Tag: covid variants

The original strain of SARS-CoV-2, the Delta variant, and the Omicron variant infect microglia efficiently, in contrast to their inability to infect neurons: Analysis using 2D and 3D cultures

Highlights:

  • None of the SARS-CoV-2 original, delta, or omicron strains can infect neurons.
  • The SARS-CoV-2 original, delta, and omicron strains can infect microglia.
  • The CNS cells differentiated from hiPSCs are useful to investigate the infectivity of the virus.

Abstract:

COVID-19 causes neurological damage, systemic inflammation, and immune cell abnormalities. COVID-19-induced neurological impairment may be caused by severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2), which directly infects cells of the central nervous system (CNS) and exerts toxic effects. Furthermore, SARS-CoV-2 mutations occur constantly, and it is not well understood how the infectivity of the virus to cells of the CNS changes as the virus mutates.

Few studies have examined whether the infectivity of cells of CNS – neural stem/progenitor cells (NS/PCs), neurons, astrocytes, and microglia – varies among SARS-CoV-2 mutant strains. In this study, therefore, we investigated whether SARS-CoV-2 mutations increase infectivity to CNS cells, including microglia.

Since it was essential to demonstrate the infectivity of the virus to CNS cells in vitro using human cells, we generated cortical neurons, astrocytes, and microglia from human induced pluripotent stem cells (hiPSCs). We added pseudotyped lentiviruses of SARS-CoV-2 to each type of cells, and then we examined their infectivity. We prepared three pseudotyped lentiviruses expressing the S protein of the original strain (the first SARS-CoV-2 discovered in the world), the Delta variant, and the Omicron variant on their envelopes and analyzed differences of their ability to infect CNS cells. We also generated brain organoids and investigated the infectivity of each virus.

The viruses did not infect cortical neurons, astrocytes, or NS/PCs, but microglia were infected by the original, Delta, and Omicron pseudotyped viruses. In addition, DPP4 and CD147, potential core receptors of SARS-CoV-2, were highly expressed in the infected microglia, while DPP4 expression was deficient in cortical neurons, astrocytes, and NS/PCs.

Our results suggest that DPP4, which is also a receptor for Middle East respiratory syndrome-coronavirus (MERS-CoV), may play an essential role in the CNS. Our study is applicable to the validation of the infectivity of viruses that cause various infectious diseases in CNS cells, which are difficult to sample from humans.

Source: Kase Y, Sonn I, Goto M, Murakami R, Sato T, Okano H. The original strain of SARS-CoV-2, the Delta variant, and the Omicron variant infect microglia efficiently, in contrast to their inability to infect neurons: Analysis using 2D and 3D cultures. Exp Neurol. 2023 Mar 11;363:114379. doi: 10.1016/j.expneurol.2023.114379. Epub ahead of print. PMID: 36914084; PMCID: PMC10008041. https://www.sciencedirect.com/science/article/pii/S0014488623000638?via%3Dihub (Full text)

COVID-19 long-term sequelae: Omicron versus Alpha and Delta variants

Abstract:

Background: The study aimed to assess the association between three predominant SARS-CoV-2 variants (Alpha, Delta, and Omicron) and the risk of developing long COVID (persistence of physical, medical, and cognitive symptoms more than 4 weeks after infection), post-COVID-19 syndrome (symptoms extending beyond 12 weeks), and viral persistence (testing positive beyond 4 weeks despite clinical resolution).

Methods: Retrospective study of 325 patients hospitalized for COVID-19 with genomic sequencing information. For each SARS-CoV-2 variant, sample characteristics, frequency of symptoms, and long-term sequelae were compared using Chi-squared test, Fisher’s exact test, Kruskal-Wallis test, and Dunn’s test as appropriate. Odds ratios (OR) were calculated using logistic regression models to assess the association of risk factors and sequelae.

Results: The adjusted model showed that the Omicron (vs Alpha) variant (OR, 0.30; 95% CI0.16-0.56), admission to ICU (OR, 1.14; 95% CI 1.05-1.23), and being treated with antiviral or immunomodulatory drugs (OR, 2.01; 95% CI 1.23-3.27) predicted long COVID and post-COVID-19 syndrome. Viral persistence showed no difference between variants.

