Study findings updated . AI-assisted evidence summary, not individual medical advice or a clinician endorsement.
THE SHORT VERSION
What’s worth knowing.
The key findings, what they mean, and the context that matters.
THE HEADLINE TAKEAWAY60.5% lost smellOf US adults diagnosed with COVID-19 by 2021, in a nationally representative survey
Most US adults with COVID-19 in 2021 reported losing smell or taste.
In a 2021 national survey weighted to represent US adults, 14% had been diagnosed with COVID-19. Of those, 60.5% reported losing smell and 58.2% losing taste. Smell came back fully for 72.2% and partly for 24.1%, while 3.7% reported no smell recovery. People with more severe overall COVID-19 symptoms were less likely to recover.
Losing smell or taste was the usual experience for people diagnosed in 2021, not a rare quirk. Most recover, but even a small share of millions of infected adults is a large group still living without full smell. Answers came from a self-reported national survey (2021 National Health Interview Survey), so smell loss and recovery were not confirmed with smell tests.
See the evidence
A US household survey, the 2021 National Health Interview Survey, weighted to represent all US adults and asking about COVID-19 diagnosis, smell and taste loss, and recovery.
From the study: “In 2021, 35.8 million or 14% of the adult population”
60.5% lost smell
Mitchell MB et al. Smell and Taste Loss Associated with COVID-19 Infection. The Laryngoscope. 2023.
From the study: “Following infection, 72.2% (69.9-74.3%), 24.1% (22.2-26.2%), and 3.7% (3.0-4.6%) of the patients experienced complete, partial, and no smell recovery, respectively.”
60.5% lost smell
Mitchell MB et al. Smell and Taste Loss Associated with COVID-19 Infection. The Laryngoscope. 2023.
Loss of smell was far less common during Omicron than Delta.
1 in 6 with OmicronLost smell (16.7%) in the Omicron wave vs 52.7% in Delta; vaccinated UK app users
Among vaccinated UK adults who logged symptoms in the ZOE app, 16.7% of those infected while Omicron dominated lost their sense of smell, versus 52.7% of matched people infected during Delta. The throat took over: sore throat rose to 70.5% from 60.8%, and hoarse voice also became more common.
A sore or hoarse throat, not a vanished sense of smell, became the more typical sign in the Omicron period, so having a normal sense of smell does not mean you don't have COVID-19. Self-reported symptoms from vaccinated UK app users, grouped by which variant dominated when they tested positive rather than by a confirmed variant.
See the evidence
A UK app-based study: 4,990 vaccinated people infected during Omicron dominance were matched by age, sex and vaccine doses to 4,990 infected during Delta, June 2021 to January 2022.
From the study: “Loss of smell was less common in participants infected during omicron prevalence than during delta prevalence (16·7% vs 52·7%, odds ratio [OR] 0·17; 95% CI 0·16-0·19, p<0·001).”
1 in 6 with Omicron
Menni C et al. Symptom prevalence, duration, and risk of hospital admission in individuals infected with SARS-CoV-2 during periods of omicron and delta variant dominance: a prospective observational study from the ZOE COVID Study. Lancet (London, England). 2022.
From the study: “Sore throat was more common during omicron prevalence than during delta prevalence (70·5% vs 60·8%, 1·55; 1·43-1·69, p<0·001).”
1 in 6 with Omicron
Menni C et al. Symptom prevalence, duration, and risk of hospital admission in individuals infected with SARS-CoV-2 during periods of omicron and delta variant dominance: a prospective observational study from the ZOE COVID Study. Lancet (London, England). 2022.
From the study: “However, sore throat and hoarse voice were significantly more likely to be present during omicron prevalence than during delta prevalence”
1 in 6 with Omicron
Menni C et al. Symptom prevalence, duration, and risk of hospital admission in individuals infected with SARS-CoV-2 during periods of omicron and delta variant dominance: a prospective observational study from the ZOE COVID Study. Lancet (London, England). 2022.
Two years after mild COVID-19, smell loss still outpaced matched controls.
