Oxford COVID-19 Vaccine Shows Promise in Early Trial Results

Oxford COVID-19 Vaccine Shows Promise in Early Trial Results

The experimental vaccine triggered an immune response to SARS-CoV-2 and appeared to be safe. Find out what happens next.

Updated on July 21, 2020 at 9:00am EST.

There are more than 160 experimental COVID-19 vaccines in development around the world but one of them, in particular, has become a leading contender in the global race to halt the spread of the coronavirus that causes the disease—SARS-CoV-2.

A COVID-19 vaccine called AZD1222 being developed by AstraZeneca and the University of Oxford triggered “robust immune responses” among participants in early-stage clinical trials. The highly anticipated findings, which were published on July 20 in The Lancet, revealed that the vaccine triggered an increase in antibodies (proteins in the blood that help fight off infection) and a T-cell response. T-Cells also help the body fight disease.

The randomized Phase I/II trial included 1,077 healthy adults between the ages of 18 and 55. The scientists gave the experimental COVID-19 vaccine to 543 people. Of these, 533 received a single dose and 10 received two doses of AZD1222 one month apart.

The effectiveness of the experimental vaccine was assessed against a meningococcal conjugate vaccine that served as a control. Only the researchers knew which treatment the participants received.

The trials showed that neutralizing antibody responses were detected in 91 percent of the participants studied who received a single dose of AZD1222 and 100 percent of the participants who received the booster dose. A T-cell response was also induced in all of the participants studied, which was maintained two months after injection.

Many effective vaccines trigger both an antibody and a T-cell response.

How the vaccine works
The Oxford vaccine uses another type of harmless virus to deliver biological instructions for how to fight off the coronavirus that causes COVID-19.

The viral vector used in the vaccine is based on a weakened version of a common cold virus (adenovirus) that causes infections in chimpanzees and contains the genetic material of the SARS-CoV-2 virus spike protein—the protein the coronavirus uses to invade people’s cells.

Recombinant vector vaccines, such as AZD1222, act like a natural infection, which means they may be particularly effective in teaching the immune system how to fight germs. After vaccination, the surface spike protein is produced, which primes the immune system to attack COVID-19 if it ever infects the body.

Is it safe?
The virus that causes the common cold in chimpanzees was genetically modified to make it “appear” more like SARS-CoV-2—but it can’t cause infections in people.

The early trial results showed that AZD1222 has only minor to moderate side effects, including pain, feeling feverish, chills, muscle ache, headache and malaise. These effects, however, were eased among participants who received acetaminophen to prevent them from occurring.

No serious negative reactions were reported.

The next steps
Though these early trial results are promising and show that the vaccine induced a reaction in the body, much larger Phase III trials are still needed to determine if AZD1222 actually provides immunity to COVID-19.

Phase III trials are already underway in the U.K., the United States, Brazil and South Africa. 

AstraZeneca announced, meanwhile, that it has already concluded agreements for at least 400 million doses of AZD1222 and has the capacity to manufacture one billion doses. The company says it hopes to begin first deliveries by the end of 2020.

Back on May 21, the United States announced it secured 300 million doses of the experimental vaccine—nearly one-third of the first one billion doses the drug maker plans to produce.

The U.S. Department of Health and Human Services secured the vaccines by pledging up to $1.2 billion to accelerate the drug maker’s vaccine development program.

Medically reviewed in July 2020.

The New York Times. “Coronavirus Vaccine Tracker.”
Pedro M Folegatti, MSc; Katie J Ewer, PhD; Parvinder K Aley, PhD, et al. “Safety and immunogenicity of the ChAdOx1 nCoV-19 vaccine against SARS-CoV-2: a preliminary report of a phase 1/2, single-blind, randomised controlled trial.” The Lancet. July 2020.
AstraZeneca. “COVID-19 vaccine AZD1222 showed robust immune responses in all participants in Phase I/II trial.”
World Health Organization. “Vaccine Immunology.”
AstraZeneca. “AstraZeneca advances response to global COVID-19 challenge as it receives first commitments for Oxford’s potential new vaccine.”
Oxford University. “Trial of Oxford COVID-19 vaccine starts in Brazil.”
AstraZeneca. “AstraZeneca to supply Europe with up to 400 million doses of Oxford University’s vaccine at no profit.”
U.S. Department of Health and Human Services. “Trump Administration’s Operation Warp Speed Accelerates AstraZeneca COVID-19 Vaccine to be Available Beginning in October.”

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