By Marija Djekic-Ivankovic
Long COVID is an emerging phenomenon that is not yet fully understood or well defined. This technical article, recently released by UK Office for National Statistics, presents a range of prevalence estimates regarding the number of people who experience symptoms beyond the acute phase of COVID-19 infection, commonly referred to as “long COVID”. Researchers indicate that long COVID may affect 3% to 12% of people with COVID-19 with estimates going as high as 7% to 18% when using a different estimation methodology. The variability in estimates is likely due to a lack of consensus in capturing and defining the full range of long COVID illnesses.
- By using three different approaches (see details below) and data gathered between April 26th, 2020, and August 1st, 2021, researchers found that between 3% and 12% of people with COVID-19 had symptoms 12 weeks after the initial infection. This translates to a prevalence of 7% to 18% when considering only those who were symptomatic during the acute phase of infection (some people have reported no or few symptoms during their COVID infection yet still have long COVID symptoms).
- Most people infected with coronavirus (88% to 97%) are unlikely to experience symptoms beyond the first 12 weeks. However, for those who do go on to experience long-term symptoms, the effects can be debilitating. The most recent United Kingdom (UK) population-level estimates suggest that 643,000 people in private households in the UK could be experiencing activity-limiting long COVID symptoms.
- Using a sample of over 20,000 participants infected with SARS-CoV-2, researchers concluded that long COVID symptom prevalence was highest in females, adults aged 50 to 69 years, people with a pre-existing health condition, and those with signs of high viral load at the time of infection (determined by severity of symptoms).
Three approaches used:
- This approach defined prevalence as the presence of any of the listed symptoms at any point in time after infection. Among infected participants, 5.0% reported at least one of the 12 most common symptoms 12 to 16 weeks after infection. However, prevalence was 3.4% in a control group of non-infected participants, demonstrating the relative commonness of these symptoms in the population at any given time.
- This approach captured prevalence as the presence of continuous symptoms after infection. Among infected participants, 3.0% experienced at least one of the 12 most common symptoms for a continuous period of at least 12 weeks after infection, compared with 0.5% in the control group. The corresponding prevalence estimate when considering only participants who were symptomatic at the acute phase of infection was 6.7%.
- This third approach measures prevalence through self-reported presence of long COVID. An estimated 11.7% of study participants described themselves as experiencing long COVID 12 weeks after infection based on self-classification, a percentage that increased to 17.7% when only symptomatic participants were included. They could therefore meet the clinical case definition of long-COVID. Fewer people, 7.5%, considered their long COVID symptoms to limit to day-to-day activities, yet this percentage increased to 11.8% when considering only participants who were symptomatic at the acute phase of infection.
Ayoubkhani D, Pawelek P, Gaughan C. Technical article: Updated estimates of the prevalence of post-acute symptoms among people with coronavirus (COVID-19) in the UK: 26 April 2020 to 1 August 2021. UK Office for National Statistics. Released: 16 September 2021