Oxford vaccine could cut transmission of Covid by more than 60 percent, study suggests

UK ‘is correct’ in AstraZeneca vaccine ruling says expert

Top scientists currently warn that people who are vaccinated must stick to lockdown rules in case they can still carry and spread the virus. Oxford University researchers last night revealed the first evidence that their jab could have a “substantial effect” on transmission by stopping many people spreading infection. Swabs obtained from volunteers in the UK section of the trial showed a 67 percent reduction in people carrying the virus after the first dose of the vaccine.

The latest analysis of trial data also showed a single dose of the vaccine offered 76 percent protection against symptomatic infection for three months.

Efficacy rose to 82 percent after a second dose given at least 12 weeks later – and a longer gap between jabs provided better immunity.

Health Secretary Matt Hancock said: “This is a hugely encouraging study and further reinforces our confidence that vaccines are capable of reducing transmission and protecting people from this awful disease. This report shows the Oxford vaccine works, and works well.”

The study included data from 17,000 people enrolled in trials in the UK, Brazil and South Africa.

Vaccine efficacy after one dose was 76 percent from day 22 – the time needed for immunity to develop – to day 90 after inoculation.

Protection did not appear to decline over three months and was then boosted to 82 percent with a second dose.

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When two doses were given less than six weeks apart, efficacy dipped to 55 percent.

Sharing the results on Twitter, Prof Katie Ewer, a senior immunologist at University of Oxford, said: “No-one in a population of 12,408 people vaccinated with a single dose of ChAdOx1 nCo-19 was hospitalised with Covid-19 from 22 days after immunisation.

“This is the most important thing! Seventy-six percent efficacy against symptomatic Covid-19 is great, but zero people hospitalised is everything.”

Chief investigator Prof Andrew Pollard said the data supported earlier results used by 25 regulators including the UK’s Medicines and Healthcare Products Regulatory Agency (MHRA) to approve the vaccine for emergency use.

 He said: “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 rollout, and reassures us that people are protected from 22 days after a single dose of the vaccine.”

The preprint study is currently under review at The Lancet medical journal.

Meanwhile, a University of Cambridge study has suggested one dose of the Pfizer/BioNTech coronavirus vaccine may not be enough to protect some older people from Covid-19 infection.

Scientists tested blood samples from 26 volunteers three weeks after they received the first dose.

They found seven did not have sufficient levels of antibodies to neutralise the original strain of coronavirus, all of whom were aged over 80.

 A total of 15 people aged over 80 were included in the study.

After receiving a second dose three weeks after the first, all were able to neutralise the virus.

The Government has said it is safe to extend the gap between doses of the Pfizer vaccine from the recommended three weeks to 12. But Dr Dami Collier, co-investigator on the studies, said: “Our data suggest that a significant proportion of people aged over 80 may not have developed protective neutralising antibodies against infection three weeks after their first dose.

“But it’s reassuring to see that after two doses, serum from every individual was able to neutralise the virus.”

The team tested the participants’ antibodies by creating a synthetic version of the Sars-CoV-2 virus, known as a “pseudovirus”, in the lab.

After testing with the original virus, they added in eight mutations found in the UK variant. Twice the level of antibodies was needed to neutralise that strain but the researchers said the vaccine should still be effective.

However, when the more worrying E484K mutation – first seen in the South African variant – was added, the required level of antibodies increased 10-fold.

Professor Ravi Gupta, who led the study, said the vaccine was likely to be less effective when dealing with this mutation.

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