First trial of the Oxford vaccine shows an immune response
Last week there were numerous media reports that ‘the vaccine’ for COVID-19 works and produces an immune response. But things aren’t as simple as that – firstly there isn’t just one potential vaccine, and even with the Oxford vaccine in question, researchers still don’t have the ultimate evidence they need to show ‘it works’ to prevent disease.
The COVID-19 pandemic has seen vaccine research, development and production on an unprecedented scale. There are over 150 different vaccines currently in development worldwide, though only 26 are in clinical trials. One of the first to reach clinical trials was the University of Oxford vaccine. The research team used a vaccine technology they had previously developed for SARS, and their first trial in 1,000 people started in April. This showed promising signs that it was safe and that recipients were producing antibodies against the COVID virus. So, the vaccine moved onto larger (phase 3) trials, firstly in 10,000 people in the UK, then globally.
The announcement that has caused a media reaction was first published results showing people produce antibodies following vaccination. Evidence from the larger trials is needed to show if it prevents people getting COVID disease. As there are at least 5 other vaccines also in phase 3 trials, we will have to wait to see which vaccine, or vaccines, will be proven to prevent infection.
Where did the story come from?
The University of Oxford issued a press release last week following publication of their first trial results in the peer-reviewed journal, The Lancet.
What is the basis for the claim?
The University of Oxford vaccine (developed in collaboration with AstraZeneca) uses an adenovirus as a ‘vector’ to carry genetic material from SARS-CoV-2, the coronavirus, into cells. Adenoviruses are very common viruses that cause mild respiratory or gastrointestinal illness. The adenovirus has had its replicating genes cut out (meaning it can’t cause infection itself) and genes that code for the characteristic spike protein on SARS-CoV-2 have been inserted. This should mean the person produces antibodies against this protein.
Their first clinical trial (phase 1) recruited 1,000 healthy adults (aged 18 to 55) and randomly allocated them to receive the vaccine or a comparator (a meningitis vaccine). The main aims of this trial were to see that the vaccine was safe and whether it may be able to produce an immune response. The preliminary findings were positive: vaccine recipients produced antibodies against the SARS-CoV-2 spike protein and laboratory tests have demonstrated that these antibodies can inactivate the virus. Side effects such as feeling feverish, headache and muscle aches were common among vaccine recipients, but there were no serious adverse effects.
With these promising results, the vaccine moved onto larger trials in May/June. The phase 3 recruited 10,000 healthy adults, while a phase 2 subpart has recruited small groups of adults over 55 and children. Since then other phase 3 trials using the vaccine have started in Brazil and South Africa. We need to await the results of these trials – comparing the infection rate in the vaccine vs the control group – to know whether the vaccine actually ‘works’ to prevent infection.
But the Oxford vaccine isn’t the only potential vaccine: at last five other vaccines from different developers/manufacturers also went into phase 3 trials in July. These are using different vaccine technologies: three use inactivated SARS-CoV-2 and two use lipid (fat) particles to transport the genetic material from the virus. Like the Oxford vaccine, all of these vaccines trials will need to look at whether the vaccine is safe and prevents infection. How long it takes to get this evidence will depend on the transmission rate in areas where it is tested.
What do trusted sources say?
In April 2020, the WHO issued a public statement signed by experts worldwide who were working towards developing vaccines against COVID-19. They stated ‘while a vaccine for general use takes time to develop, a vaccine may ultimately be instrumental in controlling this worldwide pandemic. In the interim, we applaud the implementation of community intervention measures that reduce the spread of the virus and protect people.’
The WHO also hosts a regularly updated landscape of the global vaccines and their current stage in development.
Analysis by EIU Healthcare, supported by Reckitt Benckiser
- Folegatti PM, 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. 2020 Jul 20. https://www.thelancet.com/journals/lancet/article/PIIS0140-6736(20)31604-4/fulltext
- University of Oxford. News & Events. New study reveals Oxford coronavirus vaccine produces strong immune response. (Accessed 31 July 2020) https://www.ox.ac.uk/news/2020-07-20-new-study-reveals-oxford-coronavirus-vaccine-produces-strong-immune-response
- Draft landscape of COVID-19 candidate vaccines. https://www.who.int/publications/m/item/draft-landscape-of-covid-19-candidate-vaccines
- Public statement for collaboration on COVID-19 vaccine development. 13 April 2020.