Britain is no longer in a pandemic, experts have said, as new data showed the vaccination programme is reducing symptomatic COVID infections by up to 90%. The Guardian reports that in the first large real-world study of the impact of vaccination on the general population, researchers found that the rollout is having a major impact on cutting both symptomatic and asymptomatic cases.
Sarah Walker, professor of medical statistics and epidemiology at the University of Oxford and chief investigator on the Office for National Statistics COVID-19 Infection Survey, said that Britain had “moved from a pandemic to an endemic situation” where the virus is circulating at a low, largely controllable level in the community.
Data from the COVID-19 Infection Survey, is the first to show the impact of vaccination on antibody responses and new infections in a large group of adults from the general population aged 16 years and older.
Two studies, released as pre-prints, focused on the protection from infection provided by COVID-19 vaccines. Researchers analysed 1,610,562 test results from nose and throat swabs taken from 373,402 study participants between 1 December 2020 and 3 April 2021. 21 days after a single dose of either Oxford-AstraZeneca or Pfizer-BioNTech vaccines (with no second dose), the rates of all new COVID-19 infections had dropped by 65%, symptomatic infections by 72% and infections without reported symptoms by 57%.
Reductions in infections and symptomatic infections were even greater after a second dose (70% and 90% respectively), and were similar to effects in those who had previously been infected with COVID-19 naturally. Vaccines were effective against variants compatible with the Kent strain (B.1.1.7). Benefits from vaccines in reducing new infections were similar in older individuals over 75 years and under 75 years, and in those reporting long-term health conditions and not reporting them.
Dr Koen Pouwels, senior researcher in Oxford University’s Nuffield department of population health, says: “The protection from new infections gained from a single dose supports the decision to extend the time between first and second doses to 12 weeks to maximise initial vaccination coverage and reduce hospitalisations and deaths.
“However, the fact that we saw smaller reductions in asymptomatic infections than infections with symptoms highlights the potential for vaccinated individuals to get COVID-19 again, and for limited ongoing transmission from vaccinated individuals, even if this is at a lower rate. This emphasises the need for everyone to continue to follow guidelines to reduce transmission risk, for example through social distancing and masks.”
The second study compared how antibody levels changed after a single dose of either Oxford-AstraZeneca or Pfizer-BioNTech vaccines, or two doses of the Pfizer-BioNTech vaccine (generally given 21-42 days apart). In individuals who had not had COVID-19 before, antibody responses to a single dose of either vaccine were lower in older individuals, especially over 60 years. Antibody responses to two Pfizer-BioNTech doses were high across all ages, particularly increasing responses in older people to reach similar levels to those receiving a single dose after prior infection.
Antibody levels rose more slowly and to a lower level with a single dose of Oxford-AstraZeneca vs Pfizer-BioNTech, but then dropped more quickly with a single Pfizer-BioNTech dose to similar levels as a single dose of Oxford-AstraZeneca, particularly at older ages. However, although the size of the immune response differed, there was no group of individuals who didn’t respond at all to either vaccine.
David Eyre, associate professor at the Big Data Institute at the University of Oxford, says: “In older individuals, two vaccine doses are as effective as prior natural infection at generating antibodies to the SARS-CoV-2 virus that causes COVID-19 – in younger individuals a single dose achieves the same level of response. Our findings highlight the importance of individuals getting the second vaccine dose for increased protection.”
Walker says: “Without large community surveys such as ours, it is impossible to estimate the impact of vaccination on infections without symptoms – these have the potential to keep the epidemic going, particularly if people who have been vaccinated mistakenly think they cannot catch COVID-19. However, these studies show that vaccination and previous infection both protect against getting infected again.
“We don’t yet know exactly how much of an antibody response, and for how long, is needed to protect people against getting COVID-19 in the long-term – but over the next year, information from the survey should help us to answer these questions. We are very grateful to all our participants for giving up their time to help us.:
The study will continue monitoring the pandemic in the UK on a weekly basis to look for early warning signs of rising infection rates in different regions, sub-regions, and demographic groups, and to continue to compare the effectiveness of different vaccines and to monitor the impact of immunity on protection against COVID-19.