Conclusions: The Omicron variant was associated with significantly lower odds of developing long-term sequelae from COVID-19 compared with previous variants, while severity of illness indicators increased the risk. Vaccination status, age, sex, and comorbidities were not found to predict sequelae development. This information has implications for both health managers and clinicians when deciding on the appropriate clinical management and subsequent outpatient follow-up of these patients. More studies with non-hospitalized patients are still necessary.

Source: Hernández-Aceituno A, García-Hernández A, Larumbe-Zabala E. COVID-19 long-term sequelae: Omicron versus Alpha and Delta variants. Infect Dis Now. 2023 Feb 27:104688. doi: 10.1016/j.idnow.2023.104688. Epub ahead of print. PMID: 36858287; PMCID: PMC9970656. https://www.ncbi.nlm.nih.gov/pmc/articles/PMC9970656/ (Full text)

Outpatient Treatment of COVID-19 and the Development of Long COVID Over 10 Months: A Multi-Center, Quadruple-Blind, Parallel Group Randomized Phase 3 Trial

Abstract:

Background: Post-acute sequelae of COVID, termed “Long COVID”, is an emerging chronic illness potentially affecting ~10% of those with COVID-19. We sought to determine if outpatient treatment with metformin, ivermectin, or fluvoxamine could prevent Long COVID.

Methods: COVID-OUT (NCT04510194) was a decentralized, multi-site trial in the United States testing three medications (metformin, ivermectin, fluvoxamine) using a 2×3 parallel treatment factorial randomized assignment to efficiently share placebo controls. Participants, investigators, care providers, and outcomes assessors were masked to randomized treatment assignment. Inclusion criteria included: age 30 to 85 years with overweight or obesity, symptoms <7 days, enrolled within <=3 days of documented SARS-CoV-2 infection. Long COVID diagnosis from a medical provider was a pre-specified secondary outcome assessed by monthly surveys through 300 days after randomization and confirmed in medical records.

Findings: Of 1323 randomized trial participants, 1125 consented for long-term follow up, and 95.1% completed >9 months of follow up. The median age was 45 years (IQR, 37 to 54), and 56% were female (7% pregnant). The median BMI was 30 kg/m2 (IQR, 27 to 34). Overall, 8.4% reported a medical provider diagnosed them with Long COVID; cumulative incidence: 6.3% with metformin and 10.6% with matched placebo. The hazard ratio (HR) for metformin preventing Long COVID was 0.58 (95%CI, 0.38 to 0.88; P=0·009) versus placebo. The metformin effect was consistent across subgroups, including viral variants. When metformin was started within <4 days of symptom onset, the HR for Long COVID was 0.37 (95%CI, 0.15 to 0.95).  No statistical difference in Long COVID occurred in those randomized to either ivermectin (HR=0.99; 95%CI, 0.59 to 1.64) or fluvoxamine (HR=1.36; 95%CI, 0.78 to 2.34).

Interpretations: A 42% relative decrease and 4.3% absolute decrease in the Long COVID incidence occurred in participants who received early outpatient COVID-19 treatment with metformin compared to exact-matching placebo.

Source: Bramante, Carolyn and Buse, John B. and Liebovitz, David and Nicklas, Jacinda and Puskarich, Michael and Cohen, Kenneth R. and Belani, Hrishikesh and Anderson, Blake and Huling, Jared D. and Thompson, Jennifer and Pullen, Matthew and Wirtz, Esteban Lemus and Siegel, Lianne and Proper, Jennifer and Odde, David J. and Klatt, Nichole and Sherwood, Nancy E. and Lindberg, Sarah and Karger, Amy B. and Beckman, Kenneth B. and Erickson, Spencer and Fenno, Sarah and Hartman, Katrina and Rose, Michael and Mehta, Tanvi and Patel, Barkha and Griffiths, Gwendolyn and Bhat, Neeta and Murray, Thomas A. and Boulware, David R., Outpatient Treatment of COVID-19 and the Development of Long COVID Over 10 Months: A Multi-Center, Quadruple-Blind, Parallel Group Randomized Phase 3 Trial. Available at SSRN: https://ssrn.com/abstract=4375620 or http://dx.doi.org/10.2139/ssrn.4375620

Blood-brain barrier penetration of non-replicating SARS-CoV-2 and S1 variants of concern induce neuroinflammation which is accentuated in a mouse model of Alzheimer’s disease

Highlights:

• Two models of SARS-CoV-2 and all S1 protein Variants of Concern readily cross the BBB.
• The SARS-CoV-2 pseudovirus is taken up by microglia and induce neuroinflammation.
• The S1-induced neuroinflammation is exacerbated in a mouse model of Alzheimer’s disease.

