Study findings updated . AI-assisted evidence summary, not individual medical advice or a clinician endorsement.
Key findings
61% vs 27%Abnormalities in two or more organs on MRI: hospital survivors vs community controls
Hospital COVID survivors had more multi-organ MRI abnormalities than controls.
About 5 months after leaving hospital, 61% of COVID-19 patients had MRI abnormalities in more than one organ, vs 27% of community controls with no evidence of previous COVID-19. The excess was in the lungs, brain and kidneys (renal). Heart (cardiac) and liver scans looked similar in both groups.
COVID serious enough to need a hospital stay can leave marks across several organs months later, not just in the lungs. That argues for follow-up care that looks beyond the chest. Observational study; patients were older and had more obesity and more other illnesses than the 52 controls, so it cannot prove COVID caused the differences.
A UK study that scanned the lungs, heart, brain, liver and kidneys of 259 adults hospitalised with COVID-19 in 2020–2021, plus 52 community controls.
From the study: “Multiorgan abnormalities on MRI were more frequent in patients than in controls (157 [61%] of 259 vs 14 [27%] of 52; p<0·0001)”
61% vs 27%
C-MORE/PHOSP-COVID Collaborative Group. Multiorgan MRI findings after hospitalisation with COVID-19 in the UK (C-MORE): a prospective, multicentre, observational cohort study. The Lancet. Respiratory medicine. 2023.
From the study: “patients had an excess burden of lung, brain, and renal abnormalities; (3) both cardiac and liver MRI abnormalities were similar between patients and our non-COVID-19 control population”
61% vs 27%
C-MORE/PHOSP-COVID Collaborative Group. Multiorgan MRI findings after hospitalisation with COVID-19 in the UK (C-MORE): a prospective, multicentre, observational cohort study. The Lancet. Respiratory medicine. 2023.
From the study: “At a median time of 5 months after hospital discharge, more patients had lung MRI abnormalities”
61% vs 27%
C-MORE/PHOSP-COVID Collaborative Group. Multiorgan MRI findings after hospitalisation with COVID-19 in the UK (C-MORE): a prospective, multicentre, observational cohort study. The Lancet. Respiratory medicine. 2023.
1 in 3 at one year32.6% still had CT lung changes at 1 year, down from 52.9% at mid-term follow-up
1 in 3 still had abnormal lung CT a year after COVID.
Across studies of patients hospitalized with COVID-19, 32.6% still had abnormal lung CT scans at 1 year, down from 52.9% at mid-term checks. Severe or critical cases kept more changes than mild or moderate ones (37.7% vs 20.7%). Scar-like (fibrotic) changes showed little improvement between 4-7 months and 1 year.
Lung changes after a COVID hospital stay often fade with time. But scar-like patches still present after several months tend to stay, especially after severe illness. A pooled analysis of observational studies whose results varied widely, so the exact share is uncertain.
A meta-analysis pooling 15 studies with 3,134 COVID-19 patients who had chest CT scans about one year after illness.
From the study: “While the gradual recovery was seen on CT (52.9% [mid-term] vs. 32.6% [1 year])”
1 in 3 at one year
Watanabe A et al. One-year follow-up CT findings in COVID-19 patients: A systematic review and meta-analysis. Respirology (Carlton, Vic.). 2022.
From the study: “the frequency of CT abnormalities was higher in the severe/critical cases than in the mild/moderate cases (37.7% vs. 20.7%)”
1 in 3 at one year
Watanabe A et al. One-year follow-up CT findings in COVID-19 patients: A systematic review and meta-analysis. Respirology (Carlton, Vic.). 2022.
From the study: “In particular, fibrotic changes showed little improvement between 4-7 months and 1 year after COVID-19.”
1 in 3 at one year
Watanabe A et al. One-year follow-up CT findings in COVID-19 patients: A systematic review and meta-analysis. Respirology (Carlton, Vic.). 2022.
