FILE – Healthcare workers from Women’s College Hospital prepare doses of the Moderna COVID-19 vaccine at a pop-up vaccine clinic in Toronto on Saturday, April 17, 2021. THE CANADIAN PRESS/Cole Burston

FILE – Healthcare workers from Women’s College Hospital prepare doses of the Moderna COVID-19 vaccine at a pop-up vaccine clinic in Toronto on Saturday, April 17, 2021. THE CANADIAN PRESS/Cole Burston

1st dose of mRNA vaccines stops 65% of COVID infections, protects from variants: B.C. study

Study is not peer-reviewed but looks at infections during B.C.’s spring wave

A new preprint study released by B.C. researchers suggests that a single dose of an mRNA COVID-19 vaccine reduced the risk of infection in seniors by two-thirds during B.C.’s third wave in the spring.

The study from B.C. Centre for Disease Control researchers, which has not yet been peer-reviewed, looked at the effectiveness of B.C.’s vaccination plan, which involved delaying the second dose in order to get a first shot out to more people. The gap between first and second doses in B.C. began at 16 weeks but has recently shrunk down to eight.

The study looked at 16,993 people, of whom seven per cent tested positive for COVID and 93 per cent tested negative. Samples were collected from seniors age 70 and up who lived in the community and received their first dose of a mRNA vaccine at least 21 days earlier. The collection period started on April 4 and ended on May 1.

According to the study, vaccine effectiveness was “negligible” at 14 per cent between zero and 13 days after the first dose. Between 14 and 21 days post-shot, effectiveness rose to 43 per cent and by 35 to 41 days, it increased sharply to 75 per cent. On average, effectiveness was at 65 per cent overall at any period between 21 and 45 days.

The study found that effectiveness did shrink for variants of concern; 21 or more days post shot, vaccines had an effectiveness of 72 per cent against non-variant COVID, 67 per cent for B.1.1.7 (alpha, U.K. origin) and 61 per cent for P1 (gamma, Brazil origin).

About 45 per cent of the COVID-positive samples collected were of B.1.1.7 (alpha, U.K. origin), 28 per cent were P1 (gamma, Brazil origin) and 24 per cent were non-variant of concern. The study did not look at the delta (B.1.617) variant.

READ MORE: Rate of more contagious delta COVID-19 variant increasing in B.C. with 500 cases so far


@katslepian

katya.slepian@bpdigital.ca

Like us on Facebook and follow us on Twitter.

Coronavirusvaccines

Just Posted

Brodie Stuart and her mom, Mikel Stuart, gather for the celebration at Parkview Elementary on June 18, 2021. (Zachary Roman - Eagle Valley News)
Three Shuswap parents honoured for combined 34 years of volunteering

Parkview Elementary parent advisory council members surprised by appreciative flash mob

Fruit farmers in the Okanagan and Creston valleys are in desperate need of cherry harvesters amid COVID-19 work shortages. (Photo: Unsplash/Abigail Miller)
‘Desperate’ need for workers at Okanagan cherry farms

Fruit farmers are worried they’ll have to abandon crops due to COVID-19 work shortages

Centennial Field in Blind Bay will be the site of Market by the Bay on Thursday nights starting June 24, 2021. (Columbia Shuswap Regional District photo)
Forty vendors expected for new Market by the Bay in the South Shuswap

Market starting June 24 to be situated at Centennial Field in Blind Bay

A GoFundMe campaign has been launched to collect donations ahead of Kristy Handel’s 33-kilometre run for Chelaine McInroy (pictured) to cover costs for a new prosthetic leg after her June 12, 2021, surgery. (GoFundMe)
Salmon Arm woman runs to raise funds for friend’s new prosthetic leg

33-kilometre Run for Chelaine to help athlete cover medical costs from latest surgery

A tent housing a mobile vaccination clinic. (Interior Health/Contributed)
Over 5K jabbed at Interior Health mobile COVID-19 vaccine clinics

The clinics have made stops in more than 40 communities since launching last week

A small pod of Pacific white-sided dolphins pass by close to shore in Campbell River June 16, 2021. Still capture from video courtesy of Kimberly Hart
VIDEO: Dolphin sunset captured from Vancouver Island shore

Spectacular setting for view of travelling pod of Pacific white-sided dolphins

Earls On Top at 211 Bernard Avenue in Kelowna. (Google Maps photo)
Downtown Kelowna’s Earls ordered closed after COVID-19 transmission

Earls on Top on Bernard Avenue will be closed from June 18 to June 27

A motorycle crash has been reported on Westside Road. (Google Maps)
UPDATE: Westside Road reopened following motorcycle crash near Vernon

AIM Roads advises drivers to expect delays due to congestion

(File photo)
Penticton not holding Canada Day activities out of respect for Indigenous people

Cities across B.C. are cancelling the holiday after an increased spotlight on Canada’s dark history

Dereck Donald Sears. (Contributed/Crimestoppers)
Murder charge laid in relation to suspicious Kelowna death

Dereck Donald Sears is charged with second-degree murder in the death of Darren Middleton

Police are asking for public assistance in locating Anthony Graham who has been charged with the murders of Kamloops brothers Carlo and Erick Fryer. (RCMP photo)
2 charged, suspect at large in killings of B.C. brothers linked to gang activity: RCMP

Kamloops brothers Erick and Carlo Fryer were found deceased in May on a remote Okanagan road

Albert Health Minister Tyler Shandro and Alberta Premier Jason Kenney unveil an opening sign after speaking about the Open for Summer Plan and next steps in the COVID-19 vaccine rollout, in Edmonton, Friday, June 18, 2021. THE CANADIAN PRESS/Jason Franson
Alberta 1st province in Canada to lift all COVID-19 public health restrictions

70.2% of eligible citizens 12 and older in the province have received a dose of the vaccine

Fraser Health registered nurse Ramn Manan draws a dose of the Pfizer COVID-19 vaccine into a syringe at a walk-up vaccination clinic at Bear Creek Park, in Surrey, B.C., on Monday, May 17, 2021. THE CANADIAN PRESS/Darryl Dyck
‘Honour our fathers’ with COVID-19 vaccine protection, B.C. urges

109 new cases Friday, 75 per cent of 12 and up immunized

Most Read