, e.g. the brain and testes.¹

Rubella

Rubella is an infectious disease caused by a togavirus that affects both adults and children.¹ The virus is comparatively less infectious than measles (Table 1), however, maternal infection can lead to serious consequences for the unborn child, particularly if contracted during the first trimester of pregnancy.¹

Congenital rubella syndrome (CRS) is the most severe complication following rubella and results from maternal infection during pregnancy.^{1, 19} CRS is characterised by a number of serious consequences including miscarriage, fetal death and severe congenital defects including hearing impairment, congenital heart disease, cataracts and developmental delay.^{1, 19} Fetal damage can occur in up to 80% of infants if rubella is contracted within the first 12 weeks of pregnancy, decreasing to 50% after 16 weeks and 25% after the end of the second trimester; multiple defects are common.^{1, 19}

Vaccination history of measles, mumps and rubella in New Zealand

The history of measles, mumps and rubella vaccination in New Zealand can provide information to help identify people who are likely to be under-immunised (Table 1).¹

N.B. People vaccinated in other countries may have received monovalent measles or measles-rubella only vaccines, and if applicable, still require immunisation with MMR for full protection.

Table 1. History of measles, mumps and rubella vaccination in New Zealand.¹

^* In 1993, the Department of Health became the Ministry of Health²⁰

N.B. Measles, mumps and rubella are all notifiable diseases and all suspected and confirmed cases must be immediately reported to the local Medical Officer of Health.¹

Immunisation is the best protection

In cases of highly infectious vaccine-preventable diseases such as measles, mumps and rubella, a high percentage of the population needs to be fully immunised to prevent wide-spread community transmission (Table 2).¹ With a basic reproduction number (R0) of 12 – 18, measles is one of the most contagious and communicable of all infectious diseases.^{1, 15} Influenza and coronavirus disease 2019 (COVID-19) have comparatively lower basic reproduction numbers (Table 1).^{1, 21}

Table 2. Disease transmissibility ratings and herd immunity thresholds required to prevent wide-spread community transmission.¹

^*R0 values are estimated values, often deriving from global averages, such is the case with COVID-19 ²¹. R0 values represent the estimated spreading potential of an infection by calculating the number of secondary cases that can be infected by one infectious case, within a given, and susceptible population.¹ Ranges can therefore vary greatly between populations depending on the means of calculation and the specific population.²¹

^†The mean R0 number of the delta variant of COVID-19 is estimated to be 5.08 (range 3 – 8)²²

First MMR dose now recommended at age 12 months

Following the 2019 measles outbreak, the National Immunisation Schedule was revised on 1 October, 2020, recommending that children now receive the first MMR dose at age 12 months, and a second dose at age 15 months (previously recommended at age 15 months and age four years).¹ MMR vaccination is fully funded for New Zealand citizens and residents, and contacts of confirmed cases, including catch-up vaccinations (see Table 3 for recommended MMR vaccination schedule).¹

Encourage immunisation of susceptible individuals

Any person born on or after 1 January, 1969, who has not received two documented doses of the combined MMR vaccine, is considered susceptible to one or more of measles, mumps and rubella, and includes those who have:^{1, 16}

• Received partial vaccination with one or two doses of a measles-only vaccine (or measles-rubella vaccine for people vaccinated overseas)
• Clinical history of infection of one or more of the diseases without further documentation of immunity (see: “Criteria for determining immunity”)

All susceptible individuals should receive one or two doses of MMR vaccine (see Table 3 for dosing recommendations).¹ If vaccination history is not available or is uncertain (i.e. number of doses and/or type of vaccine), advise patients that there is no safety concern in re-vaccinating with MMR and this is recommended.¹ However, as a live attenuated vaccine, there are certain people for whom MMR is contraindicated (see: “Contraindications and cautions”).¹

Table 3. Recommended MMR immunisation schedule. Adapted from the “Immunisation Handbook” (2020).¹

New Zealand population groups at higher risk of infection

In New Zealand, people most at risk of measles exposure and infection include those:¹

• Who are not fully vaccinated with MMR, particularly children aged under two years, and adolescents and young adults, aged between 15 and 30 years (see: “Adolescents and young adults in New Zealand are under-immunised”)¹³
• Returning from recent travel overseas with uncertain immunisation history, due to higher risk of exposure in measles-endemic countries
• Born in countries where complete vaccination with all three antigens is less likely or access is difficult
• Working in certain occupations including health care, early childhood education services and other high-contact occupations^*, who are at increased risk of both contracting and transmitting infections

