Oxford jab protects 12 weeks after single dose and may cut transmission – study

Nina Massey, PA Science Correspondent
·3-min read

The University of Oxford’s coronavirus vaccine offers protection of 76% up to 12 weeks after a single dose and may reduce transmission by 67%, according to a new study.

After the second dose, vaccine efficacy from two standard doses is 82.4% with the three-month interval being used in the UK, researchers from the University of Oxford say.

The data from the study, which has not yet been peer reviewed, supports the four to 12-week prime-boost dosing interval that many global regulators have recommended.

Analyses of positive coronavirus swabs in the UK population suggest the vaccine may have a substantial effect on transmission of the virus, with a 67% reduction in positive swabs among those vaccinated with the Oxford/AstraZeneca jab.

Before these results, little was known about how effective the Covid-19 vaccines were at preventing transmission of the disease.

The findings indicate that those who have been vaccinated are not only protected from the disease, but that they are not likely to pass on the virus to anyone.

The preprints reveal that vaccine efficacy is higher with longer intervals between doses, and that a single dose of the vaccine is 76% effective from 22 to up to 90 days post-vaccination.

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Professor Andrew Pollard, chief investigator of the Oxford Vaccine Trial, and study co-author, said: “These new data provide an important verification of the interim data that was used by more than 25 regulators including the MHRA (Medicines and Healthcare products Regulatory Agency) and EMA (European Medicines Agency) to grant the vaccine emergency use authorisation.

“It also supports the policy recommendation made by the Joint Committee on Vaccination and Immunisation (JCVI) for a 12-week prime-boost interval, as they look for the optimal approach to roll out, and reassures us that people are protected from 22 days after a single dose of the vaccine.”

In the paper, which is currently under review at The Lancet, the researchers report on an analysis of additional data to include information from the trial up to December 7 2020.

This includes a further 201 cases of primary symptomatic Covid-19 (332 cases from 131 reported on previously).

They report that the effect of dosing interval on efficacy is pronounced, with vaccine efficacy rising from 54.9% with an interval of less than six weeks to 82.4% when spaced 12 or more weeks apart.

Health Secretary Matt Hancock welcomed the findings, saying “this news about the Oxford vaccine is absolutely superb”. He added that “vaccines are the way out of the pandemic”.

Prime Minister Boris Johnson said the data from the study was “really encouraging”.

The findings suggest that it is the time between doses and not the dosing level which has a great impact on the efficacy of the vaccine.

Researchers say this is in line with previous research supporting greater efficacy with longer prime-boost intervals done with other vaccines such as influenza, Ebola and malaria.

In the coming days, the authors hope to also report data regarding the new variants, and expect the findings to be broadly similar to those already reported by fellow vaccine developers.