British scientists start Phase II on COVID-19 vaccine

The study sponsored by AstraZeneca plc is the third pivotal test of a COVID-19 vaccine that expresses SARS-CoV-2 antigens directly in human cells or in a viral vector. Last week, US-based Moderna Inc. announced headline results of a Phase II test of its mRNA vaccine, which led to production of antibodies that neutralised SARS-CoV-2 in the test tube. Results of Phase II trials with Chinese CanSino Ltd.’s adenoviral vaccine candidate published in Lancet gave similar results. However, the Chinese researchers warned that nobody knows what antibody titer is needed to neutralise the coronavirus in humans. According to the British researchers, a significant proportion of vaccines that are tested in clinical trials don’t work.

A Phase I trial of the adenoviral vector vaccine developed by the British consortium in collaboration with Dutch Halix NV and German Merck KGaA began in April. More than 1,000 immunisations have been completed and follow-up is currently ongoing. In the pivotal Phase II/III study, the researchers plan to enrol up to 10,260 adults and children and will involve a number of partner institutions across the UK. Within the Phase II trial, the ChAdOx1 nCoV-19 vaccine or a licensed vaccine (MenACWY) that will be used as a ‘control’ for comparison will also be tested in a small number of older adults and children. For adults aged 50 to over 70 and children aged 5-12, researchers will be assessing the immune response to the vaccine. The Phase III study is powered to assess how well the vaccine works to prevent people from becoming infected and unwell with COVID-19.

ChAdOx1 nCoV-19 is made from a virus (ChAdOx1), which is a weakened version of a common cold virus (adenovirus) that causes infections in chimpanzees. It has been genetically changed so that it is unable to replicate in humans.

Collaborators at Rocky Mountain Laboratories (NIAID/NIH) demonstrated good safety and efficacy of a single dose of ChAdOx1 nCoV-19 in the rhesus macaque model that they had previously established. Further animal studies are underway in Australia and the UK, and the results will be published once they are complete.

If successful, the vaccine now dubbed AZD1222 will be produced by Emergent Biosolutions Inc as part "Operation Warp Speed", the US programme to accelerate COVID-19 countermeasures, and could gain US$1.2bn of funding for making it available.