67% lower oddsThree vaccine doses vs unvaccinated: odds of a high CT severity score (odds ratio 0.33)
Two or three vaccine doses were linked to milder COVID lung CT.
Among adults with confirmed COVID-19 who had chest CT in emergency departments, two and three vaccine doses were linked to 53% and 67% lower odds of a high CT severity score (a large share of lung affected) than being unvaccinated. One dose was not. Omicron infections had lower odds of typical COVID pneumonia on CT than Delta (odds ratio 0.46).
Scans from the vaccine and Omicron era look different. Vaccinated people who still needed a scan tended to show less lung involvement, so early-pandemic scan findings may not describe infections today. Retrospective observational study of emergency patients sick enough to need a CT, so it cannot prove vaccines or variants caused the differences.
A review of chest CT reports for 3,876 adults with COVID-19 seen at 93 French emergency departments between July 2021 and March 2022.
From the study: “Two and three vaccine doses were associated with lower odds of typical CT findings (OR, 0.32 and 0.20) and high severity score (OR, 0.47 and 0.33) compared with being unvaccinated”
67% lower odds
Crombé A et al. Impact of Vaccination and the Omicron Variant on COVID-19-related Chest CT Findings: A Multicenter Study. Radiology. 2023.
From the study: “We found that one vaccine dose was not associated with lower odds of typical chest CT findings ( P = .29) or high severity score ( P = .11)”
67% lower odds
Crombé A et al. Impact of Vaccination and the Omicron Variant on COVID-19-related Chest CT Findings: A Multicenter Study. Radiology. 2023.
From the study: “Omicron variant was associated with lower odds of typical CT findings than was Delta variant (odds ratio [OR], 0.46; P < .001)”
67% lower odds
Crombé A et al. Impact of Vaccination and the Omicron Variant on COVID-19-related Chest CT Findings: A Multicenter Study. Radiology. 2023.
Brains 5.5 months olderExtra brain ageing on MRI vs controls scanned twice before the pandemic
Brains aged faster during the pandemic, even without COVID infection.
Healthy adults with one brain MRI before and one after the pandemic began had a 'brain age' (how old the brain looks on MRI) 5.5 months further ahead of their real age than similar people scanned twice before it. This held with or without COVID-19 infection and was stronger in men and people from deprived backgrounds. Only in infected people did it go with worse thinking-test scores.
The stress and disruption of the pandemic years may have left a mark on brain health even in people never infected, with disadvantaged groups affected most. Observational study of healthy middle-aged and older UK Biobank volunteers, so it cannot prove the pandemic itself caused the change.
A UK Biobank study of brain MRIs in 996 healthy adults: 432 scanned before and after the pandemic began and 564 scanned twice before it.
From the study: “The Pandemic group shows on average 5.5-month higher deviation of brain age gap at the second time point compared with controls.”
Brains 5.5 months older
Mohammadi-Nejad AR et al. Accelerated brain ageing during the COVID-19 pandemic. Nature communications. 2025.
From the study: “Accelerated brain ageing is more pronounced in males and those from deprived socio-demographic backgrounds and these deviations exist regardless of SARS-CoV-2 infection.”
Brains 5.5 months older
Mohammadi-Nejad AR et al. Accelerated brain ageing during the COVID-19 pandemic. Nature communications. 2025.
From the study: “However, accelerated brain ageing correlates with reduced cognitive performance only in COVID-infected participants.”
Brains 5.5 months older
Mohammadi-Nejad AR et al. Accelerated brain ageing during the COVID-19 pandemic. Nature communications. 2025.
Screening fell to 1.1%April 2020 screening mammograms as a share of April 2019 volume
Screening mammograms nearly stopped in April 2020, leaving a big deficit.
Screening mammograms in April 2020 fell to 1.1% of April 2019 volume. Volume rebounded strongly by July 2020, but the rebound lagged among Asian and Hispanic women. Total screening for the year through July 2020 was 66.2% of the same period in 2019.
