The latest study says Fully vaccinated people were three times less likely than unvaccinated people to test positive for the Covid-19 infection- new research was led by researchers at the Imperial College London.
The new research is based on swab tests taken by nearly 98,233 people themselves at home and their samples were analysed by PCR testing between June 24 and July 12. Of these, 527 tested positive and 254 of these were successfully analysed in the lab to determine their origins, 100 per cent of which were Delta variants.
Key Findings of the New Study on COVID Vaccinated infection chances
- 527 positives from 98,233 swabs, giving a prevalence of 0.63% or 1 in 160 people;
- more than a four-fold rise in prevalence compared to the last full report which covered 20 May-7 June, increasing from 0.15% to 0.63;
- unvaccinated people were three times more likely than fully vaccinated people to test positive for COVID-19, with prevalence at 1.21% and 0.40%;
- double vaccinated people in the most recent round were estimated to have around 50 to 60% reduced risk of infection, including asymptomatic infection, compared to unvaccinated people;
- those who were fully vaccinated may be less likely to pass on the virus to others than those who have not received a vaccine;
- prevalence was highest in London at 0.94%, up from 0.13% in round 12, although this growth appeared to be slowing at the end the study period;
during Round 13, the R number was estimated at 1.19, corresponding to a doubling time of 25 days; - of the 254 positive samples sequenced for variants, 100% were the Delta variant, compared to 78.3% in the last report at the end of May (round 12);
a substantial increase in prevalence in all age groups under the age of 75; - prevalence is nine-fold higher in 13-17 year-olds at 1.56% compared with 0.16% in round 12;
- 3.84% of double-vaccinated individuals who reported recent contact with a known COVID-19 case tested positive, compared to 7.23% of unvaccinated individuals; and
- When comparing the REACT infection data with official NHSE hospitalisation data, since mid-February there has been a weakening in the relationship between infections and hospitalisations and deaths. Since mid-April there are signs of the relationship between infections and hospitalisations coming back together. More time is needed to understand what this means and to identify any trends.
People who were unvaccinated had a three-fold higher prevalence than those who had received both doses of Covid-19 vaccine, at 1.21 per cent compared to 0.4 per cent.
In addition, analyses of PCR test results also suggest that fully vaccinated people may be less likely than unvaccinated people to pass the virus on to others. This is due to having a smaller viral load on average and therefore, likely spreading less virus.
The study carried out in partnership with Ipsos MORI is available in a pre-print report and will be submitted for peer-review.
“These findings confirm our previous data showing that both doses of a Covid-19 vaccine offer good protection against getting infected. However, we can also see that there is still a risk of infection as no vaccine is 100 per cent effective, and we know that some double vaccinated people can still fell ill from the virus,” said Paul Elliott, School of Public Health at Imperial College London.
“So even with the easing of restrictions, we should still act with caution to help protect one another and curb the rate of infections,” he added.
The study showed that the highest infection prevalence was found in young people aged 13-24 years at 1.56 per cent or 1 in 65 infected, while the lowest was in people aged above 75 years at 0.17 per cent. Women had a lower risk of testing positive than men (0.55 per cent vs 0.71 per cent).
Previous study data showed that the link between infections, hospitalisations and deaths had been weakening since February.
However, since mid-April, the trends between infections and hospitalisations were growing closer together again, although to a smaller extent for deaths. This could reflect the switch from Alpha to Delta, and a changing mix (towards younger and unvaccinated people) of hospitalised cases, the researchers said.
