Impact of Delta on viral burden and vaccine effectiveness against new SARS-CoV-2 infections in the UK
N = 384,543
Households, 221,909
Obtaining two vaccine doses remains the most effective way to ensure protection against Delta
With Delta, Pfizer-BioNTech and Oxford-AstraZeneca vaccines still offer good protection against new infections
but effectiveness is reduced compared with Alpha
However, Delta infections after two vaccine doses had similar peak levels of virus to those in unvaccinated people
(with the Alpha variant, peak virus levels in those infected post-vaccination were much lower)
Two doses of either vaccine still provided at least the same level of protection as having had COVID-19 through natural infection
People who had been vaccinated after already being infected with COVID-19 had even more protection than vaccinated individuals who had not had COVID-19 before
Two doses of Pfizer-BioNTech have greater initial effectiveness against new COVID-19 infections
but this declines faster compared with two doses of Oxford-AstraZeneca
After four to five months, effectiveness of these two vaccines similar
however, long-term effects need to be studied
The time between doses does not affect effectiveness in preventing new infections
Younger people have even more protection from vaccination than older people
UK, third shots
Prof Peter Openshaw
New and Emerging Respiratory Virus Threats Advisory Group (NERVTAG
We can’t just look at the antibody levels and think that that equates to levels of protection
It still seems that you get a lot of protection from these vaccines, even if the antibody levels have drifted down to some sort of stable level
