Dunedin plumber Rory Nairn died from myocarditis caused by the Pfizer Covid-19 vaccine, a coroner has found.

It is the second death ruled to have been caused by the vaccine.

Nairn, 26, collapsed in the bathroom of the home he shared with his fiancée, Ashleigh Wilson, early on November 17, 2021.

Twelve days earlier he had received his first dose of the Pfizer Covid-19 vaccine.

A coroner's inquest last month heard he reported feeling heart flutters in the days following, but put it down to stress.

Nairn was never warned about the risk of myocarditis.

Myocarditis is rare following vaccination, with international data showing 1 to 13 cases per 100,000 vaccine doses.

It is a rare disease caused by many things, including viral infection. About 95 people with myocarditis are seen in hospitals in New Zealand each year.

It is also treatable, with better outcomes if symptoms are picked up early and treatment begins early.

Coroner Sue Johnson this morning released her first findings into the death, determining the vaccine caused Nairn's death.

"I find that Rory James Nairn, aged 26, died on 17 November 2021 at ... Dunedin. The cause of his death was myocarditis, due to vaccination with the Comirnaty TM Pfizer/BioN Tech Covid-19 vaccine," the coroner says.

"My inquiry into Rory's death is not yet concluded. I have yet to establish the circumstances of his death."

Johnson still has to determine if she needs to make recommendations or comments which could help prevent similar deaths occurring in future.

She says she needs to be certain to a higher standard of proof than that which would normally satisfy a coroner.

"I consider that the seriousness of a finding that vaccination with the Covid-19 vaccine caused Rory's death requires a degree of proof in keeping with the seriousness of that finding.

"This is consistent with the principle that the graver the allegation, the clearer, more cogent and more exacting the evidence must be," the coroner says.

She defers to the expertise of pathologist Dr Noelyn Hung, who performed the post-mortem on Nairn's body.

"She saw mild atherosclerosis of the aorta and a small congenital Meckel's diverticulum (slight bulge) in the small intestine. In her expert opinion neither of these was related to Rory's death," the coroner said.

Dr Hung had previous experience with myocarditis deaths, mainly when working as a paediatric pathologist in Toronto, Canada.

The pathologist performed tests to determine the cause of death and found no sign of any infection or any other reason for Nairn's death other than in the myocardium - a layer of muscle in the heart.

"I accept Dr Hung's medical opinion that the direct cause of Rory's death was acute myocarditis and that in the absence of any other cause for the myocarditis being identified by the numerous tests that Dr Hung carried out or caused to be carried out, the myocarditis is consistent with vaccine-related myocarditis," says Johnson.

"I am satisfied that Dr Hung's evidence is sufficiently clear, cogent and exacting for me to infer from it that vaccination with the Covid-19 vaccine caused the myocarditis from which Rory died."

-RNZ.