Abstract:

COVID-19 and especially Long COVID are associated with severe CNS symptoms and may place persons at risk to develop long-term cognitive impairments. Here, we show that two non-infective models of SARS-CoV-2 can cross the blood–brain barrier (BBB) and induce neuroinflammation, a major mechanism underpinning CNS and cognitive impairments, even in the absence of productive infection. The viral models cross the BBB by the mechanism of adsorptive transcytosis with the sugar N-acetylglucosamine being key. The delta and omicron variants cross the BB B faster than the other variants of concern, with peripheral tissue uptake rates also differing for the variants. Neuroinflammation induced by icv injection of S1 protein was greatly enhanced in young and especially in aged SAMP8 mice, a model of Alzheimer’s disease, whereas sex and obesity had little effect.

Source: Erickson MA, Logsdon AF, Rhea EM, Hansen KM, Holden SJ, Banks WA, Smith JL, German C, Farr SA, Morley JE, Weaver RR, Hirsch AJ, Kovac A, Kontsekova E, Baumann KK, Omer MA, Raber J. Blood-brain barrier penetration of non-replicating SARS-CoV-2 and S1 variants of concern induce neuroinflammation which is accentuated in a mouse model of Alzheimer’s disease. Brain Behav Immun. 2023 Jan 20;109:251-268. doi: 10.1016/j.bbi.2023.01.010. Epub ahead of print. PMID: 36682515; PMCID: PMC9867649. https://www.ncbi.nlm.nih.gov/pmc/articles/PMC9867649/ (Full text)

Long-COVID Rates Vary Throughout the SARS-CoV-2 Pandemic

Abstract:

The infection with Severe Acute Respiratory Syndrome Coronavirus-2 (SARS-CoV-2) frequently causes a broad range of long-lasting symptoms. This condition, termed long-COVID, influences everyday life of affected individuals in many ways and causes a high economic burden. There is urgent need to obtain better understanding of the risk factors that contribute to the development of long-COVID.

Aim of this study was to investigate the long-COVID rate of supposedly healthy adults during different phases of the pandemic. Therefore, 71,670 blood donations were screened for SARS-CoV-2 total anti-N antibodies between 5 th June 2020 and 30 th November 2022. 351 individuals could be recruited for our study to monitor long-COVID symptoms and their duration. Despite immense worldwide efforts to stop virus dissemination, our data reveal a constantly rising SARS-CoV-2 anti-N seroprevalence rate in Salzburg, Austria, peaking at 84.9% in October 2022.

In addition, our data demonstrate varying rates of long-COVID in the course of the pandemic. While long-COVID rates were about 20% for the time span between March 2020 and August 2021, long-COVID was reported by 12% for infections from September 2021 to August 2022. This could be attributed to different virus variants, but also to increasing vaccination rates. We further found that long-COVID symptoms decline over time: while 18% of our study participants described persisting symptoms 3 months after the seropositive blood donation, 14% reported persisting symptoms 9 months afterwards and 3% after 18 months.

In conclusion, our data reveal that long-COVID symptoms may persist for more than a year after a SARS-CoV-2 infection and that long-COVID rates are varying in the course of the SARS-CoV-2 pandemic.

Source: Nunhofer, et al. Long-COVID Rates Vary Throughout the SARS-CoV-2 Pandemic. Journal of Infectious Diseases & Therapy. Volume 11 • Issue 01 • 1000520. ISSN: 2332-0877.  https://www.researchgate.net/profile/Sandra-Laner-Plamberger/publication/368293143_Long-COVID_Rates_Vary_Throughout_the_SARS-CoV-2_Pandemic/links/63e0dd9062d2a24f920a4d24/Long-COVID-Rates-Vary-Throughout-the-SARS-CoV-2-Pandemic.pdf (Full text)

Severe Fatigue and Persistent Symptoms at Three Months Following SARS-CoV-2 Infections During the Pre-Delta, Delta, and Omicron Time Periods: A Multicenter Prospective Cohort Study

Abstract:

Background: Most research on SARS-CoV-2 variants focuses on initial symptomatology with limited data on longer-term sequelae. We sought to characterize the prevalence and differences in prolonged symptoms at three months post SARS-CoV-2-infection across the three major variant time-periods (pre-Delta, Delta, and Omicron).