Screening finds breast cancer early. Months of near-zero screening, felt unevenly across groups, could mean some cancers are found later. It counts mammograms at facilities in one US research network through July 2020 and does not track individual women's cancers.
An analysis of 461,083 screening mammograms at 62 US radiology facilities in the Breast Cancer Surveillance Consortium, January 2019 to July 2020.
From the study: “Screening and diagnostic mammography volumes in April 2020 were 1.1% (95% confidence interval [CI] = 0.5% to 2.4%) and 21.4% (95% CI = 18.7% to 24.4%) of the April 2019 prepandemic volumes”
Screening fell to 1.1%
Sprague BL et al. Changes in Mammography Use by Women's Characteristics During the First 5 Months of the COVID-19 Pandemic. Journal of the National Cancer Institute. 2021.
From the study: “Despite a strong overall rebound in mammography volume by July 2020, the rebound lagged among Asian and Hispanic women”
Screening fell to 1.1%
Sprague BL et al. Changes in Mammography Use by Women's Characteristics During the First 5 Months of the COVID-19 Pandemic. Journal of the National Cancer Institute. 2021.
From the study: “The year-to-date cumulative volume of screening and diagnostic mammograms performed through July 2020 was 66.2%”
Screening fell to 1.1%
Sprague BL et al. Changes in Mammography Use by Women's Characteristics During the First 5 Months of the COVID-19 Pandemic. Journal of the National Cancer Institute. 2021.
No sign of heart harmHeart MRI and blood tests 6 months after mild COVID matched antibody-negative peers
Heart scans after mild COVID matched those of antibody-negative colleagues.
At 6 months after mild COVID-19, 74 healthcare workers with antibodies to the virus had no more heart and blood-vessel (cardiovascular) abnormalities on detailed heart MRI and blood tests than 75 matched colleagues without antibodies. Myocarditis-like scarring (scars from heart-muscle inflammation) appeared in 4% of each group.
It suggests mild infection did not quietly damage the hearts of healthy working-age adults, easing a widespread worry. A small study of 149 healthy healthcare workers infected in early 2020; it does not cover severe hospital-level illness or people with many health conditions.
A case-control study of 149 healthcare workers from a 3-hospital cohort, given detailed heart MRI about 6 months after first-wave infection in 2020.
From the study: “At 6 months post-infection, 74 seropositive and 75 age-, sex-, and ethnicity-matched seronegative control subjects were recruited for cardiovascular phenotyping”
No sign of heart harm
Joy G et al. Prospective Case-Control Study of Cardiovascular Abnormalities 6 Months Following Mild COVID-19 in Healthcare Workers. JACC. Cardiovascular imaging. 2021.
From the study: “Cardiovascular abnormalities are no more common in seropositive versus seronegative otherwise healthy, workforce representative individuals”
No sign of heart harm
Joy G et al. Prospective Case-Control Study of Cardiovascular Abnormalities 6 Months Following Mild COVID-19 in Healthcare Workers. JACC. Cardiovascular imaging. 2021.
From the study: “Prevalence of myocarditis-like scar was 4% both in the seropositive and seronegative groups (i.e., no significant difference).”
No sign of heart harm
Joy G et al. Prospective Case-Control Study of Cardiovascular Abnormalities 6 Months Following Mild COVID-19 in Healthcare Workers. JACC. Cardiovascular imaging. 2021.
None of 62 clinic-readyOf 2,212 studies, 62 passed quality checks, and no AI model was of clinical use
None of 2020's AI tools for reading COVID scans was clinic-ready.
Researchers reviewed all papers and preprints from 1 January to 3 October 2020 describing machine-learning (AI) models that diagnose or predict COVID-19 from chest X-rays or CT scans. Of 2,212 studies found, 62 passed quality screening, and none of the models was of potential clinical use because of flawed methods or biases.
Many tools were rushed out to read COVID scans, but none was trustworthy enough to guide care, a cautionary tale for how medical AI is built and tested. Covers only studies released by October 2020, so it cannot judge AI tools developed and tested later.
