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dose came from a variety of real life scenarios, both in Canada and abroad, although NACI said many of the studies had not yet been peer reviewed.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

Just Posted

Victoria police are looking for a 38-year-old man after he allegedly assaulted and choked a missing 15-year-old victim in Beacon Hill Park Tuesday night. (Black Press Media file photo)
15-year-old choked in Beacon Hill tent, Victoria police assaulted while intervening

Police searching for 38-year-old suspect, two officers injured in altercation with park residents

Nanaimo-Ladysmith school district teachers’ union, and its counterparts from Mount Arrowsmith district, seek stricter COVID-19 rules. (News Bulletin file)
Nanaimo-Ladysmith teachers’ union asks for stricter COVID-19 measures

Teachers ask for vaccine, more online learning, mask mandate for primary students

Some Saanich firefighters have expressed concerns about first responders in the Island Health Region not being prioritized to receive the COVID-19 vaccine as an outbreak at a fire station would make service delivery a challenge. (Devon Bidal/News Staff)
Saanich firefighters not prioritized for COVID-19 vaccine despite working on frontlines

Saanich members express frustration, department calls on Island Health to take action

A total of 10 flight exposures have affected the Victoria International Airport in April so far, making it the highest monthly total since the start of the pandemic. (Black Press Media file photo)
Victoria hits record-breaking number of monthly COVID-19 flight exposures

As of April 21, 10 flight exposures reported for the month

Former University of Victoria rowing coach Barney Williams is photographed in the stands during the Greater Victoria Invitational at CARSA Performance Gym at the University of Victoria in Victoria, B.C., on Friday, November 29, 2019. THE CANADIAN PRESS/Chad Hipolito
Rowing Canada sanctions former head coach of UVic varsity women’s team

Suspension of Barney Williams would be reversed if he complies with certain terms

A large crowd protested against COVID-19 measures at Sunset Beach in Vancouver on Tuesday, April 20, 2021. (Snapchat)
VIDEO: Large, police-patrolled crowds gather at Vancouver beach for COVID protests

Vancouver police said they patrolled the area and monitored all gatherings

FILE – The Instagram app is shown on an iPhone in Toronto on Monday, March 19, 2018. THE CANADIAN PRESS/Graeme Roy
Judge acquits B.C. teen boy ‘set up’ on sex assault charge based on Instagram messages

The girl and her friends did not have ‘good intentions’ towards the accused, judge says

Kai Palkeinen recently helped a car stuck on the riverbed near the Big Eddy Bridge. While the car could not be saved, some of the driver’s belongings were. It’s common for vehicles to get stuck in the area due to significantly changing river levels from Revelstoke Dam. (Photo by Kai Palkeinen)
“I just sank a car’: Revelstoke resident tries to save vehicle from the Columbia River

Although it’s not permitted, the riverbed near the city is popular for off roading

Meng Wanzhou, chief financial officer of Huawei, walks down the street with an acquaintance after leaving B.C. Supreme Court during a lunch break at her extradition hearing, in Vancouver, B.C., Thursday, April 1, 2021. A judge is scheduled to release her decision today on a request to delay the final leg of hearings in Meng Wanzhou’s extradition case. THE CANADIAN PRESS/Rich Lam
B.C. judge grants Meng Wanzhou’s request to delay extradition hearings

Lawyers for Canada’s attorney general had argued there is no justification to delay proceedings in the case

B.C. Premier John Horgan announces travel restrictions between the province’s regional health authorities at the legislature, April 19, 2021. (B.C. government photo)
B.C. sees 862 more COVID-19 cases Wednesday, seven deaths

Recreational travel restrictions set to begin Friday

B.C. Finance Minister Selina Robinson is photographed following her budget speech in the legislative assembly at the provincial legislature in Victoria, Tuesday, April 20, 2021. THE CANADIAN PRESS/Chad Hipolito
B.C. budget lacks innovative drive, vision during uncertain times, say experts

Finance Minister Selina Robinson’s budget sets out to spend $8.7 billion over three years on infrastructure

Using panels kept cold by water circulating within them, B.C. researchers compared thermal comfort in 60 of the world’s most populous cities, including Toronto. (Lea Ruefenacht)
B.C. researchers use air conditioning to combat spread of COVID particles

Dr. Adam Rysanek and his team have proven a new worthwhile system – a mixture of cooling panels and natural ventilation

Police road checks are coming for people travelling between regions while COVID-19 travel restrictions are in place. (Black Press file photo)
B.C. clarifies COVID-19 travel restrictions, Lower Mainland a single zone

Vehicle checks on highways, at ferry terminals to start Friday

(Black Press Media file photo)
Saanich calls for non-police security for mental health patients at hospitals

Saanich police spent nearly 1,200 hours waiting with patients at hospitals in 2020

Most Read