The Ministry of Education has warned schools that several are being targeted by opponents of the national vaccination programme for Covid-19.

Regular bulletins published for school leaders have had to address misinformation since March last year.

The June update, however, specifies the department is aware of reports some influential leaders such as principals were opposing vaccination.

"Individual principals may choose not to be vaccinated but they should not be advocating views in opposition to the director general of health," the bulletin reads.

The department's Secretary for Education Iona Holsted told the Herald the June update encouraged the education community to keep using the appropriate sources for verified information.

Holsted said a small number of schools were concerned about vaccination misinformation being shared in their communities.

She wanted to remind everyone that potentially wrong or misleading information can be reported to CERT NZ.

That includes anything on social media.

Holsted said school leaders hold a "respected and trusted role" in their communities and throughout the pandemic had done a great job keeping their communities updated with accurate health information.

"While individuals may choose not to be vaccinated, we would all be very concerned if any senior and influential member of the education community was speaking out against the advice of the director general of health," she said.

The warning to principals comes after tens of thousands of pamphlets airing conspiracy theories have been circulated in the public, as well as claims made online.

Last month, an organisation attacking public faith in New Zealand's Covid-19 strategy claimed it had raised $50,000 towards printing two million virus "fact" flyers to be dropped nationwide - and it is considering printing more.

The flyers, which Voices For Freedom intends to deliver to every letterbox in the country, outlines multiple conspiracy theories about Covid-19 vaccines and their effects. Their contents have been described as "misleading" and in some cases "palpably false".

Voices For Freedom co-founder Claire Deeks claimed $50,000 had been raised from "hundreds of donors" for the mass drop.

People across the country have contacted the Herald, saying they had received the flyer. A mass printing retailer estimated the cost of printing two million of these flyers would be about $30,000.

When asked when she expected the entire two million flyers to be delivered, Deeks said the flyer drop would end when there were no more flyers, before suggesting more could be printed.

University of Otago clinical microbiologist and immunologist James Ussher said it was disappointing to see such harmful information spread across the country.

"These claims are misleading and misrepresent the reality of the situation, and many of them are palpably false," he said.

Ussher, the scientific director of Vaccine Alliance Aotearoa New Zealand, said the Pfizer vaccine - which was being used in Aotearoa - was shown to be extremely safe with more than 130 million doses administered in the United States alone with no evidence of unmanageable side-effects.

Ussher said these flyers undermined trust in the vaccine which put New Zealand's future in jeopardy as borders slowly reopened, inevitably bringing the virus back into the community.