Methods: This multicenter prospective cohort study of adults with acute illness tested for SARS-CoV-2 compared fatigue severity, fatigue symptoms, individual and organ system-based symptoms, and presence of ≥3 total symptoms across variants among COVID-positive and COVID-negative participants 3 months after their initial SARS-CoV-2 diagnosis. Variant periods were defined by dates with ≥50% dominant strain. We performed a sensitivity analysis using ≥90% dominance threshold and multivariable logistic regression modeling to estimate the independent effects of each variant adjusting for socio-demographic characteristics, baseline health, and vaccine status.

Results: The study included 3,223 participants (2,402 COVID-positive and 821 COVID-negative). Among the COVID-positive cohort, 463 (19.3%) were pre-Delta, 1,198 (49.9%) during Delta, and 741 (30.8%) during Omicron. Prolonged severe fatigue was highest in the pre-Delta COVID-positive cohort compared with Delta and Omicron cohorts (16.7% vs 11.5% vs 12.3%, respectively; p = 0.017), as was presence of ≥3 prolonged symptoms (28.4% vs 21.7% vs 16.0%; p < 0.001). No difference was seen in the COVID-negative cohort between variant time-periods. In multivariable models, there was no difference in severe fatigue between variants. There was decreased odds of having ≥3 symptoms in Omicron compared with other variants; this was not significant after adjusting for vaccination status.

Conclusions: Prolonged symptoms following SARS-CoV-2 infection were more common among participants infected during the pre-Delta period compared with Delta and Omicron periods; however, these differences were no longer significant after adjusting for vaccination status. This suggests a potential beneficial effect of vaccination on the risk of developing long-term symptoms.

Source: Gottlieb M, Wang R, Yu H, Spatz ES, Montoy JC, Rodriguez R, Chang AM, Elmore JG, Hannikainen PA, Hill M, Huebinger RM, Idris AH, Lin Z, Koo K, McDonald S, O’Laughlin KN, Plumb ID, Santangelo M, Saydah S, Willis M, Wisk LE, Venkatesh A, Stephens KA, Weinstein RA; INSPIRE Group. Severe Fatigue and Persistent Symptoms at Three Months Following SARS-CoV-2 Infections During the Pre-Delta, Delta, and Omicron Time Periods: A Multicenter Prospective Cohort Study. Clin Infect Dis. 2023 Jan 27:ciad045. doi: 10.1093/cid/ciad045. Epub ahead of print. PMID: 36705268.  https://pubmed.ncbi.nlm.nih.gov/36705268/ (Full study available as PDF file)

Factors Associated with Long Covid Symptoms in an Online Cohort Study

Abstract:

Importance Prolonged symptoms following SARS-CoV-2 infection, or Long COVID, is common, but few prospective studies of Long COVID risk factors have been conducted.

Objective To determine whether sociodemographic factors, lifestyle, or medical history preceding COVID-19 or characteristics of acute SARS-CoV-2 infection are associated with Long COVID.

Design Cohort study with longitudinal assessment of symptoms before, during, and after SARS-CoV-2 infection, and cross-sectional assessment of Long COVID symptoms using data from the COVID-19 Citizen Science (CCS) study.

Setting CCS is an online cohort study that began enrolling March 26, 2020. We included data collected between March 26, 2020, and May 18, 2022.

Participants Adult CCS participants who reported a positive SARS-CoV-2 test result (PCR, Antigen, or Antibody) more than 30 days prior to May 4, 2022, were surveyed.

Exposures Age, sex, race/ethnicity, education, employment, socioeconomic status/financial insecurity, self-reported medical history, vaccination status, time of infection (variant wave), number of acute symptoms, pre-COVID depression, anxiety, alcohol and drug use, sleep, exercise.

Main Outcome Presence of at least 1 Long COVID symptom greater than 1 month after acute infection. Sensitivity analyses were performed considering only symptoms beyond 3 months and only severe symptoms.

Results 13,305 participants reported a SARS-CoV-2 positive test more than 30 days prior, 1480 (11.1% of eligible) responded to a survey about Long COVID symptoms, and 476 (32.2% of respondents) reported Long COVID symptoms (median 360 days after infection).

