Updated Recommendations for Measles Vaccination

In 2014, the World Health Organization (WHO) declared measles to be eliminated in Australia. While no longer endemic, imported cases of measles still occur which can lead to localised outbreaks. A total of 108 measles cases have been reported to the National Notifiable Diseases Surveillance System in Australia so far this year compared to 103 for the whole of 2018.

Measles has an estimated basic reproduction number (R₀) in the range of 12-18. This means that an average of 12 to 18 secondary infections are expected following one typical case in a totally susceptible population. Due to the highly contagious nature of this virus, Australia has an immunisation coverage target of 95%.

It is recommended that individuals receive two doses of measles-containing vaccine, with the first dose administered at 12 months of age. However, a recent update to the Australian Immunisation Handbook advises that the first dose may be given to infants as young as six months of age in special circumstances. Special circumstances include travel to highly endemic areas, during outbreaks, and as post-exposure prophylaxis.

A recent study suggests that infants vaccinated against measles between six and eight months of age have lower long-term immunity to measles compared to infants who receive their first dose between nine and 12 months of age. At 14 months of age, 20% of children in the early vaccination group had antibody concentrations below the cut-off for clinical protection compared to 0% in the group vaccinated later. This effect persisted for the duration of the study with 11.1% of the early vaccinated group vaccinated early not achieving clinically protective antibody levels three years after their booster compared to 0% of the group vaccinated later. The Australian Immunisation Handbook advises that infants who receive an early dose of measles-containing vaccine should receive two additional doses on the recommended schedule.