N.B. COVID-19 roundup: Top doctor defends vaccine mixing after WHO warning causes confusion

·8 min read
Dr. Jennifer Russell, New Brunswick's chief medical officer of health, says vaccine interchangeability is not a new concept. (Government of New Brunswick - image credit)
Dr. Jennifer Russell, New Brunswick's chief medical officer of health, says vaccine interchangeability is not a new concept. (Government of New Brunswick - image credit)

New Brunswick's chief medical officer of health is defending the province's approach to mixing COVID-19 vaccines from different manufacturers for first and second doses after a warning from the World Health Organization's lead researcher Monday caused confusion.

Dr. Jennifer Russell said the province is following the June 1 recommendations of the National Advisory Committee on Immunization (NACI) on the interchangeability of authorized COVID-19 vaccines.

NACI "reviewed all available evidence from ongoing studies monitoring the mixing of COVID-19 vaccines and evidence on the safety of mixing COVID-19 vaccines was available from studies," she said in an emailed statement.

NACI's recommendations say it's safe and effective for people to receive an mRNA vaccine — either Pfizer-BioNTech or Moderna — as a second dose if their first dose was AstraZeneca-Oxford.

For people whose first dose was Pfizer or Moderna, NACI recommends they take either of the two products as a second dose if the same first product isn't "readily available" or is unknown because they both use a similar mRNA technology.

"No data currently exist on the interchangeability of COVID-19 mRNA vaccines. However, there is no reason to believe that mRNA vaccine series completion with a different authorized mRNA vaccine product will result in any additional safety issues or deficiency in protection," the recommendations state.

The advisory body defines readily available as "easily available at the time of vaccination without delay or vaccine wastage."

New Brunswick has been mixing first and second doses of AstraZeneca and Pfizer, as well as Moderna as it continues to push to reach its goal to have 75 per cent of the eligible population fully vaccinated by Aug. 2.


On Monday, during a global online briefing, WHO's chief scientist Dr. Soumya Swaminathan appeared to warn against mixing vaccines.

"It's a little bit of a dangerous trend here. We are in a data-free, evidence-free zone as far as mix and match," she said as part of a lengthy response to a question about the need for booster doses, following Pfizer's announcement that it's seeking the U.S. Food and Drug Administration's approval to manufacture and distribute third doses.

"There is limited data on mix and match," she said. "There are studies going on. We need to wait for that and maybe it will be a very good approach."

But as it stands, there is only data on using Pfizer after AstraZeneca, said Swaminathan.

"So it will be a chaotic situation in countries if citizens start, you know, deciding when and who they should be taking a second, or a third or a fourth dose."

She later clarified her remarks in an overnight tweet, saying she warned people against deciding for themselves to mix and match.

"Public health agencies can, based on available data. Data from mix and match studies of different vaccines are awaited — immunogenicity and safety both need to be evaluated."

WHO's strategic advisory group on vaccines updated its recommendations last month to say the Pfizer vaccine can be used as a second dose after a first dose of AstraZeneca if a second dose of AstraZeneca vaccine is "not available due to supply constraints or other concerns."

A clinical trial led by the University of Oxford in the U.K. is also underway to investigate mixing the regimen of AstraZeneca and Pfizer. This trial was recently expanded to include the Moderna and Novovax vaccines, a WHO spokesperson said.

"Vaccine interchangeability is not a new concept," said Russell. "Similar vaccines from different manufacturers are used when vaccine supply or Public Health programs change. Different vaccine products have been used to complete a vaccine series for influenza, hepatitis A, and others."

"Completing your vaccine series by getting a second dose is essential to achieve optimal and longer-lasting protection against COVID-19 disease and associated severe outcomes," she said.

Nathan Denette/The Canadian Press
Nathan Denette/The Canadian Press

More results from ongoing studies on mixing COVID-19 vaccines are expected in the coming months, according to the Public Health Agency of Canada, including this Canada-wide research study.

Canada has been mixing COVID-19 vaccines for weeks based on emerging research from Spain and the United Kingdom that found combining AstraZeneca with Pfizer shots was both safe and effective.

"There is a possibility of increased short-term side-effects when mixing COVID-19 vaccines, including headache, fatigue and feeling ill. This was particularly noted with a short interval of [four] weeks between the first and second dose," according to an emailed statement. "These side-effects are temporary and resolve without complications."

No evidence of need for booster

WHO will make recommendations on booster doses when it thinks they are needed, said Swaminathan.

"It may well be that you need boosters after a year or two years, but at this point, after six months after the primary dose, there doesn't seem to be any indication," she said.

