Fully vaccinated people have just a one in 26 chance of picking up coronavirus if they come into contact with an infected individual, a study has shown.
Latest figures from Imperial College’s React-1 survey found that full vaccination halves the risk of getting an infection, compared to a one in 13 chance for unvaccinated people.
Analysis by Imperial also suggests double jabbed people are less likely to pass on the virus to others, and if they do catch Covid, their condition will be milder.
The study found that it took more rounds of PCR testing to detect coronavirus in vaccinated people than unvaccinated individuals – 27 cycles versus 23 – suggesting that there was less virus present in the fully jabbed.
Testing of 98,000 people found that unvaccinated people were three times more likely than fully vaccinated people to test positive, with a prevalence of 1.21 per cent of those swabbed suffering an infection compared to 0.4 per cent of the double-jabbed.
After adjusting for various factors, they found that vaccine effectiveness was 49 per cent among people who reported that they had been double jabbed.
“In other words, people who are double vaccinated are half as likely to be infected,” said Prof Paul Elliott, director of the React programme, and chair in epidemiology and public health medicine at Imperial.
“Vaccination is highly effective against serious outcomes,” he added.
The researchers from Imperial College said that it was uncertain whether or not there would be an increase in infections in September when schools returned and there was more indoor socialising.
Steven Riley, professor of infectious disease dynamics at Imperial, said that young people were driving infection rates prior to the recent dip in cases, adding: “So every additional person that gets vaccinated is taking a decent chunk of potential transmission out of what may or may not happen in September.
“There’s been a drop, a plateau, now, and I think it is challenging to make any kind of prediction over the summer months. There is uncertainty around what might happen in September when schools return and increased indoor mixing.”
The study found that the delta variant had “completely taken over” from the alpha variant, with 100 per cent of sequenced swabs testing positive for the mutated virus.
Separate Public Health England data shows that between June 21 and July 19, 1,788 people were admitted to hospital after testing positive for delta.
Of these, 970 (54.3 per cent) were unvaccinated, while 530 (29.6 per cent) had received both doses of the vaccine.
In total, 3,692 people have been hospitalised with the delta variant, of whom 2,152 (58.3 per cent) were unvaccinated and 843 (22.8 per cent) were fully vaccinated.
Nadhim Zahawi, the vaccines minister, said: “Today’s results show the positive impact of the vaccination programme with those who are double jabbed less likely than unvaccinated people to get the virus and less likely to pass on this awful disease to those around them.”
From the end of September the Government plans to make full vaccination a condition of entry to high-risk settings with large crowds, such as nightclubs.
Sajid Javid, the Health Secretary, added: “Today’s report shows the importance of taking personal responsibility by self-isolating if you are contact-traced, getting tested if you have symptoms and wearing face coverings where appropriate.
“I urge anyone who has yet to receive a vaccine to get jabbed and take up both doses – the vaccines are safe and they are working.”