COVID vaccines have slashed infection rates in NHS staff by 50 per cent within 12 days, a study has shown.
Professor Tim Spector, who led the research from King’s College London, said the findings were “fantastic news”.
Pharmacist Josh Athwal receives an injection of the Oxford/Astrazeneca coronavirus vaccine at The Black Country Living Museum in DudleyCredit: PA:Press Association
It suggests the vaccines are helping prevent people catching the virus and therefore testing positive, which would also slow down spread of the disease.
The jabs have already been proven in clinical trials to be highly effective at preventing someone from developing severe disease or dying.
But if they can also prevent people transmitting the virus, it would help come out of lockdowns sooner, the Government’s scientific advisers say.
Dr Anna Goodman, a consultant in infectious diseases and an investigator on the Oxford vaccine trial, warned “there are still some people with the virus” after vaccination – as shown in this data.
At a webinar setting out the findings, she said: “When you’ve had your vaccine, you can’t just presume yourself to be 100 per cent.
“You can’t go and visit an elderly relative and presume you’ll be absolutely fine – that’s not how the vaccines work.”
The first two-week period [after vaccination], there’s like zero protection
Professor Tim Spector
Prof Spector added vaccinated people shouldn’t change their behaviour – such as wearing face masks – while infections are so high.
And he warned the effects of the jabs effects did not kick in till about 12 days after the dose.
Prof Spector said: “This brings up the other point that at no point after you have had a vaccine are you 100 per cent protected.
“But particularly that first two-week period, there’s like zero protection.
“And many people might be much more relaxed and there’s some evidence that they aren’t as concerned about prevention of a vaccine, and might rush up to relatives and go on public transport more.
“So that’s a really important public health message for everybody, that actually the risks are really high just after you’ve had the vaccination but then it starts to improve.”
It comes after scientists warned yesterday the risk of infection in Israel doubled in the first eight days after vaccination – possibly because people become less cautious.
This graph shows how the percentage of healthcare workers testing positive for Covid dropped by half compared with those not given the jab. The effect happens from 12 weeks after the first dose. The graph also shows how infection overall have declined in recent weeksCredit: ZOE COVID SYMPTOM STUDY
DROP IN CASES
The data focused on the healthcare workers who have been vaccinated and report to the Zoe Covid Symptom Study using the mobile app.
There are 220,391 UK healthcare workers on the app, around three quarters of which have logged a vaccine, and around 13,000 coronavirus swab test results per week.
Christina Hu, head of product at the study, said the reduction of 50 per cent remains consistent as the overall population’s Covid case numbers decline, meaning that the cases did not go down just because the overall infection rate in the UK has.
Professor Spector said: “It is fantastic news really that we were seeing this without having to wait three months to get a result.”
People need to have two doses of the vaccines being administered – from Pfizer/BioNTech and AstraZeneca/Oxford.
But evidence is increasingly suggesting even after the first dose, the immune response is strong, giving confidence in the Government’s strategy to delay the second dose by three months.
Prof Spector said: “I think this is the first sign that in real life, outside trials, what the effect is of a single dose.”
The professor of genetic epidemiology said the researchers were very interested to see if that 50 per cent drops even further over time, especially up to 12 weeks.
Prof Spector said: “Because this would seem to be vindicating the approach of the Government at the moment about the 12-week delay, if we can get at least 50 per cent protection, very rapidly.”
Care home worker Marie Annn Gynn receiving the AstraZeneca/Oxford Covid-19 vaccination at the Royal Cornwall Showground in WadebridgeCredit: Getty Images – Getty
The UK Government has decided to leave a gap of 12 weeks between two doses, rather than 21 days, in a bid to get more people vaccinated with at least one dose sooner.
The approach was initially met with some hesitancy, with little data to support it from clinical trials.
But ongoing studies to assess how effective vaccines are after a single dose and with a 12-week gap between doses.
On Tuesday, data released by the University of Oxford researchers said their own research showed one dose was 76 per cent effective at preventing severe disease and death for up to three months.
After the second dose is given, efficacy goes up to 82.4 per cent. But given after six weeks, the effectiveness dropped to 54.9 per cent, suggesting a longer gap between doses is best.
The university said it “supports the policy” of leaving a 12-week gap between the first and second dose adopted by the UK Government.
Similarly, data from Israel, studied by the University of East Anglia (UEA), showed a single shot of the Pfizer vaccine gives 90 per cent Covid protection after 21 days, at which point researchers believe it is “unlikely” to majorly decline.
The Oxford findings were also the first glimmer of hope that the vaccine cuts transmission by around 67 per cent.
Dr Andrew Pollard, chief investigator of the Oxford vaccine trial and co-author of the paper, told BBC Radio 4 Today that the Oxford/AstraZeneca jab could have a “huge impact” on transmission.
However, scientists cautioned that there would still be risks of coronavirus infection and deaths for several months yet in those unvaccinated.
Some restrictions could last until spring 2022 because of this, according to Paul Hunter, professor in medicine at UEA.