New research has found that England’s coronavirus epidemic is stable overall but patterns of infection are different across age groups and regions.
The findings from the Imperial-led REACT-1 study, a major ongoing coronavirus monitoring programme, are based on home swab tests taken by 100,000 people between 9 and 27 September. The data show that 1 in 120 people had the virus during this period, or 0.83% of the population.
The overall reproduction number (R) was found to be around 1 (1.03), meaning that on average one infected person would pass the virus on to one other person. The epidemic overall is therefore neither growing nor shrinking.
"These trends reinforce how important it is for children aged 12 and above to get vaccinated." Prof Paul Elliott School of Public Health, Imperial
However there was wide variation across different age groups. Infections were found to be rising in those aged 17 and under, with an R of 1.18, while a decrease was found in people aged 18-54 with an R of 0.81.
The highest number of infections were found in school-aged children, with 1 in 43 5-12-year-olds infected (2.32%), and 1 in 39 13-17-year-olds (2.55%).
Professor Paul Elliott, director of the REACT programme from Imperial’s School of Public Health, said: “Our latest data show that infections are high and rising in school-aged children. Households with children also had a higher prevalence of infection, suggesting that children may be passing on the virus to those that they live with.
“These trends reinforce how important it is for children aged 12 and above to get vaccinated and help curb the spread of infection, and minimise disruption to education.”
These findings from the ongoing REal-time Assessment of Community Transmission (REACT-1) programme, carried out in partnership with Ipsos MORI and commissioned by the UK Health Security Agency, are available here in a pre-print report and will be submitted for peer-review. Data are continually reported to the government to inform decision-making.
Regional coronavirus trends
For this latest round of the REACT study, 100,527 people swabbed themselves at home and their samples were analysed by PCR testing. 764 of these were positive, giving an overall weighted prevalence of 0.83%. Weighting is where the researchers make adjustments to their calculations to ensure the sample reflects England’s population.
Although this is higher than the study’s previous findings in July, when 0.63% (1 in 158) were infected, the findings can’t be directly compared as the method of sample handling changed for this round and future rounds. Previously, dry swabs were collected and transported chilled. The new, simpler method stores the swabs in saline solution while transported, which aren’t kept refrigerated.
Looking at trends across the country, the lowest prevalence of infection was found in the South East at 0.57%, while the highest was found in Yorkshire and the Humber at 1.25%. The researchers also identified evidence of growth in London and East Midlands where R was above 1 (1.59 and 1.36, respectively).
Patterns of infection
Differences in rates of infection were also found across demographic groups and by vaccination status.
- People of Black ethnicity had a higher burden of infection than White people (1.41%, 0.78%).
- Prevalence was higher in larger households, ranging from 0.33% in single-person homes to 1.75% in those with 6 or more occupants.
- Infections were more than twice as high in people who reported they were unvaccinated (1.73%) compared to those who had received two doses (0.56%).
The researchers also estimated the effectiveness of vaccination at protecting against infection. By combining data from this round of testing with the previous round, they estimated that vaccination effectiveness for all participants and vaccines combined was 62.8%, when round, age, sex, deprivation, region and ethnicity were accounted for.
Prevalence of infection was found to be higher in those who received their second dose of vaccine 3-6 months after taking their swab, compared to those whose second dose was within 3 months of their swab (0.55% and 0.35%, respectively). For people who had their second dose more than 6 months before taking part in the study, the prevalence was uncertain because there were smaller numbers in this group.
By vaccine type, this study estimated vaccine effectiveness against infection was 44.8% for AstraZeneca and 71.3% for Pfizer/BioNTech. Among only people who had symptomatic infection, effectiveness against infection was 66.4% overall. The study did not look at protection against hospitalisation and death, which both vaccines have been shown to be highly effective at preventing.
Professor Christl Donnelly, Professor of Statistical Epidemiology at Imperial, said: “We found more breakthrough SARS-CoV-2 infections among those who received their second vaccine dose between 3 and 6 months ago than those whose second dose was less than 3 months ago. However, booster doses offer the prospect of increased protection lowering population infection levels.”
Dr Jenny Harries, Chief Executive of the UK Health Security Agency, said: “These data demonstrate that while our vaccination programme continues to make a huge difference, the pandemic is not over. As we move towards winter, it is as important as ever that we continue to act responsibly in order to avoid transmission.
“While cases remain high, the vaccination programme is ensuring that this does not translate to a similarly high number of hospitalisations and deaths. We are urging everyone who is eligible to come forward for vaccination. It is the best way to reduce transmission and protect ourselves and those we love.”
"I urge anyone who needs one to get a jab as soon as possible – it’s vital to keep you and your family safe this winter." Sajid Javid Health and Social Care Secretary
Health and Social Care Secretary Sajid Javid said: “The phenomenal progress of our vaccination programme has built a strong wall of defence across the country, allowing us to live safely with this virus.
“These findings show how important it is for young people to get the jab to protect them from COVID-19, and for those eligible to get their booster vaccine to prolong their existing protection. I urge anyone who needs one to get a jab as soon as possible – it’s vital to keep you and your family safe this winter.”
Monitoring the COVID-19 epidemic
The REACT-1 study is tracking current coronavirus infections in the community by testing more than 100,000 randomly selected people each month over roughly a two-week period. The study recruits new people each month to help ensure the sample represents the wider population and offers a high-resolution snapshot of the situation across a particular time period.
This is different from the ONS COVID-19 Infection Survey which runs continuously and samples the same people over time to understand household transmission. Because the studies use different methods, this means that sometimes they report different figures.
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