More vaccinations are on the way to Canterbury, where health professionals are dealing with a measles outbreak.

There's a push to vaccinate more than 100,000 people in the region in the next few weeks.

So far, 25 people have contracted the highly contagious disease, with a third aged 29 to 50.

Prime Minster Jacinda Ardern says it's a timely reminder.

“This is just another strong message. People cannot rely on others being immunised to protect them. We need to encourage people to take up immunisation.”

The Law Society has also issued a notice to its staff and lawyers in Christchurch, as a police prosecutor there is one of the people infected.

Vaccinologist Helen Petousis-Harris told Larry Williams that measles is the most infectious disease known to man.

"If you can imagine that everyone is susceptible and one person gets the disease, they can go on and infect 12 to 18 other people." 

She says it is irresponsible of parents to send their un-vaccinated kids to schools, as they are putting other children at risk as well. 

However, Petousis-Harris does not believe we should become as "draconian" as having to implement compulsory baccinations. 

She says that people under the age of 50 should be most concerned.

“If you’re under 50 and you haven’t had measles and you haven’t had two doses of the measles vaccine, scuttle off to the doctor and get sorted. This is the group where we have a whole lot of gaps in our immunity. We have quite low coverage of in people of those age groups." 

She says that people who were born before 1969 were well exposed to the measles virus before the vaccine came in. 

"Because we haven't done well enough with our coverage, we've still had it circulating." 

She says people can have the vaccine again if they have not had it already.