Oxford's vaccine found to cut spread

One dose of the novel coronavirus vaccine produced by Astra-Zeneca and the University of Oxford provides protection from the virus for at least three months, according to a new analysis that also found the jab inhibits transmission.

Oxford University scientists said those who have received an injection are therefore less likely to spread the virus to others, a fact that had not previously been proved by research.

They also said the United Kingdom's dosing strategy, in which the second dose of the vaccine is administered 12 weeks after the first and which had been criticized by some other nations, has now been shown to be optimum.

Results from a preprint study published in the journal The Lancet revealed the so-called Oxford vaccine "shows sustained protection" during the three-month interval.

The researchers said the vaccine was 76 percent effective between day 22 and day 90 of receiving the first dose. The 22-day interval is the period of time the vaccine requires to induce an immune response.

The researchers also said there was a 67 percent reduction in positive swabs taken from vaccinated people in the UK.

"That's a big reduction of the number of individuals in the community who would be able to pass on to others," Oxford Vaccine Group Director Andrew Pollard told the BBC.

UK Health Secretary Matt Hancock said the "encouraging study" was a sign the "vaccine works and works well".

"This news about the Oxford vaccine is absolutely superb," Hancock said on Twitter.

"This should give everyone confidence that this jab works not only to keep you safe, but also to stop you from passing on the disease to others."

Strategy questioned

Several health experts had questioned the UK's approach of having a longer delay between doses than the three-to-four-week interval recommended by most vaccine makers.

The intent behind the strategy had been to offer a larger number of people a first dose. Critics argued there was insufficient evidence that protection would persist for such a long time.

The new study, which is yet to be peer-reviewed, provides valuable additional results to a smaller data set from interim trials that the UK's Joint Committee on Vaccination and Immunization, or JCVI, had relied upon to form the 12-week policy.

"There is good protection from the first dose, right up until the second dose is given, which is extremely good news," Pollard said.

"It also supports the policy recommendation made by the 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," he added.