The study, released Monday by scientists at the University of Edinburgh and the University of Strathclyde, examined hospitalization rates among more than 1.1 million Scots who received one shot of either vaccine between Dec. 8 and Feb. 15.
The researchers examined the effectiveness of the vaccines after one week, two weeks, three weeks, four weeks and longer. The highest protection came after four weeks. The Pfizer-BioNTech vaccine lowered the risk of hospitalization by 85 per cent while the Oxford-AstraZeneca jab reduced it by 94 per cent.
“We are over all very, very impressed with both these vaccines. Both are performing incredibly well,” said Aziz Sheikh, professor of primary care research and development at the University of Edinburgh. “We now have national evidence, across an entire country, that vaccination provides protection against COVID-19 hospitalizations.”
Jim McMenamin, a director at Public Health Scotland, said the results were particularly welcomed because they showed effectiveness against the British variant of the virus, which is more contagious and deadlier than the original version. The mutation was first detected in November and now accounts for more than 80 per cent of all cases in Scotland and elsewhere in the U.K. “Certainly for the U.K. variant that we have seen across the time period of the study, this is a very encouraging vaccine effect,” Dr. McMenamin said.
COVID-19 is caused by a virus called SARS-CoV-2, and as it spread around the world, it mutated into new forms that are more quickly and easily transmitted through small water droplets in the air. Canadian health officials are most worried about variants that can slip past human immune systems because of a different shape in the spiky protein that latches onto our cells. The bigger fear is that future mutations could be vaccine-resistant, which would make it necessary to tweak existing drugs or develop a new “multivalent” vaccine that works against many types, which could take months or years.
Not all variants are considered equal threats: Only those proven to be more contagious or resistant to physical-distancing measures are considered by the World Health Organization to be “variants of concern.” Five of these been found in Canada so far. The WHO refers to them by a sequence of letters and numbers known as Pango nomenclature, but in May of 2021, it also assigned them Greek letters that experts felt would be easier to remember.
- Country of origin: Britain
- Traits: Pfizer-BioNTech and Moderna vaccines are still mostly effective against it, studies suggest, but for full protection, the booster is essential: With only a first dose, the effectiveness is only about 66 per cent.
- Spread in Canada: First detected in Ontario’s Durham Region in December. It is now Canada’s most common variant type. Every province has had at least one case; Ontario, Quebec and the western provinces have had thousands.
- Country of origin: South Africa
- Traits: Some vaccines (including Pfizer’s and Oxford-AstraZeneca’s) appear to be less effective but researchers are still trying to learn more and make sure future versions of their drugs can be modified to fight it.
- Spread in Canada: First case recorded in Mississauga in February. All but a few provinces have had at least one case, but nowhere near as many as B.1.1.7.
- Country of origin: Brazil
- Traits: Potentially able to reinfect people who’ve recovered from COVID-19.
- Spread in Canada: B.C. has had hundreds of cases, the largest known concentration of P.1 outside Brazil. More outbreaks have been detected in Ontario and the Prairies.
DELTA (B.1.617 AND B.1.617.2)
- Country of origin: India
- Traits: Spreads more easily. Single-dosed people are less protected against it than those with both vaccine doses.
- Spread in Canada: All but a few provinces have recorded cases, but B.C.’s total has been the largest so far.
- Country of origin: Peru
- Traits: Spreads more easily. Health officials had been monitoring it since last August, but the WHO only designated it a variant of concern in June of 2021.
- Spread in Canada: A handful of travel-related cases were first detected in early July.
If I’m sick, how do I know whether I have a variant?
Health officials need to genetically sequence test samples to see whether it’s the regular virus or a variant, and not everyone’s sample will get screened. It’s safe to assume that, whatever the official variant tallies are in your province, the real numbers are higher. But for your purposes, it doesn’t matter whether you contract a variant or not: Act as though you’re highly contagious, and that you have been since before your symptoms appeared (remember, COVID-19 can be spread asymptomatically). Self-isolate for two weeks. If you have the COVID Alert app, use it to report your test result so others who may have been exposed to you will know to take precautions.
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The findings could also ease some fears about the effectiveness of the Oxford-AstraZeneca vaccine in older people.
There have been concerns that the vaccine provides less protection for people over the age of 65 and several countries, including France, Germany and Sweden, have advised that it should only be used in people under that age. There were insufficient data in clinical trials to assess the vaccine’s effectiveness in older age groups, but medical regulators in Britain, the European Union and the World Health Organization have approved its use for all adults.
In Scotland, the Oxford-AstraZeneca vaccine has been used primarily for people over the age of 65 and the study’s findings indicated that it was just as effective in preventing hospitalization. Among the over 80s, the study found an overall 81-per-cent reduction in the numbers admitted to hospital. “From the data that we’ve got at the moment, it seems like this vaccine seems to be working across age groups,” Dr. Sheikh said.
The study did not offer any findings on whether people who have been vaccinated can still pass on the virus. “I think it’s really important to emphasize that these data don’t support any comment about transmission or indeed transmission policy and therefore we wouldn’t be advising on the basis of these results that we should alter anything that we’ve got implemented currently to stop transmission of the virus from person to person within Scotland,” said Josie Murray, a consultant epidemiologist at Public Health Scotland.
There was also no indication as to how long the vaccine protection will last. Both vaccine makers have recommend that people receive a second dose around 28 days after their first shot. However, Britain has delayed the booster shot up to 12 weeks in order to vaccinate more people. The study only looked at efficacy at between 28 and 34 days. The scientists plan to do more research to assess longer-term protection.
The Globe and Mail
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