The Ministry of Health has put out an urgent letter asking health providers to do a better job of warning people about possible serious side effects of the Covid-19 Pfizer vaccine.

It comes as the autopsy of Dunedin man Rory Nairn has found he died of vaccine-related myocarditis. Nairn died in November after experiencing myocarditis-like symptoms over nearly a fortnight.

In her assessment of the case, pathologist Noelyn Hung says: “It is my opinion that the cause of death is acute myocarditis, and in the view if the history of symptoms since covid-19 vaccination, and no other cause for myocarditis, is consistent with vaccine-related myocarditis.

"Vaccination with the first Pfizer dose had occurred 12 days earlier and myocarditis related symptomology was reported thereafter."

In a letter titled ‘Urgent update on Covid-19 Vaccine-associated Myocarditis and Pericarditis’, Director-General of Health Dr Ashley Bloomfield and other ministry authorities say there is a need “to reiterate the importance of timely assessment and management to prevent the serious consequences of myocarditis/pericarditis.”

Myocarditis and pericarditis are rare side effects that affect the heart. The rate in New Zealand is reported to be around three per 100,000 vaccinations or 0.003%, and can be treated if picked up early.

“One effects the lining around the outside of your heart - that's the pericarditis. The other effects the muscles of your heart which is the myocarditis, each of them has different investigations we can do to determine if that’s what’s going on” Royal NZ College of GPs president Dr Samantha Murton says.

Ministry of Health data shows that clinically-validated myocarditis/pericarditis in the 30-days following the vaccine occurs:

Approximately equally in both males and females

Over a wide age range, with a median age of diagnosed cases in the mid-30s

Approximately equally after dose one and after dose 21.

In this New Zealand data, the most common symptoms are:

Chest heaviness, discomfort, tightness or pain

Difficulty breathing, shortness of breath

Feeling dizzy, light-headed or faint

Racing or fluttering heart, or a feeling of ‘skipped beats’

In the letter health officials say it’s “crucial” that those getting vaccinated are aware of rare and serious potential side-effects. It says it will be updating screening questions and advice on 0800 health helplines, as well as strengthening public health advice and safety monitoring.

It’s asking all healthcare providers to review their practices around myocarditis and pericarditis and ensure the information is known by clinicians.

“Finally, could we ask you to… confirm in writing that local planning and clinical leadership is in place to guide a local response to prevent the serious consequences of undiagnosed or untreated myocarditis/pericarditis,” the letter reads.

Immunisation Advisory Centre Director Professor Nikki Turner says clinicians have been hearing of cases of people who have myocarditis-like symptoms and have been unaware that it could be related to the vaccine.

“It’s more about is our information getting to the right sources and right people. We’re vaccinating a large amount of people in this country and it’s really important that at all our sites in all places everyone who is vaccinated gets effective post-vaccination advice and then also know where to go for help if they need to.”

Experts say whether you're vaccinated or yet to get the jab - don't panic. You're much more likely to get myocarditis and pericarditis if you get Covid-19 than if you're immunised against it.

“Every side effect from the vaccination is a very small version of what your body would get from the Covid disease itself,” Dr Murton says.

“Whatever side effects happen with the vaccine, there is a vastly increased number of those side effects that happen with disease.”

“Covid causes death. We are out there trying to prevent disease and death and this vaccine is absolutely doing that,” Turner says.

The Ministry of Health refused an interview but told 1News in a statement it’s regularly communicated to the public and health professionals on the topic of myocarditis and pericarditis.