17-point gap at 2 yearsMeasured smell loss in 27.9% after mild COVID-19 vs 10.8% in matched controls
Adults who had mild COVID-19 took lab smell tests 2 years later and were compared with matched people without COVID-19. Smell problems showed up in 27.9% versus 10.8%, a 17.2-point excess. Rates were falling, down from 42.0% a year earlier, but 3.2% still had no sense of smell at all. Taste problems were not clearly more common than in controls.
Most people's smell keeps improving, but a real share of people who had only mild COVID-19 still had measurably weaker smell two years on, beyond what is normal in similar people who never had it. A small case-control study (93 people with past mild COVID-19, 93 matched controls), so the true size of the gap is uncertain.
See the evidence
A prospective case-control study of 93 adults with PCR-confirmed mild COVID-19 and 93 matched controls, all given detailed smell and taste tests about 1 and 2 years after infection.
From the study: “Subjects with prior COVID-19 were more likely than controls to have an olfactory dysfunction (27.9% vs. 10.8 %; absolute difference, 17.2%; 95% CI, 5.2% to 28.8%)”
17-point gap at 2 years
Boscolo-Rizzo P et al. Psychophysical assessment of olfactory and gustatory function in post-mild COVID-19 patients: A matched case-control study with 2-year follow-up. International forum of allergy & rhinology. 2023.
From the study: “At 2-year follow-up, cases exhibited a decrease in the prevalence of olfactory (27.9% vs. 42.0%; absolute difference, -14.0%; 95% CI, -21.8% to -2.6%; p = 0.016)”
17-point gap at 2 years
Boscolo-Rizzo P et al. Psychophysical assessment of olfactory and gustatory function in post-mild COVID-19 patients: A matched case-control study with 2-year follow-up. International forum of allergy & rhinology. 2023.
From the study: “Overall, 3.2% of cases were still anosmic 2 years after the infection.”
17-point gap at 2 years
Boscolo-Rizzo P et al. Psychophysical assessment of olfactory and gustatory function in post-mild COVID-19 patients: A matched case-control study with 2-year follow-up. International forum of allergy & rhinology. 2023.
Distorted smells often began more than a month after COVID-19 symptoms.
64% had distorted smellOf 231 people with COVID-related smell loss answering surveys at medical practices
Among 231 people with smell loss tied to COVID-19, 148 (64.1%) reported parosmia, meaning smells seemed wrong or distorted, at some point. It began within 1 week of first COVID-19 symptoms for 25.4%, but more than 1 month later for 43.4%. Those with parosmia scored better on a smell test yet reported worse quality of life, and they were younger on average.
Smells turning strange a month or more after COVID-19 were common in this group, so a late change is not unusual. It can weigh on daily life even when a standard smell test looks better. Survey of people already seeking care for smell loss at ENT and primary care practices (August 2020 to March 2021), so it may overstate how often parosmia follows infection overall.
See the evidence
A survey study of 231 adults with smell loss after confirmed or suspected COVID-19, recruited from ear, nose and throat and primary care practices between August 2020 and March 2021.
From the study: “A total of 148 (64.1%) of 231 respondents reported parosmia at some point.”
64% had distorted smell
Lerner DK et al. Clinical Features of Parosmia Associated With COVID-19 Infection. The Laryngoscope. 2022.
From the study: “Parosmia developed within 1 week of any COVID-19 symptom onset in 25.4% of respondents, but more than 1 month after symptom onset in 43.4% of respondents.”
64% had distorted smell
Lerner DK et al. Clinical Features of Parosmia Associated With COVID-19 Infection. The Laryngoscope. 2022.
Smell training worked no better than placebo for COVID-19 smell loss.
123 patients, no benefitSmell training vs placebo for COVID-19 smell loss; 84.5% overall reached normal smell
In a double-blind trial, adults with COVID-19 smell loss did standard smell training (regularly sniffing set odors) or a placebo. Among 123 who finished, training was no better once group differences were accounted for. Overall, 84.5% reached normal smell. In an exploratory look, starting treatment within 30 days was linked to a 58% higher chance of full recovery, in either group.
