Long COVID prevalence estimates vary widely owing to inconsistent definitions and heterogeneous methods of analysis.
In a systematic review and meta-analysis, approximately 63% of patients reported at least one symptom at 30 days after symptom onset/hospitalization, with 71% reporting at least one symptom after 60 days, and 46% at 90 days or more.[14]Fernández-de-Las-Peñas C, Palacios-Ceña D, Gómez-Mayordomo V, et al. Prevalence of post-COVID-19 symptoms in hospitalized and non-hospitalized COVID-19 survivors: a systematic review and meta-analysis. Eur J Intern Med. 2021 Oct;92:55-70.
https://www.doi.org/10.1016/j.ejim.2021.06.009
http://www.ncbi.nlm.nih.gov/pubmed/34167876?tool=bestpractice.com
In another systematic review, 54% of patients reported at least one symptom at 1 month, 55% of patients reported at least one symptom at 2 to 5 months, and 54% of patients reported at least one symptom at 6 months or longer.[15]Groff D, Sun A, Ssentongo AE, et al. Short-term and long-term rates of postacute Ssequelae of SARS-CoV-2 infection: a systematic review. JAMA Netw Open. 2021 Oct 1;4(10):e2128568.
https://www.doi.org/10.1001/jamanetworkopen.2021.28568
http://www.ncbi.nlm.nih.gov/pubmed/34643720?tool=bestpractice.com
However, some studies report much lower rates of continuing symptoms after 12 weeks (2.3% to 3%).[16]Sudre CH, Murray B, Varsavsky T, et al. Attributes and predictors of long COVID. Nat Med. 2021 Apr;27(4):626-31.
https://www.doi.org/10.1038/s41591-021-01292-y
http://www.ncbi.nlm.nih.gov/pubmed/33692530?tool=bestpractice.com
[17]Office for National Statistics. 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. September 2021 [internet publication].
https://www.ons.gov.uk/peoplepopulationandcommunity/healthandsocialcare/conditionsanddiseases/articles/technicalarticleupdatedestimatesoftheprevalenceofpostacutesymptomsamongpeoplewithcoronaviruscovid19intheuk/26april2020to1august2021
A study that corrected for individual symptoms present before coronavirus disease 2019 (COVID-19) and the symptom dynamics in the population without severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) infection found that 12.7% of patients are likely to experience long-term symptoms at 90 to 150 days after infection.[18]Ballering AV, van Zon SKR, Olde Hartman TC, et al. Persistence of somatic symptoms after COVID-19 in the Netherlands: an observational cohort study. Lancet. 2022 Aug 6;400(10350):452-61.
https://www.doi.org/10.1016/S0140-6736(22)01214-4
http://www.ncbi.nlm.nih.gov/pubmed/35934007?tool=bestpractice.com
Persistent symptoms have been reported up to 12 months after discharge, but most people had a good and functional recovery during 1-year follow-up.[19]Wu X, Liu X, Zhou Y, et al. 3-month, 6-month, 9-month, and 12-month respiratory outcomes in patients following COVID-19-related hospitalisation: a prospective study. Lancet Respir Med. 2021 Jul;9(7):747-54.
https://www.doi.org/10.1016/S2213-2600(21)00174-0
http://www.ncbi.nlm.nih.gov/pubmed/33964245?tool=bestpractice.com
[20]Huang L, Yao Q, Gu X, et al. 1-year outcomes in hospital survivors with COVID-19: a longitudinal cohort study. Lancet. 2021 Aug 28;398(10302):747-58.
https://www.doi.org/10.1016/S0140-6736(21)01755-4
http://www.ncbi.nlm.nih.gov/pubmed/34454673?tool=bestpractice.com
Persistent symptoms have also been reported at 2-year follow-up in a significant number of patients, with fatigue and muscle weakness being the most frequent.[21]Huang L, Li X, Gu X, et al. Health outcomes in people 2 years after surviving hospitalisation with COVID-19: a longitudinal cohort study. Lancet Respir Med. 2022 Sep;10(9):863-76.
https://www.doi.org/10.1016/S2213-2600(22)00126-6
http://www.ncbi.nlm.nih.gov/pubmed/35568052?tool=bestpractice.com
Prolonged illness can occur among young adults with no underlying comorbidities, and in patients who had mild disease.[22]Subramanian A, Nirantharakumar K, Hughes S, et al. Symptoms and risk factors for long COVID in non-hospitalized adults. Nat Med. 2022 Aug;28(8):1706-14.
https://www.doi.org/10.1038/s41591-022-01909-w
http://www.ncbi.nlm.nih.gov/pubmed/35879616?tool=bestpractice.com
[23]Augustin M, Schommers P, Stecher M, et al. Post-COVID syndrome in non-hospitalised patients with COVID-19: a longitudinal prospective cohort study. Lancet Reg Health Eur. 2021 Jul;6:100122.
