Falling infection rates in the UK could scuttle Oxford University’s SARS-CoV-2 vaccine trial
Researchers at Oxford University who were to carry out human trials of a SARS-CoV-2 vaccine face a strange paradox. With community infection on the wane in the UK, the chance of the trial leading to a ‘no result’ scenario are now almost 50%, as per one of the teams that came up with the vaccine. The trial would involve 10,260 volunteers across the country. To be able to study whether the vaccine is effective or not, the researchers will have to compare the number of infections in the control group with the number of infections in the vaccinated group. For this purpose, at least a critical number of trial subjects need to contract SARS-CoV-2 infection.
Now, how soon the critical numbers are reached will depend on the level of virus transmission in the community. If fewer than 20 of the 10,000 volunteers test positive, the trial would have been inconclusive. To beat this possibility, the university has decided to prioritise the recruitment of those with a higher exposure to the virus, and thus a higher chance of getting infected—such as health workers and frontline support staff. If the infection rates fall drastically—and this is an end no one would want to wish against—this trial would have to be canned. But, there are other vaccines that are already under trial—both the US-based Moderna and China-based CanSino have reported early positive results with their candidates—and these could still hold out hope. Even if we do get a successful vaccine candidate, the real test would be in the length of immunity it provides.