On Jun. 25, 2021, researchers from the University of Oxford released their findings about the so-called ”correlates of protection’ against symptomatic COVID-19; potentially a tool to speed up safe development of new vaccines which may assist regulators in assessing the likely potency of any new COVID-19 vaccine without the need for Phase III efficacy trial data.

Writing on MedRxiv, they reported that higher levels of anti-spike, anti-RBD IgG, and neutralising antibody titres were associated with a greater degree of protection against COVID-19 ﾖ defined as a PCR positive test with at least one symptom present.

These data were then used to build a model to extrapolate the levels of antibody associated with varying degrees of protection, providing estimates for a range of vaccine efficacies from 50% to 90%, using three different assays. Standard values are also provided to bridge between assays from different laboratories.

The study also confirms previous indications that there is no single level on any of the binding or neutralising antibody assays used, that provides full protection against COVID-19. The results link immune responses to expected population protection after 2 doses, but cannot be used to check protection of an individual who has been vaccinated or protection conferred by a single dose.

The findings were submitted for peer-review, and the researchers hope to communicate their findings fully in scientific literature in due course