The Oxford coronavirus vaccine has successfully blocked the virus in a small study of monkeys, researchers reported this week.
According to the study, all inoculated monkeys developed protective antibodies against the virus within 28 days, prior to exposure to high levels of the virus. The monkeys were given one shot of the covid-19 vaccine candidate.
The results of the study, conducted in 6 rhesus macaques monkeys, which has not yet been peer reviewed, were published to the preprint server bioRxiv on 13 May. The findings led to the vaccine entering clinical trials late last month. Macaques monkeys, which share 93% of their DNA with humans, are considered to be good proxies for how similar vaccines work in humans.
Following high levels of exposure to the novel coronavirus, the vaccine candidate prevented damage to the lungs, as well as replication there. None of the monkeys developed pneumonia, the most common coronavirus complication. There was also no evidence of immune-enhanced disease, where a vaccine makes the disease worse, which is a reassuring find for researchers. However, there was virus replication in the nose.
The authors of the paper wrote: “We observed a significantly reduced viral load in bronchoalveolar lavage fluid and respiratory tract tissue of vaccinated animals challenged with SARS-CoV-2 compared with control animals, and no pneumonia was observed in vaccinated rhesus macaques.
“Importantly, no evidence of immune-enhanced disease following viral challenge in vaccinated animals was observed.”
The team is led by Professor of Vaccinology Sarah Gilbert, at the Jenner Institute, University of Oxford. The vaccine is currently in Phase 1 clinical trials in 1000 patients, and aim to enter late-stage clinical trials by the summer. The university has struck a partnership with British drug producing firm AstraZeneca and are optimistic about large scale production by September.
Professor Sir John Bell, regius professor of medicine at the University of Oxford, told BBC4’s Today programme ” that he hoped to get “some signal” about whether the vaccine is working by June.
The science:
Source: Covid-19 vaccine trial, University of Oxford
A chimpanzee adenovirus vaccine vector (ChAdOx1), developed at Oxford’s Jenner Institute, was chosen as the most suitable vaccine technology for a SARS-CoV-2 vaccine as it can generate a strong immune response from one dose and it is not a replicating virus, so it cannot cause an ongoing infection in the vaccinated individual.
This also makes it safer to give to children, the elderly and anyone with a pre-existing condition such as diabetes. Chimpanzee adenoviral vectors are a very well-studied vaccine type, having been used safely in thousands of subjects, from 1 week to 90 years of age, in vaccines targeting over 10 different diseases.
Coronaviruses have club-shaped spikes on their outer coats. Immune responses from other coronavirus studies suggest that these are a good target for a vaccine. The Oxford vaccine contains the genetic sequence of this surface spike protein inside the ChAdOx1 construct.
After vaccination, the surface spike protein of the coronavirus is produced, which primes the immune system to attack the coronavirus if it later infects the body. Prof. Gilbert and team have previously developed a vaccine for another human coronavirus disease, which is Middle East Respiratory Syndrome (MERS), and this has shown promise in early clinical trials.