Single dose of Pfizer or Moderna enough to prevent COVID-19 infection in two-thirds of cases, new B.C. study finds
A new study from the B.C. Centre for Disease Control found that a single shot of Pfizer or Moderna COVID-19 vaccines reduced the risk of infection in British Columbians 70 and older by about two-thirds.
The study, which was posted this week on the BCCDC website, and has not yet been peer reviewed, also found that protection was only slightly reduced when it came to two variants of concern, the alpha variant (also known as the B.1.1.7 and associated with the U.K.) and the gamma variant (or P.1, associated with Brazil).
“This is wonderful news and especially meaningful because this was protection that was provided during the peak of pandemic risk,” said Dr. Danuta Skowronski, the study’s lead author.
Skowronski, the BCCDC’s epidemiology lead of influenza and emerging respiratory pathogens, added that she was “thrilled” and “energized” by the findings, which she said likely underestimated the protection warded by a first dose.
The BCCDC collected 16,993 specimens from adults 70 and older living in the community in British Columbia, rather than in long-term care.
Researchers collected the samples during the peak of the spring 2021 wave, between April 1 and May 14.
“Such protection is particularly meaningful considering that it was provided during a period of peak pandemic risk, when (variants of concern) were predominantly contributing to the epidemic in BC,” wrote the study’s author, Dr. Danuta Skowronski.
Researchers found vaccine effectiveness was negligible for the first two weeks after a shot.
Effectiveness increased to 43 per cent during week three, and to 75 per cent during week five, the study said.
Overall vaccine effectiveness three weeks after the first dose was 72 per cent for non-variants of concern, 67 per cent for the alpha variant, and 61 per cent for the gamma variant.
Skowronski pointed out that this appears to be the first study globally that broke out vaccine effectiveness on the gamma variant and said she was “heartened” by all the results.
Researchers did not examine the question of how long protection from a single dose of mRNA vaccine against COVID-19 infection might last.
That work is ongoing, Skowronski added, as large numbers of British Columbians begin to receive their second doses.
“Will there be a new variant? Will the vaccines be very effective over time? And those are the things that keep me up at night,” said the BCCDC’s medical director, Mel Krajden.
Skowronski added the research will also help determine whether British Columbians will need a third, booster dose at some point.
But she pointed out the fact the province extended the gap between the first and second doses, originally up to four months, could have an intended positive benefit of “higher boost responses.”
“It’s not a done deal that we’re going to need a third, booster dose,” she said.
CTVNews.ca Top Stories
'I just can't believe that it took so long': Body found in wreckage 3 months after deadly fire
A man accused of arson in a January Old Strathcona apartment fire is expected to be charged with manslaughter after a body was discovered in the burned building late last month.
No proof man lied to brother about number of kittens born in litter, B.C. tribunal rules
A man was denied a $5,000 payout from his brother after a B.C. tribunal dismissed his claim disputing how many kittens were born in a litter.
Snakes almost on a plane: U.S. TSA discovers a bag with small snakes in passenger's pants
According to an X post by the Transportation Security Administration, officers at the Miami International Airport found the small bag of snakes hidden in a passenger's trousers on April 26 at a checkpoint.
Russia puts Ukrainian President Zelenskyy on its wanted list
Russia has put Ukrainian President Volodymyr Zelenskyy on its wanted list, Russian state media reported Saturday, citing the interior ministry’s database.
The pros and cons of discussing mental health issues in the workplace
A group of lawyers has written what they call a groundbreaking book about how mental health is perceived in the legal profession.
A candidate for Germany's key party was beaten up while campaigning for European elections
A candidate for Chancellor Olaf Scholz's center-left party in next month's election for the European Parliament was beaten up and seriously injured while campaigning in an eastern city, the party said Saturday.
Explosion at train station leads to discovery of stolen car on Montreal's South Shore: police
Police are investigating after a BMW exploded in the St-Lambert Exo train station parking lot on Montreal's South Shore.
A Chinese driver is praised for helping reduce casualties in a highway collapse that killed 48
A Chinese truck driver was praised in local media Saturday for parking his vehicle across a highway and preventing more cars from tumbling down a slope after a section of the road in the country's mountainous south collapsed and killed at least 48 people.
Two killed after collision with truck on Hwy. 417 near Limoges, Ont.
Ontario Provincial Police say two people were killed after a car and a transport truck collided in the westbound lanes of Highway 417 near Limoges, Ont. on Tuesday afternoon.