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dose came from a variety of real life scenarios, both in Canada and abroad, although NACI said many of the studies had not yet been peer reviewed.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

Cariboo Chilcotin Conservation Society communications officer Brianna van de Wijngaard reflects on World Water Day March 22. (Photo submitted)
DOWN TO EARTH: World Water Day means something different for everyone

This year’s World Water Day theme was Valuing Water

Williams Lake Cycling Club president Shawn Lewis (from left), Jeremy Stoward of New Path Forestry, WLCC Boitanio Bike Park director Andrew Hutchinson accept a cheque from Williams Lake and District Credit Union investment specialist Abigail King. (Photo submitted)
Williams Lake Cycling Club gets bike park donation to bolster upgrades, maintenance

Plans are to complete three rideable lines each year, he added

Forestry Ink columnist Jim Hilton. (File photo)
FOREST INK: Credit, COVID and climate crises facing the world

Concerning COVID, Mr. Carney feels we have had the proper response by showing solidarity

Columnist David Zirnhelt’s grandsons practice some fun roping on his granddaughter at the family ranch. (David ZIrnhelt photo - Williams Lake Tribune)
RANCH MUSINGS: Roping, is that an essential skill for a ranch hand?

We all know someone who has had a digit reducing accident while roping

School District board members discuss business at a regular board meeting prior to the pandemic. (Angie Mindus/Williams Lake Tribune file photo)
Ministry of Education gives special shout out to School District 27 at start of Education Week

District board and administration recognized for creating outdoor learning spaces

B.C. Health Minister Adrian Dix and Premier John Horgan describe vaccine rollout at the legislature, March 29, 2021. (B.C. government)
1,262 more COVID-19 infections in B.C. Friday, 9,574 active cases

Province’s mass vaccination reaches one million people

Cannabis bought in British Columbia (Ashley Wadhwani/Black Press Media)
Is it time to start thinking about greener ways to package cannabis?

Packaging suppliers are still figuring eco-friendly and affordable packaging options that fit the mandates of Cannabis Regulations

People walk past the Olympic rings in Whistler, B.C., Friday, May 15, 2020. Whistler which is a travel destination for tourists around the world is seeing the effects of travel bans due to COVID-19. THE CANADIAN PRESS/Jonathan Hayward
Adults living, working in Whistler, B.C., eligible for COVID-19 vaccine on Monday

The move comes as the province deals with a rush of COVID-19 and variant cases in the community

RCMP crest. (Black Press Media files)
UPDATE: RCMP investigating after child, 6, dies at motel in Duncan, B.C.

The BC Coroners Service is conducting its own investigation into the circumstances around the child’s death

RCMP display some of the fish seized from three suspects who pleaded guilty to violating the Fisheries Act in 2019, in this undated handout photo. THE CANADIAN PRESS/HO - RCMP
3 banned from fishing, holding licences after overfishing violations near Vancouver Island

Mounties seized the group’s 30-foot fishing vessel and all equipment on board at the time

B.C. Premier John Horgan responds to questions during a postelection news conference in Vancouver, on Sunday, October 25, 2020. British Columbia’s opposition Liberals and Greens acknowledge the COVID-19 pandemic has presented huge challenges for Horgan’s government, but they say Monday’s throne speech must outline a coherent plan for the province’s economic, health, social and environmental future. THE CANADIAN PRESS/Darryl Dyck
Horgan’s NDP to bring in throne speech in B.C., Opposition wants coherent plan

Farnworth said the budget will include details of government investment in communities and infrastructure

FILE - An arena worker removes the net from the ice after the Vancouver Canucks and Calgary Flames NHL hockey game was postponed due to a positive COVID-19 test result, in Vancouver, British Columbia, in this Wednesday, March 31, 2021, file photo. As vaccinations ramp up past a pace of 3 million a day in the U.S, the NHL is in a tougher spot than the other three major North American professional sports leagues because seven of 31 teams are based on Canada. (Darryl Dyck/The Canadian Press via AP, File)
Vancouver Canucks scheduled to practice Sunday, resume games April 16 after COVID outbreak

Canucks outbreak delayed the team’s season by eight games

Most Read