What the latest positive news on a leading Covid-19 vaccine candidate means

  • Clinical trials normally include a few phases.
  • The next phase of this trial is already on the go globally.
  • Supply deals are already in place should the green light be given.

AstraZeneca's experimental Covid-19 vaccine was safe and produced an immune response in early-stage clinical trials in healthy volunteers, according to a study published in a top journal on Monday.

The vaccine, called AZD1222, and being developed by global biopharmaceutical company AstraZeneca and scientists at Britain's University of Oxford, did not show any serious side-effects and produced sufficient antibody and T-cell immune responses, according to trial results published in The Lancet medical journal.

But what lies ahead before this vaccine can be mass-produced and distributed?

The trial results

The researchers performed a phase 1/2 single-blind randomised controlled trial in five trial sites around the UK.

The vaccine was developed from a chimpanzee adenovirus-vectored vaccine, which was combined with a spike protein from SARS-Cov-2 – this means that the adenovirus, a milder virus that causes nothing more serious than a common cold, was "fed" with genetic instructions to help the trick the body in creating antibodies against SARS-Cov-2, the coronavirus that is currently causing Covid-19.

During the clinical trial, 1 077 healthy adults between the ages of 18 and 55, with no previous infection with Covid-19, were randomly assigned to receive the vaccine at a determined dosage between 23 April and 21 May 2020. They were then divided into various groups (referred to as subsets): Some received only one dose, while other received two doses.

The researchers found no serious side-effects from the vaccine.

A sufficient antibody response occurred in the subset of 32 out of 35 participants after one dose, and all participants showed neutralising antibody activity after the booster shot was administered.

Where participants did experience slight pain and fever from the vaccine, these mild side-effects were successfully treated with paracetamol.

Clinical trial phases – a recap

While the results published on Monday are promising, it's important to understand how clinical trials work.

Clinical trials in vaccine development usually consist of three phases:

  • During phase I, the vaccine development was already deemed promising in pre-clinical experiments. A small group of participants then receive the vaccine to determine the overall safety and to see whether there are any serious side-effects.
  • When the vaccine is deemed safe for use during phase I, it moves to phase II – the vaccine is now administered in a larger group of healthy participants and, besides from the safety, it will also determine if the vaccine creates the desired immune response.
  • As the vaccine moves to phase III, it will be determined whether the vaccine is effective in those who are being exposed to the pathogen. Generally, a greater variety of age groups and people of more nationalities are included.       
  • Approval and licensing are done by different regulatory bodies. Many vaccines still undergo ongoing phase IV to ensure that the vaccine remains effective and up to date

What happened before the vaccine went to clinical trial?

In every vaccine development process, the safety of a vaccine needs to be established through laboratory tests and animal tests first. In these first tests, the vaccine was reported to protect rhesus macaque monkeys against respiratory distress from coronaviruses, as well as to activate an immune response.

The first clinical study (phase 1) was then continued, where the vaccine was deemed safe and well-tolerated and the neutralising antibodies occurred in all the participants after a second booster dose.

What comes next?

Once the safety of the vaccine has been established, the trial moves on to phase II/III - which, for the AZD1222 vaccine, is already under way in the UK and Brazil.

The study in the UK is ongoing and has already enrolled more than 4 000 participants, and an even larger study of 10 000 is due to start soon.

Brazil’s study is under way and has enrolled approximately 5 000 participants. A further study of the same vaccine candidate was later announced to take place in the US as well.

This phase will determine how well the vaccine will actually protect those who are exposed to SARS-Cov-2 and will also include more people of different ages and will be administered in various doses.

SA also involved

But the trials are not limited to the countries mentioned above - South Africa is included as well.

Health24 reported last month that a trial led by Wits University will consist of three groups and will enroll 2 000 volunteers, 50 of whom will be people living with HIV. The group consisting of HIV+ participants were trialled first. 

The study timeline started in June, and complete enrollment is expected to take place across multiple sites by mid-August of this year.

Planned follow-ups for up to 12 months after vaccination is expected, and participants will have fortnightly appointments to assess for any respiratory illness. They will also be investigated for Covid-19 in the event that they fulfil criteria that indicate illness.

But just two weeks into the trial, Professor Shabir Madhi said that scientists involved in the study are expecting results sooner than expected due to SA's high transmission rate. Results are, therefore, now anticipated to occur as soon as November or December this year. Previously, the team projected it might only occur in June 2021.

When will the vaccine be ready?

While the results from the phase II/III trials are yet to be determined, the promising early results of phase I/II trials puts AZD1222 ahead of the pack.

However, the data on this vaccine does not yet provide enough information to predict whether it will be more effective than other contenders yet.

But the developers are positive that the vaccine may be rolled out as early as September 2020, depending on the results of the final phases.  

According to AstraZeneca chief executive Pascal Soriot, the present assumption is that the data of these trials will be available around August and it will be known in September whether the vaccine is indeed effective.

Will there be enough vaccines?

According to AstraZeneca, it has made agreements with the Coalition for Epidemic Preparedness Innovations (CEPI), Gavi, the Vaccine Alliance, and the Serum Institute of India to double production capacity of the Covid-19 vaccine to two billion doses.

This collaboration will ensure that it can be supplied to many low- and middle-income countries and, according to Soriot, they are open to collaborate with other companies around the world to support access to the vaccine, with no profit.

The firm is also set to supply Europe with 400 million doses at no profit.           

What about other vaccine candidates?

While the Oxford/AstraZeneca vaccine is currently ahead, there are more than 160 vaccines in development, while 26 vaccines are already in human clinical trial phases.

One vaccine, developed by the Chinese company, CanSino Biologics, is also based on an adenovirus.

Their phase I results were published in May and results from phase II were published in July – this too showed a strong immune response.

The Chinese military then approved this vaccine on 25 June 2020 for a limited period of use in the military – this vaccine has not been approved for commercial use yet.

*Additional reporting by Zakiyah Ebrahim and Bevan Lakay

Image credit: Unsplash

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