A systematic review of 2,212 studies of AI models for COVID chest X-rays and CT from 2020, with 62 judged in depth.
From the study: “Our search identified 2,212 studies, of which 415 were included after initial screening and, after quality screening, 62 studies were included in this systematic review.”
None of 62 clinic-ready
Common pitfalls and recommendations for using machine learning to detect and prognosticate for COVID-19 using chest radiographs and CT scans. Nature Machine Intelligence. 2021.
From the study: “Our review finds that none of the models identified are of potential clinical use due to methodological flaws and/or underlying biases.”
None of 62 clinic-ready
Common pitfalls and recommendations for using machine learning to detect and prognosticate for COVID-19 using chest radiographs and CT scans. Nature Machine Intelligence. 2021.
From the study: “for the period from 1 January 2020 to 3 October 2020, which describe new machine learning models for the diagnosis or prognosis of COVID-19 from CXR or CT images”
None of 62 clinic-ready
Common pitfalls and recommendations for using machine learning to detect and prognosticate for COVID-19 using chest radiographs and CT scans. Nature Machine Intelligence. 2021.
Up to 2 years laterPET showed immune activation in people scanned 27 to 910 days after infection
PET scans showed activated immune cells in many organs long after COVID.
In 24 people scanned 27 to 910 days after COVID-19, a PET tracer that marks activated T cells (a type of immune cell) lit up more than in pre-pandemic scans. This showed in the brain stem, spinal cord, bone marrow, lymph tissue, heart and lung tissue, and gut wall. Gut tissue from all five people with long COVID who gave samples held viral genetic material (RNA).
It offers physical evidence that immune activity can stay switched on in many tissues long after infection, a possible clue to long COVID, though not proof of its cause. A very small study of 24 people compared with scans taken before the pandemic, so the findings are early and cannot prove what causes long COVID.
A research study giving whole-body PET scans to 24 people 27 to 910 days after COVID-19, with gut biopsies in five who had long COVID.
From the study: “We performed whole-body positron emission tomography imaging in a well-characterized cohort of 24 participants at time points ranging from 27 to 910 days after acute SARS-CoV-2 infection”
Up to 2 years later
Peluso MJ et al. Tissue-based T cell activation and viral RNA persist for up to 2 years after SARS-CoV-2 infection. Science translational medicine. 2024.
From the study: “was higher compared with prepandemic controls in many regions, including the brain stem, spinal cord, bone marrow, nasopharyngeal and hilar lymphoid tissue, cardiopulmonary tissues, and gut wall”
Up to 2 years later
Peluso MJ et al. Tissue-based T cell activation and viral RNA persist for up to 2 years after SARS-CoV-2 infection. Science translational medicine. 2024.
From the study: “We identified intracellular SARS-CoV-2 single-stranded spike protein-encoding RNA in rectosigmoid lamina propria tissue in all five participants”
Up to 2 years later
Peluso MJ et al. Tissue-based T cell activation and viral RNA persist for up to 2 years after SARS-CoV-2 infection. Science translational medicine. 2024.
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[1]
C-MORE/PHOSP-COVID Collaborative Group. Multiorgan MRI findings after hospitalisation with COVID-19 in the UK (C-MORE): a prospective, multicentre, observational cohort study. The Lancet. Respiratory medicine. 2023.
Sprague BL et al. Changes in Mammography Use by Women's Characteristics During the First 5 Months of the COVID-19 Pandemic. Journal of the National Cancer Institute. 2021.
Joy G et al. Prospective Case-Control Study of Cardiovascular Abnormalities 6 Months Following Mild COVID-19 in Healthcare Workers. JACC. Cardiovascular imaging. 2021.
Common pitfalls and recommendations for using machine learning to detect and prognosticate for COVID-19 using chest radiographs and CT scans. Nature Machine Intelligence. 2021.
Peluso MJ et al. Tissue-based T cell activation and viral RNA persist for up to 2 years after SARS-CoV-2 infection. Science translational medicine. 2024.
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