The researchers said the method “can be used to extrapolate efficacy estimates for new vaccines where large efficacy trials cannot be conducted,” but cautioned that more work is needed to assess correlates for emerging variants.
In their paper (pdf), which was submitted for peer review for publication in a scientific journal on Thursday, researchers outlined how they examined the concentration of several antibodies in the blood of trial participants after they had received the COVID-19 vaccine developed by AstraZeneca and Oxford University.
They then compared that data with blood readings data of both trial volunteers who later contracted symptomatic COVID-19, and those trial volunteers who did not.
“There is an urgent need to increase supply of vaccines for the world, but development and approval of new vaccines takes many months. We hope that the use of correlates by developers and regulators could speed up the process,” said Professor Andrew Pollard, director of the Oxford Vaccine Group and lead investigator on the Oxford Vaccine Trial.
Researchers and regulators around the globe are working on such benchmarks which may allow slower companies in the COVID-19 vaccine development race to provide evidence of efficacy without having to conduct trials with tens of thousands of volunteers.
Those mass trials have so far relied on participants to contract the disease in their normal lives to provide vaccine efficacy results. That becomes more of a challenge where vaccination coverage is already high and the virus is not circulating widely.
The traditional clinical trials also require many participants to get a placebo as a comparison to those who receive the experimental vaccine, posing an ethical dilemma where approved shots are available.
Reuters contributed to this report.