THE CANADIAN PRESS/Darryl Dyck

THE CANADIAN PRESS/Darryl Dyck

NACI doubles down on 4-month gap, says 75% of Canadians could get COVID jab by mid-June

Committee says 75% of Canadians can be vaccinated by mid-June

The National Advisory Committee on Immunization has doubled down on its recommendation of a four-month gap between doses of COVID-19 vaccines in an update released Wednesday (April 7).

In the update, NACI said that delaying the second dose until everyone has received their first dose would allow 75 per cent of Canadians to get it by mid-June.

“Second doses should be offered as soon as possible after all eligible populations have been offered first doses, with priority given to those at highest risk of severe illness and death from COVID-19 disease,” NACI said. “With Canada’s expected vaccine supply, the interval between the first and second dose is expected to be less than four months.”

NACI said that provinces could choose to shorten the time between doses in certain populations based on local cases, vaccine supply and new evidence. The committee first made the four-month gap recommendation in March, citing vaccine availability.

Evidence for delaying the second dose came from a variety of real life scenarios, both in Canada and abroad, although NACI said many of the studies had not yet been peer reviewed.

“Effectiveness data from Canada and the UK demonstrates protection from the mRNA vaccines based on analyses extending to about 8 weeks from vaccination,” NACI said.

“Experience with other multi-dose vaccines after a single dose suggests protection could last for six months or longer in adolescents and adults (e.g., hepatitis A and human papillomavirus vaccines).”

NACI said that as a “general vaccination principle,” interrupting an immunization schedule doesn’t require redoing the first dose.

“Furthermore, a longer interval between the priming and boosting doses allows maturation of the memory B cells, resulting in a higher and more durable response.”

NACI said that current evidence shows 92 per cent efficacy for the Pfizer and Moderna mRNA vaccines and 76% efficacy for the AstraZeneca viral vector vaccine.

“Effectiveness has been documented for up to two months after the first dose of the mRNA vaccines, and the AstraZeneca clinical trial publication modelled one-dose efficacy up to 90 days after vaccination,” NACI said.

Data from long-term care residents in B.C. showed vaccine effectiveness of 87 per cent between 21 and 54 days after the first dose, while other data provided by the B.C. Centre for Disease Control showed effectiveness of 80 per cent from 21 to 43 days after the first dose in long-term care residents. Similar immunization intervals in health-care workers showed similar results.

NACI said that data from the AstraZeneca clinical trial showed maximum efficacy when the interval between doses was extended to over 12 weeks. Efficacy at less than six weeks after the first dose was at about 55 per cent, while efficacy 12 weeks after the first dose was at 81 per cent.

B.C. has used Pfizer, and to a less extent Moderna, in its age-based vaccination program, as well as for health-care workers. AstraZeneca was initially being used for frontline workers, but after concerns over effectiveness in older adults and blood clots in younger people, B.C. moved to using it to vaccinate 55 to 65 year old via community pharmacies.


@katslepian

katya.slepian@bpdigital.ca

Like us on Facebook and follow us on Twitter.

Want to support local journalism during the pandemic? Make a donation here.

Coronavirus

Get local stories you won't find anywhere else right to your inbox.
Sign up here

Just Posted

Photo collage of loved ones lost to substance use and overdose. (Photo courtesy Moms Stop The Harm)
B.C. overdose deaths still rising 5 years after public health emergency declared

Moms Stop the Harm calls on B.C. to provide safe supply in response to deadly illicit drug use

Burning will only occur if weather conditions are suitable and allow smoke to dissipate. (Priyanka Ketkar photo/Lakes District News)
Pile burning of 50 wood debris in Burns Lake community forest

Smoke might be visible for Burns Lake and neighboring areas

Tourism update Meghan Olson. (Priyanka Ketkar photo/Lakes District News)
Village of Burns Lake gets a new tourism coordinator

Meghan Olson, a Burns Lake local, replaces the former coordinator

COVID 19 cases in the province between Mar. 28 to Apr. 3. (BC CDC photo/Lakes District News)
No new COVID-19 cases in Burns Lake

Weekly COVID-19 cases decline in Northwest B.C.

Nee Tahi Buhn band
Nee Tahi Buhn Band chief and council removed

Interim council working towards a by-election

Demonstrators at the legislature on April 14 called on the province to decriminalize drug possession and provide widespread access to regulated safe supply across B.C. (Jake Romphf/News Staff)
Rally calls for decriminalization, safe supply on 5th anniversary of overdose emergency declaration

From 2016 to the end of February, 7,072 British Columbians died due to overdose

(Government of Canada)
Liberal MP caught stark naked during House of Commons video conference

William Amos, in Quebec, appeared on the screens of his fellow members of Parliament completely naked

Provincial health officer Dr. Bonnie Henry updates B.C.’s COVID-19 situation at the B.C. legislature, Feb. 1, 2020. (B.C. government)
B.C.’s COVID-19 case count jumps to 1,168 Wednesday, nearly 400 in hospital

Now 120 coronavirus patients in intensive care, six more deaths

Moss covered branches are seen in the Avatar Old Growth Forest near Port Renfrew on Vancouver Island, B.C. Thursday, Sept. 29, 2011. THE CANADIAN PRESS/Jonathan Hayward
B.C. blockades aimed at protecting old-growth forests reveal First Nation split

Two Pacheedaht chiefs say they’re ‘concerned about the increasing polarization over forestry activities’ in the territory

Richmond RCMP Chief Superintendent Will Ng said, in March, the force received a stand-out number of seven reports of incidents that appeared to have “racial undertones.” (Phil McLachlan/Capital News)
‘Racially motivated’ incidents on the rise in B.C’s 4th largest city: police

Three incidents in Richmond are currently being invested as hate crimes, says RCMP Chief Superintendent Will Ng

Commercial trucks head south towards the Pacific Highway border crossing Wednesday (April 14, 2021). The union representing Canadian border officers wants its members to be included on the frontline priority list for the COVID-19 vaccine. (Aaron Hinks photo)
CBSA officers’ union calls for vaccine priority in B.C.

Border officers at ports including, YVR and land crossings should ‘not be left behind’

A still from the video taken of a violent arrest on May 30, 2020 in downtown Kelowna. (File)
Kelowna Mountie charged with assault for caught-on-camera violent arrest

Const. Siggy Pietrzak was filmed punching a suspected impaired driver at least 10 times during an arrest

A screenshot from a Nuu-chah-nulth healing song and performance created in collaboration between Hjalmer Wenstob and Timmy Masso. (Screenshot from YouTube)
VIDEO: Tla-o-qui-aht First Nation brothers produce COVID-19 healing song

Hjalmer Wenstob and Timmy Masso share dance and inspiration.

Most Read