TORONTO - An Ontario science teacher accused of telling his high school students they could die as a result of vaccination had a history of pushing anti-vaccine theories, a disciplinary hearing heard Tuesday.

A public health nurse who went to the school in Waterford, Ont., to administer vaccines nearly two years ago told the Ontario College of Teachers that she felt threatened by Timothy C. Sullivan, a teacher who confronted her repeatedly that day.

Angela Swick said Sullivan accused her of withholding information from students about the shots they were receiving and tried to interfere with her work.

The school's principal, meanwhile, testified that parents and students have complained about Sullivan's views on vaccination in the past, adding the teacher tells his pupils there is a link between vaccines and autism - a view that is widely denounced by the scientific community.

The school cannot be named due to a publication ban protecting the identities of students.

Sullivan is accused of professional misconduct for telling students vaccines could have fatal side effects and allegedly shouting at the nurse during her visit on March 9, 2015. He was suspended without pay for one day in April 2015.

He denies the allegations, and said Tuesday his issue is with informed consent rather than the vaccines themselves.

"I am pro informed consent, pro science and pro asking questions," he said during a break in the hearing.

Swick, a nurse with the Haldimand-Norfolk Health Unit, said Sullivan shouted at her and her colleagues when they visited the school, accusing her of keeping students in the dark about vaccines.

She described several encounters with Sullivan she said left her feeling "uneasy."

The teacher came into the cafeteria as she and her colleagues were administering four different types of vaccines and demanded information about the drugs, she said.

"He then turned around, came back and put his hands in front of me (on the desk) and said 'I hope you're letting these students know these vaccines could cause death,"' Swick told the hearing.

Swick said she immediately texted her supervisor because she worried there would be more interactions with Sullivan as the day went on.

He did in fact return, she said, and "asked the kids if they knew what was in the vaccine and shouted at them not to get it."

Swick said she alerted the principal, who came to the cafeteria with another teacher who watched the side door for signs of Sullivan.

The third encounter was more of the same, she said.

"We felt really intimidated and scared," Swick said. "We go into the school to do a service, we feel fortunate to go into schools - we just didn't have an encounter like this before."

Sullivan, who is representing himself, peppered Swick with questions about informed consent during his cross-examination, asking the nurse whether she told students about rare, but potentially serious side effects.

Swick said she doesn't warn students about vaccines' serious side effects as part of her routine. But, she said, she will inform students of certain side effects if it appears relevant based on the student's answers to her screening questions.

"If they are on heart medication, then we move onto something like hypertension," Swick said.

The nurse said she is worried about going back to the same school for another clinic next week, but noted additional staff will attend.

Brian Quistberg, the principal at the school at the time of the incident, said Sullivan's behaviour towards the nurse and her colleagues went "way over the line."

The teacher visited the school cafeteria three times - twice while during class - and "it was not his place" to be anywhere near the vaccine clinic, Quistberg said, noting he told Sullivan not to return after the first incident.

He said the nurses were afraid. "They were upset and worried, so much so that they were worried it would escalate further," the principal said.

Quistberg also read out notes from students and teachers who complained about Sullivan's teachings surrounding vaccines, which he said were dangerous due to the amount of aluminum contained in them.

After the hearing, Sullivan told reporters he will continue to talk to his students about vaccines.

"It would be irresponsible to tell them about all the benefits without the side effects," he said.

The hearing is scheduled to resume Wednesday with Sullivan taking the stand in his defence.