A health care worker prepares a dose of the Pfizer-BioNTech COVID-19 vaccine, in Los Angeles, Calif., on Jan. 7, 2021.LUCY NICHOLSON/Reuters
Pfizer Inc and BioNTech said on Thursday their vaccine is around 91 per cent effective at preventing COVID-19, citing updated trial data that included participants inoculated for up to six months.
The shot also showed early signs of preventing disease in a small subset of study volunteers in South Africa, where a concerning new variant called B.1.351 is circulating.
Although lower than the stunning 95 per cent efficacy result reported from its 44,000-person clinical trial in November, overall efficacy of 91.3 per cent shows the vaccine to be a powerful tool against an evolving virus. The virus now has more transmissible forms and those that have been shown to evade antibody protection in lab studies and real-world clinical trials.
“These data reinforce our view that we have some really potent vaccines,” said Danny Altmann, a professor of immunology at Britain’s Imperial College London, who was not involved in the Pfizer trial.
Pfizer’s Chief Executive Officer Albert Bourla said the updated result, which includes data on more than 12,000 people fully inoculated for at least six months, positions the drugmakers to submit for full U.S. regulatory approval.
Canada pre-purchased millions of doses of seven different vaccine types, and Health Canada has approved four so far for the various provincial and territorial rollouts. All the drugs are fully effective in preventing serious illness and death, though some may do more than others to stop any symptomatic illness at all (which is where the efficacy rates cited below come in).
- Also known as: Comirnaty
- Approved on: Dec. 9, 2020
- Efficacy rate: 95 per cent with both doses in patients 16 and older, and 100 per cent in 12- to 15-year-olds
- Traits: Must be stored at -70 C, requiring specialized ultracold freezers. It is a new type of mRNA-based vaccine that gives the body a sample of the virus’s DNA to teach immune systems how to fight it. Health Canada has authorized it for use in people as young as 12.
- Also known as: SpikeVax
- Approved on: Dec. 23, 2020
- Efficacy rate: 94 per cent with both doses in patients 18 and older, and 100 per cent in 12- to 17-year-olds
- Traits: Like Pfizer’s vaccine, this one is mRNA-based, but it can be stored at -20 C. It’s approved for use in Canada for ages 12 and up.
- Also known as: Vaxzevria
- Approved on: Feb. 26, 2021
- Efficacy rate: 62 per cent two weeks after the second dose
- Traits: This comes in two versions approved for Canadian use, the kind made in Europe and the same drug made by a different process in India (where it is called Covishield). The National Advisory Committee on Immunization’s latest guidance is that its okay for people 30 and older to get it if they can’t or don’t want to wait for an mRNA vaccine, but to guard against the risk of a rare blood-clotting disorder, all provinces have stopped giving first doses of AstraZeneca.
- Also known as: Janssen
- Approved on: March 5, 2021
- Efficacy rate: 66 per cent two weeks after the single dose
- Traits: Unlike the other vaccines, this one comes in a single injection. NACI says it should be offered to Canadians 30 and older, but Health Canada paused distribution of the drug for now as it investigates inspection concerns at a Maryland facility where the active ingredient was made.
How many vaccine doses do I get?
All vaccines except Johnson & Johnson’s require two doses, though even for double-dose drugs, research suggests the first shots may give fairly strong protection. This has led health agencies to focus on getting first shots to as many people as possible, then delaying boosters by up to four months. To see how many doses your province or territory has administered so far, check our vaccine tracker for the latest numbers.
The vaccine is currently authorized on an emergency basis by the U.S. Food and Drug Administration.
The trial data “provide the first clinical results that a vaccine can effectively protect against currently circulating variants, a critical factor to reach herd immunity and end this pandemic for the global population,” Ugur Sahin, chief executive officer at BioNTech, said in a statement.
Experts fear new variants of COVID-19 from South Africa and Brazil may be resistant to existing vaccines and treatment. More than 300 cases of the South African variant have been detected in more than 25 U.S. states and jurisdictions, according to federal data.
Lab tests have previously indicated that the Pfizer/BioNTech vaccine was less potent but still offered a robust defence against the B.1.351 variant that first emerged in South Africa.
The data released on Thursday offered the first look at how the vaccine might work in people against the South African variant. Among a group of 800 study volunteers in South Africa, where the variant is widespread, there were nine cases of COVID-19, all of which occurred among participants who got the placebo. Of those nine cases, six were among individuals infected with the South African variant.
“The Pfizer data are a big deal,” said Shane Crotty, a virologist at the La Jolla Institute for Immunology in San Diego, noting that the results offer the first data in humans about how so-called mRNA vaccines such as Pfizer’s will perform against the South African variant.
“Six infections versus zero is something,” he said in an e-mail, but noted the sample size is still “not enough to make conclusions about protection.”
Although the B.1.1.7 variant that originated in Britain has quickly spread across Europe and is gaining a foothold in the United States, the B.1.351 variant and similar variants are more concerning because they have shown to reduce the efficacy of three different COVID-19 vaccines in clinical trials in South Africa.
BioNTech reiterated this week there would likely be a future need for booster shots that specifically address new variants and that the group was preparing to upgrade its vaccine when needed. A spokeswoman said on Thursday its strategy remains in place.
The vaccine was 95.3 per cent effective in preventing severe disease as defined by the U.S. Food and Drug Administration.
There were also no serious safety concerns observed in trial participants up to six months after the second dose, the companies said.
The trial reviewed more than 900 confirmed cases of COVID-19, most of which were among participants who received a placebo.
The results follow separate data that showed the vaccine is safe and effective in 12– to 15-year olds, paving the way for the drugmakers to seek U.S. and European approvals for this group.
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