Story at a glance

  • Two groups developing vaccines published their results from phase 1 and 2 clinical trials.
  • A vaccine candidate from a group of researchers at Oxford University seems to provoke immune responses through T cells and antibodies.
  • Both groups are moving into Phase 3 clinical trials.

On Monday, the medical journal The Lancet published two studies about two promising vaccine candidates. The Oxford University group based at Jenner Institute tested their vaccine on more than 1,000 people. A biotech group in China called CanSino tested their vaccine on about 500 participants.

The researchers behind the Oxford-AstraZeneca vaccine candidate, called AZD1222, previously published press releases about their preliminary results. The Lancet paper presents the data from the combined Phase 1/2 clinical trial of the vaccine. The vaccine candidate “provoked a T-cell response within 14 days of vaccination” and “an antibody response within 28 days,” states a press release from Oxford University.

These are two different types of immune responses, which some are unofficially calling dual immune response or dual immune action. T cells are the white blood cells which can identify and remember pathogens that they’ve encountered before. Antibodies are proteins that can attach to foreign particles. Neutralizing antibodies are antibodies that attach to a pathogen in a place that prevents it from entering cells.

The Oxford group recruited participants between the ages of 18 and 55 who didn’t have a history of SARS-CoV-2 infection and no symptoms related to COVID-19; the median age of trial participants was 35. They all received the same dosage as an injection. Only 10 people got a booster shot of the vaccine 28 days after the first dose. Some of the side effects in participants of the clinical trial included fever, chills, headaches and muscle pain.

Because there was a T-cell response, this could potentially mean long term immunity. “We hope this means the immune system will remember the virus, so that our vaccine will protect people for an extended period,” says Andrew Pollard, Chief investigator of the Oxford Vaccine Trial at Oxford University, according to the press release. “However, we need more research before we can confirm the vaccine effectively protects against SARS-CoV-2 infection, and for how long any protection lasts.”


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"I’d want to see, in a Phase 2 trial, two doses consistently inducing a neutralizing antibody response, and that it’s relatively long-lived — not months, not a few weeks,” says Paul Offit, who is director of the Vaccine Education Center at Children’s Hospital of Philadelphia and was not involved with the study, to The Washington Post.

In the other vaccine study published in The Lancet, CanSino found that their vaccine candidate did induce an immune response in the form of neutralizing antibodies, but it didn’t work as well in people aged 55 and older.

Unlike CanSino, the Oxford group did not test their vaccine on people older than 55, so there is no data on how that vaccine would perform in older age groups. Although there may be safety concerns for giving a vaccine to older people, the study included 65 participants older than 55 years old. “Since elderly individuals face a high risk of serious illness and even death associated with COVID-19 infection, they are an important target population for a COVID-19 vaccine," says Wei Chen, one of the coauthors in the CanSino study and based at the Beijing Institute of Biotechnology, in a statement according to CNN.

The group also found a T-cell response in 88 percent of participants who got their vaccine. They report similar side effects like fever, headache and fatigue. "It is possible that an additional dose may be needed in order to induce a stronger immune response in the elderly population, but further research is underway to evaluate this,” says Chen. The CanSino vaccine candidate is already approved for emergency use for the country’s military.

The Oxford group will move forward with this vaccine candidate to the last phase, Phase 3 clinical trials. “These encouraging results support further evaluation of this candidate vaccine in our ongoing large scale Phase III programme, that is still needed to assess the ability of the vaccine to protect people from COVID-19,” says Sarah Gilbert, Professor of Vaccinology at the University of Oxford Jenner Institute and co-author of the study, in the press release.


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The researchers testing the Oxford-AstraZeneca vaccine candidate say that in future trials they will give patients two doses instead of one. “We saw the strongest immune response in the 10 participants who received two doses of the vaccine,” says Pollard.

Phase 3 clinical trials for vaccine development is the biggest trial yet. They will need to test the vaccine candidate in thousands of patients and collect more data on the vaccine’s efficacy and safety. CanSino will also move forward with Phase 3 trials for its vaccine candidate.

An editorial published in The Lancet by Naor Bar-Zeev and William Moss of the Johns Hopkins Bloomberg School of Public Health alongside the studies says that these results are “encouraging,” but “when things are urgent, we must proceed cautiously.” It’s also important to keep in mind that experts do not know yet what level of immune response will be protective against infection or prevent severe cases of COVID-19. That’s something that requires more research and understanding on how our bodies react to the virus.

While it’s incredible that two promising vaccine candidates have moved through Phase 1 and 2 of clinical trials this quickly, it’s not necessarily a sign that we will have a viable vaccine shortly. Bar-Zeev and Moss write, “Equitable distribution of future COVID-19 vaccines also requires detailed evaluation of local country needs and priorities, community engagement, and trust.”

For up-to-date information about COVID-19, check the websites of the Centers for Disease Control and Prevention and the World Health Organization. For updated global case counts, check this page maintained by Johns Hopkins University.

You can follow Chia-Yi Hou on Twitter.


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Published on Jul 21, 2020