Researchers at the University of Oxford who are developing an adenovirus-based vaccine for COVID-19, with British big pharma AstraZeneca, have released preclinical scientific data supporting their vaccine efforts.
The research supports the ongoing Phase I study in the UK, which is the most advanced such effort in the country. It is one of eight projects around the world that are currently testing candidate vaccines for COVID-19 in humans, according to the WHO.
The study was published on the preprint server bioRxiv, a platform set up to allow early release of scientific research to the scientific community before being peer reviewed. The speed of the vaccine effort against COVID-19 has made it difficult to follow normal procedures for validation and publication of scientific research, which typically take several months.
The research, carried out with colleagues at the National Institutes of Health in the U.S., took place in mice and rhesus macaque monkeys. The vaccine being tested is based on a chimpanzee adenovirus—similar to the common cold virus—that has been engineered so it can’t reproduce in human cells. It simply acts as the carrier for the COVID-19 vaccine.
The researchers believe it will be successful, as although it is still experimental, they have previously tested this vaccine platform quite against several other similar pathogens. For example, they tested a vaccine made using the same chimpanzee adenovirus vector against another coronavirus—Middle East respiratory syndrome coronavirus—with good initial results.
Typically, vaccines are evaluated based on whether they can trigger the production of antibodies in against a disease and whether immune cells in the system of the animal or person being immunized actively respond to the vaccine. The researchers showed that mice and macaques injected with the candidate vaccine had a strong immune response to it and developed antibodies as well as a cell-based response.
In a placebo-controlled trial, six vaccinated macaques and three unvaccinated controls were exposed to the virus a month after receiving one dose of the vaccine. The team saw a significantly lower number of viral particles in liquid and fluid taken from the lungs of the animals in the study that had been vaccinated compared with the controls. They also saw no signs of pneumonia in vaccinated monkeys, whereas two out of three controls did show signs of this Covid-19 complication.
Importantly none of the vaccinated animals showed signs of aggravated disease, something that has been seen in the past.
“It is one of the hurdles to be passed by the Oxford vaccine and it has cleared it well,” commented Stephen Evans, Ph.D, London School of Hygiene & Tropical Medicine, who was not involved with the research.
“The most important finding to me is the combination of considerable efficacy in terms of viral load and subsequent pneumonia, but no evidence of immune-enhanced disease. The latter has been a concern for vaccines in general, for example with vaccines against respiratory syncytial virus (RSV), and for SARS vaccines. This was a definite theoretical concern for a vaccine against SARS Cov-2 and finding no evidence for it in this study is very encouraging.”