Potential COVID-19 vaccine clears 'major milestone': Sask

Henrietta Brewer
May 26, 2020

A research team based out of China has reported success rates in a newly developed vaccine which has reached the human clinical trial phase as of right now. The news comes soon after the Oxford vaccine trial, which was a strong contender in the vaccine development phase showcased some negative results. The first-in-human trial showed that the Ad5 vectored Covid-19 vaccine was tolerable and immunogenic in healthy adults.

In the majority of volunteers, they said the vaccine also stimulated a rapid T cell response. Specific T-cell response peaked at day 14 post-vaccination.

Authors noted, "However, both the antibody and T-cell response could be reduced by high pre-existing immunity to adenovirus type 5 (the common cold virus vector/carrier)-in the study, 44%-56% of participants in the trial had high pre-existing immunity to adenovirus type 5 and had a less positive antibody and T-cell response to the vaccine". Speaking to STATNews, Michael Mina from Harvard's T.H. Chan School of Public Health, says this is a common problem with vaccines using this kind of adenovirus delivery system.


"If you already have seen a virus or have some pre-existing immunity to it ... you run the risk of having your immune response get skewed and picking up primarily the thing you're already immune to or that you've already seen and not focusing so much on the new aspect, which in this case would be the coronavirus proteins that were placed onto the adenovirus vector", says Mina. The open-label trial in these individuals shows promising results after 28 days, yet the final results will take six months.

"The challenges in the development of a COVID-19 vaccine are unprecedented, and the ability to trigger these immune responses does not necessarily indicate that the vaccine will protect humans from COVID-19", Chen explained. Other vaccine candidates have reported better results in the levels of neutralizing antibodies.

Prime Minister Justin Trudeau announced $1.1 billion in federal funding for COVID-19 vaccine research on April 23.


Del Rio, a professor of medicine at Emory University, is one of the researchers testing the efficacy of a vaccine at the Atlanta college's Vaccine and Treatment Evaluation Unit developed by the MA biotech firm Moderna in cooperation with the National Institutes of Health.

A much-anticipated COVID-19 vaccine trial in the United Kingdom has only a 50 percent chance at success, down from earlier estimates of 80 percent, the professor co-leading the development of the vaccine told a British newspaper.

"It's a race against the virus disappearing, and against time", Hill recently said.


"What we hope is that there will be not one vaccine but several vaccines that will be approved", Barouch said. But at the moment, there's a 50% chance that we get no result at all.

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