First data shows two doses of Oxford / AstraZeneca vaccine elicited a good immune response

LONDON (Reuters) – The University of Oxford’s COVID-19 vaccine candidate has a better immune response when a full two-dose regimen is used rather than a full dose followed by a half-dose booster, a the university said Thursday, citing data from early trials.

The developers of the vaccine candidate, which was licensed to pharmaceutical company AstraZeneca, have already published subsequent trial results showing higher efficacy when a half dose is followed by a full dose, compared to a regimen with two full doses. However, there is still work to be done to confirm this result.

The latest details from the Phase I and 2 clinical trials released Thursday made no reference to the half-dose / full-dose regimen, which Oxford said was “unplanned” but approved by regulators.

Once seen as the pioneer in the development of a coronavirus vaccine, the British team has been overtaken by US drug maker Pfizer, whose injections were rolled out in Britain and the United States this month.

Data published earlier from the latest Phase 3 trials showed efficacy to be 62% for trial participants given two full doses, but 90% more robust for a smaller subgroup receiving first half, then a full dose.

In its statement on Thursday, the university said it had explored two dosing regimens in preliminary trials, a full-dose / full-dose regimen and a full-dose / half-dose regimen, being studied as a possible strategy ” dose savings ”.

“The booster doses of the vaccine both induce stronger antibody responses than a single dose, with the standard dose / standard dose inducing the best response,” the university said in a statement.

The vaccine “stimulates broad functions of antibodies and T cells,” he says.