Smell training is widely recommended, yet here it did not beat a placebo. Most people regained normal smell either way, which is encouraging for anyone early in recovery. One randomized trial in which the training group started with worse smell scores and more steroid use, which may have tilted results, and the early-start finding is exploratory.
See the evidence
A randomized, double-blind, placebo-controlled trial of smell training in people with COVID-19 smell loss, with 123 completing 180 days of follow-up and monthly smell testing.
From the study: “A total of 123 participants completed follow-up: 68 in the OT group and 55 in the PB group.”
123 patients, no benefit
Serrano TLI et al. Olfactory training for the treatment of COVID-19 related smell loss: a randomised double-blind controlled trial. Rhinology. 2025.
Platelet-rich plasma injections improved smell scores in a small trial.
3.7 points better smellBigger gain on a smell test at 3 months with PRP shots than with saline
In a randomized trial, people with lasting smell loss after COVID-19 got three injections high in the nose of either platelet-rich plasma (PRP, a growth-factor concentrate made from their own blood) or saline. At 3 months PRP gave a 3.67-point bigger gain on a smell test, and more people improved meaningfully: 57.1% vs 8.3%. Their own ratings of their smell did not differ.
PRP is one of the few treatments for lingering COVID-19 smell loss to beat a placebo in a randomized trial, but the trial was tiny and people did not feel a difference, so larger studies are needed. A small randomized trial in which 35 patients enrolled and only 26 finished, so the size of the benefit is uncertain.
See the evidence
A multi-institution randomized controlled trial in people with tested smell loss 6 to 12 months after COVID-19, comparing nose injections of platelet-rich plasma with saline.
From the study: “PRP treatment resulted in a 3.67-point (95% CI: 0.05-7.29, p = 0.047) greater improvement in olfaction compared with the placebo group at 3 months”
3.7 points better smell
Yan CH et al. Use of platelet-rich plasma for COVID-19-related olfactory loss: a randomized controlled trial. International forum of allergy & rhinology. 2023.
From the study: “a higher response rate (57.1% vs 8.3%, odds ratio 12.5 [95% exact bootstrap confidence interval, 2.2-116.7])”
3.7 points better smell
Yan CH et al. Use of platelet-rich plasma for COVID-19-related olfactory loss: a randomized controlled trial. International forum of allergy & rhinology. 2023.
From the study: “Patients were randomized to three intranasal injections of either PRP or sterile saline into their olfactory clefts.”
3.7 points better smell
Yan CH et al. Use of platelet-rich plasma for COVID-19-related olfactory loss: a randomized controlled trial. International forum of allergy & rhinology. 2023.
Sudden hearing loss did not rise after COVID-19 vaccination in Finland.
5.5 million, no increaseSudden hearing loss after COVID-19 shots or infection, Finnish national registries
Researchers followed 5.5 million Finnish residents through national health records, comparing new diagnoses of sudden sensorineural hearing loss (a sudden drop in inner-ear hearing) after each COVID-19 vaccine dose with rates before the pandemic. They found no increase after any vaccination, and SARS-CoV-2 infection showed no increase in cases either.
Reports of sudden hearing loss after COVID-19 shots raised worry. Across a whole country's health records, no increase showed up after vaccination or after infection. Cases were identified from specialist-care diagnosis codes rather than hearing tests, and the authors say results still need checking where hearing loss can be measured.
See the evidence
A nationwide registry cohort of 5.5 million people in Finland, January 2019 to April 2022, comparing sudden hearing loss diagnoses after COVID-19 vaccination or infection with pre-pandemic rates.
From the study: “This register-based country-wide retrospective cohort study of 5.5 million Finnish residents was conducted from January 1, 2019, to April 20, 2022”
5.5 million, no increase
Nieminen TA et al. Sudden Hearing Loss Following Vaccination Against COVID-19. JAMA otolaryngology-- head & neck surgery. 2023.
