After the topic of vaccinating kids has become more controversial online, Facebook has decided it will tackle the issue by diminishing anti-vaxxers ideas on social media.

Facebook has announced it will take steps into preventing vaccine misinformation being spread on social media.

It will do this by reducing its distribution and providing people with authoritative information on the topic.

Such steps from Facebook include:

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• Pages and groups that spread misinformation about vaccinations will not appear in searches and recommendations and will be lower ranked on people's newsfeeds.

• Facebook will reject advertisements that contain misinformation about vaccinations and an account may be disabled if the types of ads continue.

• Not show or recommend content that contains misinformation about vaccinations on Instagram Explore or hashtag pages

"We are exploring ways to share educational information about vaccines when people come across misinformation on this topic," Facebook vice-president of global policy management Monika Bickert said.

"We are fully committed to the safety of our community and will continue to expand on this work.

"Leading global health organisations, such as the World Health Organization and the US Centers for Disease Control and Prevention, have publicly identified verifiable vaccine hoaxes. If these vaccine hoaxes appear on Facebook, we will take action against them."

Many Kiwis parents are part of anti-vaccination Facebook groups such as "Anti-Vaccination Pregnancy Support Group", "NZ Natural Immunity" and "WAVES - Warnings About Vaccine Expectations".

However, Facebook said it is going to work hard to point people to pages with reliable information.

"We are exploring ways to give people more accurate information from expert organisations about vaccines at the top of results for related searches, on pages discussing the topic, and on invitations to join groups about the topic," said Bickert.

"We will have an update on this soon."

District health boards also have anti-vaxxers in their sights, saying diseases almost eradicated in New Zealand are being seen again.

Chief executive Helen Mason said while the DHBs had achieved five of the six health targets set by the previous government, "immunisation hasn't moved and has actually deteriorated. It really, really worries us."

Waikato DHB interim chief executive Derek Wright said it needed to be pushed as a public health message.

"We're seeing things like measles, we're seeing a whole lot of things that we'd almost eradicated," he told the committee.

"We've got a group of people who just refuse to have their kids vaccinated for philosophical reasons."

He said there was no particular "type" of parent who chose not to immunise.

"It's across the various different areas. It's people who are extremely well-educated. It's people who are probably struggling at times as well.

"The anti-vax people have done a really good job of raising concerns. I think it needs a national message, we actually need to be pushing it. There is some good science out there, we need to be using it," he said.

DHBs with the highest immunisation opt-outs and declines at age 8 months as at December 2018

West Coast: 16.3%
Northland: 12.7%
Lakes: 9.9%
Bay of Plenty: 9.6%
Nelson/Marlborough: 8.9%
Whanganui: 8.7%
Tairawhiti: 8.2%