LAST UPDATE | 20 Jul 2020

A TRIAL OF a potential vaccine to protect against Covid-19 has shown it to be safe and that it induces an immune reaction, according to preliminary results published today. 

Researchers at Oxford University conducted a Phase 1/2 trial involving 1,077 healthy adults found the vaccine induced strong antibody and T cell immune responses for up to 56 days. 

The trial is at too early a stage to be sure if it could meet the requirements needed for an effective vaccine against Covid-19. It is still likely to be some time before this or any vaccine becomes available. 

The results, however, are being described as encouraging as the response it provoked in the body show this vaccine could find and attack the virus in our cells.

Lead author of the study published in the Lancet today, Professor Andrew Pollard explained: “The immune system has two ways of finding and attacking pathogens – antibody and T cell responses. This vaccine is intended to induce both, so it can attack the virus when it’s circulating in the body, as well as attacking infected cells.

We hope this means the immune system will remember the virus, so that our vaccine will protect people for an extended period. 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.

The next step will be to proceed to Phase Three trials, which are more in-depth and usually involve a greater number of participants. For medicines to be deemed effective and be given regulatory approval, a set of rigorous tests and data must be obtained.

Study co-author Professor Sarah Gilbert said: “There is still much work to be done before we can confirm if our vaccine will help manage the Covid-19 pandemic, but these early results hold promise.

As well as continuing to test our vaccine in phase 3 trials, we need to learn more about the virus – for example, we still do not know how strong an immune response we need to provoke to effectively protect against SARS-CoV-2 infection.

Study details

Phase two – in the UK only – and phase three trials to confirm whether it effectively protects against the virus are taking place in the UK, Brazil and South Africa.

The trial included 1,077 healthy adults aged 18-55 years with no history of Covid-19, and took place in five UK hospitals between April 23 and May 21.

The data included in the paper covered the first 56 days of the trial and is ongoing.

The participants either received the new vaccine (543 people), or the meningitis vaccine (534 people).

Some of them – 56 given the vaccine, and 57 in the control group – were also asked to take paracetamol before and for 24 hours after their vaccination to help reduce vaccine-associated reactions.

All volunteers gave additional blood samples and underwent clinical assessments to determine if the vaccine was safe and whether it provoked an immune response.

The most commonly reported reactions were fatigue and headache, but some participants also reported pain at the injection site, muscle ache, malaise, chills, feeling feverish, and high temperature.

In addition, in the 10 people who received the extra dose of the Covid-19 vaccine, side effects were less common after the second dose.

The research found that the vaccine stimulates an antibody and T-cell response.

Antibodies are proteins produced by the blood in response to antigens, which are harmful substances that come from outside the body, such as from viruses or bacteria.

If the non-specific immune cells which respond to any invader instantly cannot tackle it, the T-cells come into play.

They take two forms – helper T-cells and killer T-cells.

The latter attack the virus directly.

T-cell responses targeting the Sars-CoV-2 spike protein were markedly increased in the 43 participants studied, peaking 14 days after vaccination.

This level declined slightly by day 56 of the trial.

Researchers also found that the T-cell response did not increase with a second dose of the vaccine.

Antibody responses in those given a single dose peaked by day 28, and remained high until the measurement at day 56 in the trial.

This response was boosted by a second dose.

Four weeks after vaccination, neutralising antibody responses against Sars-CoV-2 were detected in 32 of 35 participants, and in 35 of 35 participants – depending on the test – who received a single dose of the vaccine.

These responses were also present in all participants who had a booster dose of the vaccine.

The authors note a number of limitations to their study, saying more research is needed to confirm their findings in different groups of people – including older age groups, those with other health conditions, and in ethnically and geographically diverse populations.

In the current trial, 91% of participants were white and the average age of participants was 35 years.