Respondents’ mean age was 53 and 1017 (69%) were female. Common Long COVID symptoms included fatigue, reported by 230/476 (48.3%), shortness of breath (109, 22.9%), confusion/brain fog (108, 22.7%), headache (103, 21.6%), and altered taste or smell (98, 20.6%). In multivariable models, number of acute COVID-19 symptoms (OR 1.30 per symptom, 95%CI 1.20-1.40), lower socioeconomic status/financial insecurity (OR 1.62, 95%CI 1.02-2.63), pre-infection depression (OR 1.08, 95%CI 1.01-1.16), and earlier variants (OR 0.37 for Omicron compared to ancestral strain, 95%CI 0.15-0.90) were associated with Long COVID symptoms.

Conclusions and Relevance Variant wave, severity of acute infection, lower socioeconomic status and pre-existing depression are associated with Long COVID symptoms.

Question What are the patterns of symptoms and risk factors for Long COVID among SARS-CoV-2 infected individuals?

Findings Persistent symptoms were highly prevalent, especially fatigue, shortness of breath, headache, brain fog/confusion, and altered taste/smell, which persisted beyond 1 year among 56% of participants with symptoms; a minority of participants reported severe Long COVID symptoms. Number of acute symptoms during acute SARS-CoV-2 infection, financial insecurity, pre-existing depression, and infection with earlier variants are associated with prevalent Long COVID symptoms independent of vaccination, medical history, and other factors.

Meaning Severity of acute infection, SARS-CoV-2 variant, and financial insecurity and depression are associated with Long COVID symptoms.

Source: Matthew S. Durstenfeld, Michael J. Peluso, Noah D. Peyser, Feng Lin, Sara J. Knight, Audrey Djibo, Rasha Khatib, Heather Kitzman, Emily O’Brien, Natasha Williams, Carmen Isasi, John Kornak, Thomas W. Carton, Jeffrey E. Olgin, Mark J. Pletcher, Gregory M. Marcus, Alexis L. Beatty. Factors Associated with Long Covid Symptoms in an Online Cohort Study. medRxiv 2022.12.01.22282987; doi: https://doi.org/10.1101/2022.12.01.22282987 (Full text)

The effectiveness of coronavirus disease 2019 (COVID-19) vaccine in the prevention of post-COVID-19 conditions: A systematic literature review and meta-analysis

Abstract:

Background: Although multiple studies have revealed that coronavirus disease 2019 (COVID-19) vaccines can reduce COVID-19-related outcomes, little is known about their impact on post-COVID-19 conditions. We performed a systematic literature review and meta-analysis on the effectiveness of COVID-19 vaccination against post-COVID-19 conditions (ie, long COVID).

Methods: We searched PubMed, CINAHL, EMBASE, Cochrane Central Register of Controlled Trials, Scopus, and Web of Science from December 1, 2019, to April 27, 2022, for studies evaluating COVID-19 vaccine effectiveness against post-COVID-19 conditions among individuals who received at least 1 dose of Pfizer/BioNTech, Moderna, AstraZeneca, or Janssen vaccine. A post-COVID-19 condition was defined as any symptom that was present 3 or more weeks after having COVID-19. Editorials, commentaries, reviews, study protocols, and studies in the pediatric population were excluded. We calculated the pooled diagnostic odds ratios (DORs) for post-COVID-19 conditions between vaccinated and unvaccinated individuals. Vaccine effectiveness was estimated as 100% × (1 – DOR).

Results: In total, 10 studies with 1,600,830 individuals evaluated the effect of vaccination on post-COVID-19 conditions, of which 6 studies were included in the meta-analysis. The pooled DOR for post-COVID-19 conditions among individuals vaccinated with at least 1 dose was 0.708 (95% confidence interval (CI), 0.692-0.725) with an estimated vaccine effectiveness of 29.2% (95% CI, 27.5%-30.8%). The vaccine effectiveness was 35.3% (95% CI, 32.3%-38.1%) among those who received the COVID-19 vaccine before having COVID-19, and 27.4% (95% CI, 25.4%-29.3%) among those who received it after having COVID-19.

Conclusions: COVID-19 vaccination both before and after having COVID-19 significantly decreased post-COVID-19 conditions for the circulating variants during the study period although vaccine effectiveness was low.