^*High-contact occupations include those working in emergency and essential services such as armed forces, immigration/refugee centres, long-term care facilities, correctional facilities and border workers¹

For further information on occupation-related vaccination, see: www.health.govt.nz/our-work/immunisation-handbook-2020/4-immunisation-special-groups#4-8

MMR immunity gap increases the risk of fetal rubella infection

Although rubella cases have remained low, a large number of women falling within this immunity gap are now of childbearing age and susceptible to rubella infection, increasing the risk of fetal infection and serious complications such as CRS (see: “Rubella”).¹ Women of childbearing age, especially those who are planning pregnancy, should be asked if they are fully immunised against rubella with MMR (see Table 2 for recommended vaccination schedule if catch-up is required).¹

N.B. In New Zealand, serological testing for immunity against rubella is typically only performed as part of antenatal care and is not funded as a precautionary measure for women planning pregnancy.¹ If serology results indicate a lack of immunity during pregnancy, MMR vaccination should be given following delivery.¹

Further information on MMR immunisation catch-ups is available from: www.health.govt.nz/our-work/immunisation-handbook-2020/appendix-2-planning-immunisation-catch-ups

Further information on MMR immunisation for special groups is available from: www.health.govt.nz/our-work/immunisation-handbook-2020/4-immunisation-special-groups

Scheduling MMR with COVID-19 vaccination

The requirements for spacing between administration of mRNA COVID-19 vaccine with other vaccines, with the exception of the vaccine for herpes zoster, have been removed. Previously, it was recommended that a gap of two weeks be observed between COVID-19 vaccination and any non-live vaccine, or four weeks with a live vaccine, such as MMR.¹ If a person therefore requires MMR vaccine and also COIVD-19 vaccine, the advice is that they can now be administered concurrently, and that MMR can be given either immediately before or after COVID-19 vaccine.¹

Further information about COVID-19 vaccination is available from the Immunisation Handbook (see Section 5.4.5 for information on co-administration with other vaccines): www.health.govt.nz/our-work/immunisation-handbook-2020/5-coronavirus-disease-covid-19

Contraindications and cautions

As MMR is a live vaccine, people with contraindications include those:¹

• Who are pregnant
• Who are immunocompromised
• With proven anaphylaxis to either the vaccine itself or a component within it, e.g. gelatin or neomycin. N.B. People with egg allergies (including anaphylaxis) can safely receive the vaccine.
• Who have been immunised with another live vaccine^* within the previous four weeks; All vaccines can be given concurrently with MMR vaccine (with separate syringes and different injection sites), however, a four week gap is required for administration of any other live vaccine if not administered concurrently. There is no longer a requirement for spacing with inactivated vaccines, e.g. the COVID-19 vaccine.

^*Additional live attenuated vaccines include varicella, rotavirus, tuberculosis (BCG) and zoster¹

Further information about co-administration of MMR with other vaccines is available from the Immunisation Handbook (see Section 12.4.4) www.health.govt.nz/our-work/immunisation-handbook-2020/12-measles#11-6

Two doses are needed for full immunity

Following the second dose of MMR the serologic evidence of immunity increases to 99% against measles, 83 – 88% against mumps, and is likely higher than 90 – 97% against rubella.¹ Almost all people who do not develop protective immunity following the first MMR dose, do so after the second. Rarely, fully immune people can still contract measles following two doses, however, it is usually less severe and hospitalisation is less likely.¹

Inform patients about potential adverse reactions

Following vaccination, some patients may experience common, mild adverse reactions such as rash, fever, submaxillary gland swelling or joint pain.^{1, 23} Mild reactions typically resolve within a few days without treatment. Patients can manage symptoms by resting, drinking plenty of fluids and relieving fever or discomfort with mild analgesia if required (e.g. paracetamol or ibuprofen).^{1, 23} Advise patients to contact a health professional if they are concerned about troublesome and/or unexpected symptoms.¹

N.B. Adverse events following immunisation should be reported to the Centre for Adverse Reactions Monitoring (CARM).¹