https://www.doi.org/10.1016/j.lanepe.2021.100122
http://www.ncbi.nlm.nih.gov/pubmed/34027514?tool=bestpractice.com
Approximately 12% to 15% of patients who had mild symptoms still had symptoms up to 8 months later.[24]Havervall S, Rosell A, Phillipson M, et al. Symptoms and functional impairment assessed 8 months after mild COVID-19 among health care workers. JAMA. 2021 May 18;325(19):2015-6.
https://www.doi.org/10.1001/jama.2021.5612
http://www.ncbi.nlm.nih.gov/pubmed/33825846?tool=bestpractice.com
The number of symptoms at follow-up was associated with the symptom load during the acute phase of infection and the number of comorbidities in non-hospitalized patients.[25]Stavem K, Ghanima W, Olsen MK, et al. Persistent symptoms 1.5-6 months after COVID-19 in non-hospitalised subjects: a population-based cohort study. Thorax. 2021 Apr;76(4):405-7.
https://www.doi.org/10.1136/thoraxjnl-2020-216377
http://www.ncbi.nlm.nih.gov/pubmed/33273028?tool=bestpractice.com
Asymptomatic infection is associated with a lower risk of developing long-term sequelae.[26]Ma Y, Deng J, Liu Q, et al. Long-term consequences of asymptomatic SARS-CoV-2 infection: a systematic review and meta-analysis. Int J Environ Res Public Health. 2023 Jan 16;20(2):1613.
https://www.doi.org/10.3390/ijerph20021613
http://www.ncbi.nlm.nih.gov/pubmed/36674367?tool=bestpractice.com
Persistent symptoms have been reported in pregnant women and children. A meta-analysis found the prevalence was 25% in children and adolescents, with the most prevalent symptoms being mood symptoms, fatigue, and sleep disorders.[27]Lopez-Leon S, Wegman-Ostrosky T, Ayuzo Del Valle NC, et al. Long-COVID in children and adolescents: a systematic review and meta-analyses. Sci Rep. 2022 Jun 23;12(1):9950.
https://www.doi.org/10.1038/s41598-022-13495-5
http://www.ncbi.nlm.nih.gov/pubmed/35739136?tool=bestpractice.com
However, evidence in children is limited, heterogeneous, and based on low-quality studies.[28]Pellegrino R, Chiappini E, Licari A, et al. Prevalence and clinical presentation of long COVID in children: a systematic review. Eur J Pediatr. 2022 Dec;181(12):3995-4009.
https://www.ncbi.nlm.nih.gov/pmc/articles/PMC9476461
http://www.ncbi.nlm.nih.gov/pubmed/36107254?tool=bestpractice.com
Low-certainty evidence suggests that vaccination before SARS-CoV-2 infection may reduce the risk of long COVID. The impact of vaccination in people with existing long COVID is inconsistent.[29]Notarte KI, Catahay JA, Velasco JV, et al. Impact of COVID-19 vaccination on the risk of developing long-COVID and on existing long-COVID symptoms: a systematic review. EClinicalMedicine. 2022 Nov;53:101624.
https://www.doi.org/10.1016/j.eclinm.2022.101624
http://www.ncbi.nlm.nih.gov/pubmed/36051247?tool=bestpractice.com
A meta-analysis of 54 studies and two medical record databases from 22 countries, which included data for 1.2 million individuals, estimated that 6.2% of people who had symptomatic COVID-19 experienced at least one of the following after 3 months: persistent fatigue with pain or mood swings (3.2%), cognitive problems (2.2%), or ongoing respiratory problems (3.7%).[10]Global Burden of Disease Long COVID Collaborators, Wulf Hanson S, Abbafati C, et al. Estimated global proportions of individuals with persistent fatigue, cognitive, and respiratory symptom clusters following symptomatic COVID-19 in 2020 and 2021. JAMA. 2022 Oct 25;328(16):1604-15.
https://www.doi.org/10.1001/jama.2022.18931
http://www.ncbi.nlm.nih.gov/pubmed/36215063?tool=bestpractice.com
This analysis did not include patients who were infected with the Omicron variant. The risk of developing long COVID may be lower among people infected with the Omicron variant compared with those infected with previous variants.[30]Antonelli M, Pujol JC, Spector TD, et al. Risk of long COVID associated with delta versus omicron variants of SARS-CoV-2. Lancet. 2022 Jun 18;399(10343):2263-4.
https://www.doi.org/10.1016/S0140-6736(22)00941-2
http://www.ncbi.nlm.nih.gov/pubmed/35717982?tool=bestpractice.com
[31]Fernández-de-Las-Peñas C, Notarte KI, Peligro PJ, et al. Long-COVID symptoms in individuals infected with different SARS-CoV-2 variants of concern: a systematic review of the literature. Viruses. 2022 Nov 25;14(12):2629.
https://www.doi.org/10.3390/v14122629
http://www.ncbi.nlm.nih.gov/pubmed/36560633?tool=bestpractice.com