Four countries have already announced a booster program and a few more are thinking about it, she said.

If 11 "high and upper-middle income countries" decide to provide a third dose to their populations, or even only to subgroups, an extra 800-million doses will be required, Swaminathan said.

Meanwhile, there are some countries where front-line health-care workers and the elderly, who are most vulnerable, have not been vaccinated, she said.

"At this point … there is no scientific evidence to suggest boosters are definitely needed."

WHO's recommendation will be based on science and data, "not on individual companies declaring that their vaccines should now be administered as a booster dose."

0 new cases, 0 in hospital

New Brunswick reported no new cases of COVID-19 on Tuesday for the eighth straight day, and no one in the province is hospitalized with the respiratory disease for the first time in nearly six months.

Fifty-two per cent of New Brunswickers aged 12 and older are also now fully vaccinated, the COVID-19 dashboard shows.

"To achieve our next target of fully vaccinating 75 per cent of eligible New Brunswickers, we need people to continue to roll up their sleeves," Dr. Jennifer Russell, the province's chief medical officer of health, said in a statement.

"I encourage anyone who hasn't booked an appointment to do so now and help us move closer to our final phase on our path to green."

Once the threshold is reached, the state of emergency mandatory order will end and all Public Health restrictions will be lifted, provided COVID hospitalizations remain low and all health regions remain at the yellow COVID alert level.

Evan Mitsui/CBC
Evan Mitsui/CBC

The province's goal is to reach the target by Aug. 2, New Brunswick Day.

Another 6,936 second doses of vaccines were administered Monday, meaning 360,545 New Brunswickers aged 12 or older have received two doses.

The first dose vaccination rate has also inched up again, to 79.7 per cent, with 911 more first doses administered Monday.

Public Health is holding more mobile walk-in Moderna clinics this week to help make getting first and second doses more convenient. Two clinics are underway Tuesday:

  • Fredericton — Marysville Walk-in Clinic, 231 Canada St., on Tuesday, between noon and 6 p.m.

  • Hillsborough — Kiwanis Community Centre, 47 Legion St., on Tuesday, between 11 a.m. and 6 p.m.

The other clinics include:

  • Perth-Andover — River Valley Civic Centre, 11 School St., on Thursday, between noon and 6 p.m.

  • Dorchester — Dorchester Veterans Community Hall, 4955 Main St., on Thursday, between 10 a.m. and 4 p.m.

  • Plaster Rock — Tobique Lions Community Centre, 61 Everett Lane., on Friday, between 10:30 a.m. and 4 p.m.

  • Salisbury — Salisbury Baptist Church, 3128 Main St., on Friday, between 10 a.m. and 4 p.m.

Anyone over the age of 12 is eligible to receive a COVID-19 vaccine. They can book an appointment online through a Horizon or Vitalité health network clinic or through a participating pharmacy.

They are asked to bring their Medicare card, a signed consent form, and for those receiving a second dose, a copy of the record of immunization they received after getting their first dose.

People who booked an appointment but were able to get vaccinated sooner elsewhere are asked to cancel the appointment they no longer need.

4 active cases

New Brunswick has four active cases of COVID-19, Public Health reported Tuesday.

Since Monday, there has been one more recovery and no one is now in hospital.

The last time the province had no hospitalized COVID patients was Jan. 12, said Department of Health spokesperson Bruce Macfarlane.


There have been 2,336 confirmed cases of COVID-19 in New Brunswick since the pandemic started, with 2,285 recoveries so far and 46 COVID-related deaths.

A total of 370,042 tests have been conducted, including 878 on Monday.

Atlantic COVID roundup

Nova Scotia reported one new case of COVID-19 on Tuesday, and has 31 active cases.

Newfoundland and Labrador has no new COVID-19 cases on land, but a second ship is now anchored in Conception Bay with cases on board. The province has 20 active cases, 19 of which involve people on the two ships.

Prince Edward Island has no new cases or active cases.

What to do if you have a symptom

People concerned they might have COVID-19 can take a self-assessment test online.

Public Health says symptoms of the illness have included a fever above 38 C, a new or worsening cough, sore throat, runny nose, headache, a new onset of fatigue, and difficulty breathing.

In children, symptoms have also included purple markings on the fingers and toes.

People with one of those symptoms should stay at home, call Call Tele-Care 811 or their doctor, and follow instructions.

Our goal is to create a safe and engaging place for users to connect over interests and passions. In order to improve our community experience, we are temporarily suspending article commenting