Manitobans who received AstraZeneca as their first dose of COVID-19 and meet the current second-dose eligibility criteria are now eligible to receive either mRNA — Pfizer or Moderna — vaccines as their second dose.
Dr. Joss Reimer, the province’s medical lead on the vaccination implementation task force, announced the change on Monday.
“The good news is that a Spanish study has been released that showed that people who received a second dose of an mRNA (Pfizer and Moderna) vaccine after AstraZeneca had a good immune response,” she said. “This is consistent with what we’ve seen with vaccines for other diseases as well.”
The province was originally waiting for the results from a UK. study on dose mixing. Results were initially expected at the end of May, but that date has been pushed back to late June.
Reimer said that wait would be too long, and knowing what they know about dose mixing with other vaccines, they are confident the Spanish results and other science translates to good protection.
“We’ve seen that changing products in between doses for almost every other vaccine still results in good effectiveness, and ultimately that’s what we’re after — the effectiveness of the vaccine in preventing the spread and the severity of a COVID infection,” Reimer said.
It would have been ideal to wait for the UK. study results, Reimer said, but the nature of the pandemic means an ever-changing situation and decisions need to be made with the “best information available to us.”
Second dose eligibility was expanded to anyone who received their first dose of vaccine on or before April 8, which now includes the AstraZeneca shot. Public health also announced that the date will be further expanded on Tuesday to those who were jabbed on or before April 13.
All Indigenous people ages 12 and up, and those with specific health conditions in Manitoba can book second dose appointments as long as they meet the minimum time interval between doses.
For those who got the AZ jab first, the minimum interval for a second dose of mRNA vaccine is 28 days. But Reimer said the province is recommending waiting eight-to-12 weeks in between doses, based on results from the Spanish study.
She said the manufacturer’s minimum is not the best interval, citing the emerging science, and suggested that minimum from the manufacturer is not ideal and that waiting at least eight weeks showed a stronger immune response.
“I hope this provides some clarity for people,” Reimer said. “I know if you got AstraZeneca, the not knowing has been difficult and stressful.”
The message, she said, is if you’re healthy and able to follow public health orders, wait at least eight weeks before booking.
Individuals can book online or by calling 1-844-626-8222.
The province has now administered 852,094 doses of vaccine since the campaign started in the middle of December.
To date, a total of doses 953,290 of vaccine have been delivered to Manitoba, including:
Meanwhile, the province said they had about 2,500 people show up last week for walk-in appointments for the Moderna shot at the Leila supersite. The province opened the site on Thursday and Friday without the need for an appointment.
Expiry date on remaining AZ shots extended
A submission from AstraZeneca to Health Canada to extend the expiry date on doses of the vaccine set to expire on Monday has been approved.
The new expiry date on the doses is now July 1.
Reimer said the data from AstraZeneca to Health Canada show no change in the stability of the serum.
“They submitted stability data… demonstrating that the product maintained all of the same characteristics, as expected, for a longer period of time than the original date they put on the original product,” Reimer said. “This wasn’t an assumption that Health Canada made, it really was a decision they made based on data that was given to them by AstraZeneca.”
The province has 3,700 doses of Oxford-developed vaccine, which will be used for patients who may not be able to get an mRNA vaccine as their second shot due to allergies and other medical conditions.