AstraZeneca says late-stage trials of its COVID-19 vaccine were 'highly effective' in preventing disease

AstraZeneca said Monday that late-stage trials showed that its COVID-19 vaccine with Oxford University was up to 90 per cent effective in preventing disease. The vaccine is one of several that Canada has preordered.

The results are based on interim analysis of trials in the U.K. and Brazil of a vaccine developed by Oxford University and manufactured by AstraZeneca. No hospitalizations or severe cases of COVID-19 were reported in those receiving the vaccine, AstraZeneca said.

The trial looked at two different dosing regimens. A half dose of the vaccine followed by a full dose at least one month apart was 90 per cent effective. A second regimen using two full doses one month apart was 62 per cent effective. The combined results showed an average efficacy rate of 70 per cent.

"These findings show that we have an effective vaccine that will save many lives," Prof. Andrew Pollard, chief investigator for the trial, said in a statement. "Excitingly, we've found that one of our dosing regimens may be around 90 per cent effective."

AstraZeneca is the third major drug company to report late-stage results for its potential COVID-19 vaccine as public health officials around the world anxiously wait for vaccines that will end the pandemic that has killed almost 1.4 million people. Pfizer/BioNTech and Moderna last week reported preliminary results from late-stage trials showing their vaccines were almost 95 per cent effective.

While the AstraZeneca vaccine can be stored between 2 C and 8 C, the Pfizer and Moderna products must be stored at freezer temperatures. In Pfizer's case, it must be kept at the ultra-cold temperature of around –70 C.

WATCH | AstraZeneca says late-stage trials of COVID-19 vaccine were 'highly effective'

Trials show AstraZeneca COVID-19 vaccine ‘highly effective’

4 years ago

Duration 4:04

British drugmaker AstraZeneca has said the COVID-19 vaccine it’s developed with the University of Oxford is 70 per cent effective on average. The vaccine is one of several that Canada has already preordered and is considered more globally accessible.

The AstraZeneca vaccine is also cheaper. 

The results come as COVID-19 infection rates are rising in most U.S. states and in many countries, including Canada, amid a resurgence of the virus, which is once again prompting governments to shut down businesses and restrict social gatherings around the world. England is still in the middle of a four-week lockdown that has closed all non-essential shops, while in the U.S., the government's top health agency has recommended that Americans not travel to visit family and friends over the Thanksgiving holiday this week.

AstraZeneca said it will immediately apply for early approval of the vaccine where possible, and it will seek an emergency use listing from the World Health Organization so it can make the vaccine available in low-income countries.

The vaccine uses a weakened version of a common cold virus that is combined with genetic material for the characteristic spike protein of the virus that causes COVID-19. After vaccination, the spike protein primes the immune system to attack the virus if it later infects the body.

Smaller dose may reduce costs

Peter Openshaw, professor of experimental medicine at Imperial College London, said the finding that a smaller initial dose is more effective than a larger one is good news because it may reduce costs and mean more people can be vaccinated.

"The report that an initial half-dose is better than a full dose seems counterintuitive for those of us thinking of vaccines as normal drugs. With drugs, we expect that higher doses have bigger effects, and more side-effects," he said. "But the immune system does not work like that."

WATCH | Who would get a COVID-19 vaccine first and when?

Cost, efficacy, logistics factor into vaccine rollout, epidemiologist says

4 years ago

Duration 5:41

With several COVID-19 vaccines in development around the world, cost and efficacy are important. However, logistical considerations may be the deciding factor in what becomes available across Canada, according to epidemiologist Dr. Christopher Labos.

Dr. Christopher Labos, a cardiologist in Montreal trained in epidemiology, said vaccines do not have to be perfect or prevent every case of COVID-19.

"The point is to drastically reduce the caseload, to drastically reduce the number of new infections so that we don't have these outbreaks, so we don't have the hospital systems overwhelmed," Labos said Monday on CBC News Network. 

"That's the main take-home message from a lot of these vaccines. Not only do they prevent cases but they seem to prevent serious cases of COVID-19."

Labos said he suspects because the Pfizer/BioNTech and Moderna vaccines need to be stored at low temperatures, they are probably going to be reserved for institutions, while the Oxford/AstraZeneca one might be rolled out in the community. 

Dr. Anand Kumar, an infectious disease expert and intensive care unit physician in Winnipeg, said AstraZeneca used a proven vaccine technology.

"We have months where we could still have horrendous mortality rates," Kumar said. "It's good news, but it's down the road and we really need to keep the virus under control "

The results reported Monday come from trials in the U.K. and Brazil that involved 23,000 people. Late-stage trials are also underway in the U.S., Japan, Russia, South Africa, Kenya and Latin America, with further trials planned for other European and Asian countries.

AstraZeneca reported two pauses in the Phase 3 clinical trial of its vaccine candidate, AZD1222. "No serious safety events related to the vaccine have been confirmed," the company said in a release. 

AstraZeneca has been ramping up manufacturing capacity, so it can supply hundreds of millions of doses of the vaccine starting in January, chief executive Pascal Soriot said earlier this month.

Soriot said Monday that the Oxford vaccine's simpler supply chain and AstraZeneca's commitment to provide it on a non-profit basis during the pandemic mean it will be affordable and available to people around the world.

"This vaccine's efficacy and safety confirm that it will be highly effective against COVID-19 and will have an immediate impact on this public health emergency," Soriot said.

Now that AstraZeneca has released its interim results, regulators must approve the vaccine before it can be widely distributed.

Britain has ordered 100 million doses of the Oxford vaccine, and the government says several million doses can be produced before the end of the year if it gains approval from the regulator. Canada has ordered 20 million doses, enough for 10 million people.

British Health Secretary Matt Hancock said he felt "a great sense of relief" at the news of the AstraZeneca vaccine's effectiveness.

He said just months ago, as the virus raged, "the idea that by November we would have three vaccines, all of which have got high effectiveness, I would have given my eye teeth for."