RNZ revealed yesterday that the Highbrook vaccination centre in Auckland found five doses left over on July 12.,
That meant five of the 732 people vaccinated that day may have been injected with a harmless saline dose instead. Saline is used to dilute the vaccine once it has thawed.
Dr Bloomfield told RNZ's Morning Report programme today that authorities were waiting for scientific advice on what to tell people.
"There was always the intention to tell people," he said.
"We were getting advice around whether or not we offered people a further dose.
"There was some question about that, because of the uncertainty about whether anyone had missed out in the first place.
"I'm completely committed to open disclosure on these events."
Bloomfield said all 732 people will get sent an email or have a letter couriered to them and there will be a follow-up phone call outlining their options.
"There's a group of about 25 people in that overall group who haven't had a second dose, so that's been expedited so they can have that second dose in the next couple of days.
"Everybody in the group will have had at least one full dose and and five people may have had a slightly more diluted dose, about a 20 percent dose, because there is some residual vaccine left in the empty vials. Only five doses were being drawn up from each of the vials at that time, on that day."
A third dose can be arranged further down the track if people want that, he said.
Second possible mistake
The Ministry of Health has since confirmed another possible vaccine mistake, this time at the Wigram vaccination clinic in Christchurch, where vaccine stock did not match the number of doses administered.
Bloomfield said it was a similar case, but the clinic was doing a reconciliation much more regularly so the error was picked up more immediately.
They were able to identify the six people affected, confirm they hadn't received a dose and offer them a further vaccination.
Earlier, Bloomfield said he didn't know about the Christchurch incident until after it had been reported by media and wasn't sure why he wasn't told. He said he had a good team looking after the vaccination situation.
"It wasn't one the team had told me about yet," he told Newstalk ZB's Mike Hosking.
"They don't tell me about everything... I've got a really good team that's looking after the vaccination programme. Looking at the information provided, I can see it was dealt with on the spot, very professionally."
The Covid-19 vaccination programme's national director, Jo Gibbs, said vaccine stock did not match the number of doses administered in Christchurch.
"During the full-day clinic, six vaccinations were administered with a very low dose of vaccine."
The incident occurred as a result of a vaccinator picking up a tray of six syringes that had not had the correct vaccine drawn into them, she said.
"As a result of the investigation into this event, we know the affected cohort in this case is only six people because records show it occurred between 1.20pm and 1.40pm that day."
Gibbs said all six people have been contacted by the DHB and a clinical plan was developed for each person.
Four people were receiving dose one and two people receiving dose two on July 14. They have since been given another dose of vaccine.
Woman 'disgusted' she wasn't told of possible vaccination mistake
A woman immunised at the Highbrook Vaccination Centre in Auckland is disgusted she had not been told she may have been given just saline instead of the Pfizer vaccine.
Fiona Tolich, who was vaccinated on July 12 said she was "disgusted" she had not been told about the mistake by the ministry.
She believed the ministry had no intention of telling her.
"You can't tell me they've taken five weeks talking to experts when internationally they were able to make the right call on the same day that it happened."
Tolich's partner is an essential worker and she has an underlying health condition.
She has so far only had one Covid-19 injection.
She said she can understand a mistake being made, but not knowing about it until now is appalling.
"People have a right to know what is being put in their body and they have a right to honesty and to me this screams of a lack of honesty and integrity and a lack of ethics."
She wants an apology from the ministry and an explanation.
Meanwhile, Health and Disability Commissioner Morag McDowell said she will be contacting the ministry about the incident.
"Consumers have the right to be fully informed about what may have happened to them.
"I understand that the Ministry of Health is working to resolve this matter and I expect that this will include informing the people who could have been affected by the error."
She said she will writing to the ministry to understand the actions being taken and to remind them of her expectations regarding the right of consumers to open disclosure.