Source: Marra AR, Kobayashi T, Suzuki H, Alsuhaibani M, Hasegawa S, Tholany J, Perencevich E, Maezato AM, Ricardo VCV, Salinas JL, Edmond MB, Rizzo LV. The effectiveness of coronavirus disease 2019 (COVID-19) vaccine in the prevention of post-COVID-19 conditions: A systematic literature review and meta-analysis. Antimicrob Steward Healthc Epidemiol. 2022 Dec 6;2(1):e192. doi: 10.1017/ash.2022.336. PMID: 36505947; PMCID: PMC9726631. https://www.ncbi.nlm.nih.gov/pmc/articles/PMC9726631/ (Full text)

Infection with SARS-CoV-2 Variants Is Associated with Different Long COVID Phenotypes

Abstract:

COVID-19 has been associated with a broad range of long-term sequelae, commonly referred to as “long-COVID” or “post-COVID-19” syndrome. Despite an increasing body of literature, long COVID remains poorly characterized. We retrospectively analysed data from electronic medical records of patients admitted to the post-COVID-19 outpatient service of the Infectious and Tropical Diseases Unit, Careggi University Hospital, Florence, Italy, between June 2020 and June 2021, 4-12 weeks after hospital discharge.

A total of 428 patients, 41% women, median age 64 years, underwent a follow-up visit a median 53 days after hospital discharge. Overall, 76% patients reported at least one persistent symptom, including dyspnoea (37%), chronic fatigue (36%), insomnia (16%), visual disorders (13%) and brain fog (13%). Increasing oxygen support (OR 1.4, 95% CI 1.1-1.8), use of immunosuppressants (OR 6.4, 95% CI 1.5-28) and female sex (OR 1.8, 95% CI 1.1-2.9) were associated with a higher risk of long COVID symptoms.

Comparison between symptomatic patients infected in the period March-December 2020 (prevalent circulation of wild-type SARS-CoV-2) with those infected in the period January-April 2021 (prevalent circulation of B.1.1.7 Alpha variant) showed a significant modification in the pattern of symptoms belonging to the neurological and cognitive/emotional categories.

Our findings confirmed shortness of breath and chronic fatigue as the most frequent long COVID manifestations, while female sex and severe COVID-19 course were the main risk factors for developing lingering symptoms. SARS-CoV-2 variants may induce different long COVID phenotypes, possibly due to changes in cell tropism and differences in viral-host interaction.

Source: Spinicci M, Graziani L, Tilli M, Nkurunziza J, Vellere I, Borchi B, Mencarini J, Campolmi I, Gori L, Giovannoni L, Amato C, Livi L, Rasero L, Fattirolli F, Marcucci R, Giusti B, Olivotto I, Tomassetti S, Lavorini F, Maggi L, Annunziato F, Marchionni N, Zammarchi L, Bartoloni A. Infection with SARS-CoV-2 Variants Is Associated with Different Long COVID Phenotypes. Viruses. 2022 Oct 27;14(11):2367. doi: 10.3390/v14112367. PMID: 36366465; PMCID: PMC9698829. https://www.ncbi.nlm.nih.gov/pmc/articles/PMC9698829/ (Full text)

Risk of long COVID associated with delta versus omicron variants of SARS-CoV-2

The omicron variant of SARS-CoV-2 (PANGO B.1.1.529) spread rapidly across the world, out-competing former variants soon after it was first detected in November, 2021. According to the Our World in Data COVID-19 database, In Europe, the number of confirmed cases reported between December, 2021, and March, 2022 (omicron period) has exceeded all previously reported cases. Omicron appears to cause less severe acute illness than previous variants, at least in vaccinated populations. However, the potential for large numbers of people to experience long-term symptoms is a major concern, and health and workforce planners need information urgently to appropriately scale resource allocation.
In this case-control observational study, we set out to identify the relative odds of long-COVID (defined following the National Institute for Health and Care Excellence guidelines as having new or ongoing symptoms 4 weeks or more after the start of acute COVID-19) in the UK during the omicron period compared with the delta period. We used self-reported data from the COVID Symptom Study app. (King’s College London Research Ethics Management Application System number 18210, reference LRS-19/20-18210). Data were extracted and pre-processed using ExeTera13 (version 0.5.5).
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Source: Antonelli M, Pujol JC, Spector TD, Ourselin S, Steves CJ. Risk of long COVID associated with delta versus omicron variants of SARS-CoV-2. Lancet. 2022 Jun 18;399(10343):2263-2264. doi: 10.1016/S0140-6736(22)00941-2. PMID: 35717982; PMCID: PMC9212672. https://www.thelancet.com/journals/lancet/article/PIIS0140-6736(22)00941-2/fulltext (Full text)