Coronavirus: How will the Covid-19 vaccine trial work?

Researchers at the University of Oxford are starting human trials for a potential coronavirus vaccine candidate.

But what does the trial involve, and how will it work according to the Oxford Vaccine Group?

– What is the purpose of the study?

The trial will analyse whether healthy people can be protected from Covid-19 with the vaccine created by the Oxford Vaccine Group – ChAdOx1 nCoV-19.

It will allow researchers to assess the safety of the candidate, and its ability to generate an immune response.

– How does the study work?

Up to 1,102 participants will be recruited across multiple study sites in Oxford, Southampton, London and Bristol.

The volunteers will be randomly allocated to receive either the ChAdOx1 nCoV-19 vaccine or a licensed meningitis vaccine that will be used as a control for comparison.

At the start of the trial, a separate small group of 10 volunteers will receive two doses of the candidate four weeks apart.

– Who can participate?

Volunteers must be aged 18-55, and must not have tested positive for Covid-19.

They must also be in good health, not be pregnant or breastfeeding, and must not have previously taken part in a trial with an adenoviral vaccine or received any other coronavirus vaccines.

– How will the trial work?

The dose used in the trial was chosen based on previous experiences with other ChAdOx1 based vaccines.

Participants will not know whether they have received the Covid-19 vaccine or the control vaccine until the end of the trial.

On day one, the first two participants will be vaccinated, one with the ChAdOx1 nCoV-19 vaccine and one with the control vaccine. They will be monitored for 48 hours.

On day three, six more volunteers will be vaccinated, half with the Covid-19 vaccine and three with the control vaccine. They will also be monitored for 48 hours.

On the fifth day, researchers will progress to vaccinating larger numbers of participants.

– What happens next?

The participants will be given an e-diary to record any symptoms they experience in the seven days after receiving the vaccine.

They will also record if they feel unwell for the following three weeks.

The volunteers will attend a series of follow-up visits, during which blood samples will be taken to assess their immune response, and their observations checked.

If they develop Covid-19 symptoms during the study, they can contact a member of the clinical team, who will check if they have become infected with the virus.

If a participant becomes very unwell they will be reviewed by staff at the hospital.

– When will the results be available?

The statisticians will compare the number of infections in the control group with the number of infections in the vaccinated group.

Therefore, it is necessary for a small number of study participants to develop Covid-19.

How quickly researchers reach the numbers required depends on the levels of virus transmission in the community.

If transmission remains high, enough data may be available in a couple of months but if transmission levels drop, this could take up to six months.

– What is the vaccine?

ChAdOx1 nCoV-19 is made from ChAdOx1, which is a weakened version of a common cold virus (adenovirus) that causes infections in chimpanzees.

It has been genetically changed so it is impossible for it to grow in humans.

Researchers hope their version will make the body recognise and develop an immune response to the spike protein – recognisable in images of the virus – that will help stop Covid-19 from entering human cells and therefore prevent infection.