“Long COVID” or “ongoing COVID” are terms given to those who remain ill with COVID-19 for a period of time longer than four weeks.
The National Institute of Health Care Excellence (NICE) in the United Kingdom describes two clinical definitions for long COVID:
- ongoing symptomatic COVID-19 — signs and symptoms of COVID-19 from 4 to 12 weeks; and
- post-COVID-19 syndrome — signs and symptoms that develop during or after an infection consistent with COVID-19, continue for more than 12 weeks and are not explained by an alternative diagnosis.
The Centers for Disease Control and Prevention (CDC) in the United States refer to “post-COVID conditions” as a wide range of new, returning, or ongoing health problems people can experience more than four weeks after first being infected with the virus that causes COVID-19.
What evidence is there for levels of long COVID in the UK?
Long COVID is an emerging phenomenon that is not yet fully understood.
The incidence of long COVID in the UK has been tracked and measured in two ways:
- counting the number of people presenting to GPs with long COVID symptoms; and
- surveying a sample of the population, asking them to self-report long COVID symptoms.
1. Counting the number of people presenting to a GP with long COVID symptoms
The primary care records for people registered with GPs in England were analysed through the OpenSAFELY tool to detect incidences of the 15 SNOMED CT codes (introduced in November 2020) used to indicate diagnosis, referral, and assessment related to long COVID.
As of 25 April 2021, analysis of the medical records of 58.0m people in England found 23,273 patients with codes indicating a long COVID diagnosis. While equivalent to 53.7 instances of long COVID per 100,000 people (or 0.05% of the English population), the study’s authors suggest that this could be a substantial underestimate:
Long COVID coding in primary care is low compared with early reports of long COVID prevalence. This may reflect under-coding, sub-optimal communication of clinical terms, under-diagnosis, a true low prevalence of long COVID diagnosed by clinicians, or a combination of factors.
2. Surveying a sample of the population, asking them to self report long COVID symptoms
The Office National Statistics’ COVID-19 Infection Survey tracks the incidence of COVID-19 in the UK, by conducting tests on a representative sample of the population. It also asks participants the following question regarding long COVID:
Would you describe yourself as having “long COVID”, that is, you are still experiencing symptoms more than 4 weeks after you first had COVID-19, that are not explained by something else?
By 15 May 2021, 233,760 households and 499,298 individuals were registered for the survey (approximately 0.75% of the UK population).
The survey includes 6,578 households and 14,121 individuals in Northern Ireland (again, approximately 0.75% of the total population).
At the time of writing, the most up to date ONS survey data on long COVID covers the four-week period up to 6 March 2021. The table below summarises the estimated people in the UK and the four nations suffering with long COVID. Two figures are calculated: people who report long COVID of any duration; and those who report long COVID of 12 or more weeks after getting COVID-19.
|Region||Incidence of long COVID per 100,000 people (any duration)||Incidence of long COVID per 100,000 people (people with confirmed or suspected COVID-19 at least 12 weeks previously)|
The latest 12-week figures still only include people who became ill with confirmed or suspected COVID in 2020.
The ONS survey data suggests that between 1% and 2% of the population were ill with long COVID as of 6 March 2021, with levels in Northern Ireland slightly lower than the UK average.
The ONS figures of self-reported long COVID are significantly higher than the analysis of English GP records referring to long COVID.
The prevalence of long COVID symptoms
One in five people could show “ongoing symptomatic COVID-19” according to the ONS survey data, which suggest that 21.0% of people who tested positive for COVID-19 subsequently went on to develop long COVID symptoms, defined as having any symptoms five weeks after their assumed infection date (18.7% of men, 23.0% of women).
ONS found that the most commonly reported symptoms of long COVID were: fatigue (found among 11.8% of people who tested positive for COVID-19 five weeks later), cough (10.9%), and headache (10.1%).
Long COVID symptoms five weeks after presumed infection were most common in the 35–49 year old age group (25.6%) and least common in children under 12 years of age (9.8%).
More than 1 in 8 people could show “post-COVID-19 syndrome” according to the ONS survey, which suggest that 13.7% of people who tested positive for COVID-19 still had symptoms 12 weeks after the presumed date of infection (12.7% of men, 14.7% of women).
Twelve weeks after infection, fatigue was still the most common symptom (8.3%), followed by headache (7.2%) and cough (7.0%). Long COVID symptoms 12 weeks after presumed infection were most common in the 25–34 year old age group (18.2%) and least common in children under 12 years of age (7.4%).
The study of long COVID is only in its infancy, and the potential impact and duration of long COVID is still uncertain. Studies suggest that long COVID symptoms may be eased by vaccination against COVID-19, and research in this area is ongoing.
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