Nearly all ICU COVID-19 patients assessed had swallowing problems; most recovered.
94% struggled to swallowICU COVID-19 patients referred for swallow assessment, Delta and later waves
Among 235 adults in intensive care for COVID-19 in Delta and later waves who were referred for a swallowing assessment, 94% had dysphagia (trouble swallowing) and 45% had the most severe level, taking nothing by mouth. By hospital discharge, 71% had recovered, after a median of 30 days. Longer time on a breathing machine was linked to slower recovery.
Surviving the ICU is not the end of the story: many patients need weeks before they can eat and drink normally again, and some still struggle to swallow when they go home. Observational study limited to ICU patients referred for swallowing assessment, so it cannot say how common swallowing problems are among all ICU COVID-19 patients.
See the evidence
A prospective study across 26 public hospital ICUs in New South Wales over 12 months, following 235 COVID-19 patients seen for swallowing assessment during Delta and later variants.
From the study: “Prevalence of dysphagia was 94% with the majority (45%) exhibiting profound dysphagia (Functional Oral Intake Scale = 1) at initial assessment.”
94% struggled to swallow
Clayton NA et al. Dysphagia Prevalence and Outcomes Associated with the Evolution of COVID-19 and Its Variants in Critically Ill Patients. Dysphagia. 2024.
From the study: “Dysphagia recovery by hospital discharge was observed in 71% (median duration = 30 days [IQR = 17-56 days]).”
94% struggled to swallow
Clayton NA et al. Dysphagia Prevalence and Outcomes Associated with the Evolution of COVID-19 and Its Variants in Critically Ill Patients. Dysphagia. 2024.
From the study: “235 participants (63% male, median age = 58 years) were recruited.”
94% struggled to swallow
Clayton NA et al. Dysphagia Prevalence and Outcomes Associated with the Evolution of COVID-19 and Its Variants in Critically Ill Patients. Dysphagia. 2024.
Persistent smell or taste problems were linked to fatigue, memory and sleep difficulties
Compared with recovered self-reported smell or taste dysfunction, persistent dysfunction was associated with higher odds of fatigue, memory difficulties and self-reported insomnia.
The fatigue and memory findings concern four years after symptom onset. These self-reported associations do not show that sensory problems caused the other symptoms. A source notice flags conflicting publication-date metadata.
Study details & original results
Hansen, Joachim Skovgaard et al.. Patient burden of chemosensory dysfunction and long COVID.. Danish medical journal. 2026. [Source notice: Online publication: 2026-06-09 (PubMed 42592765 and publisher); Crossref currently records a conflicting 2016 date.]
Association between persistent versus recovered self-reported chemosensory dysfunction and fatigue four years after symptom onset
OR 4.33
Association between persistent versus recovered self-reported chemosensory dysfunction and memory difficulties four years after symptom onset
OR 3.30
Association between persistent chemosensory dysfunction and self-reported insomnia compared with recovered dysfunction
Smell loss and taste problems had separate pooled prevalence estimates
44%
Among confirmed COVID-19 patients in Saudi Arabia, pooled prevalence was 44% for loss of smell and 46% for taste dysfunction.
The review combined differing methods, mostly self-reported measures, and lacked a prospectively registered protocol. These separate outcomes do not give a probability of persistent symptoms for every patient.
Study details & original results
Aldrees, Turki. Assessing the prevalence of anosmia and taste dysfunction in COVID-19 patients in Saudi Arabia: a systematic review and meta-analysis.. Frontiers in public health. 2026.
Pooled prevalence of anosmia among confirmed COVID-19 patients in Saudi Arabia; interpretation is limited by methodological heterogeneity, predominantly self-reported measures, and the absence of a prospectively registered protocol.
44% 95% CI: 37-52%
Pooled prevalence of taste dysfunction among confirmed COVID-19 patients in Saudi Arabia; interpretation is limited by methodological heterogeneity, predominantly self-reported measures, and the absence of a prospectively registered protocol.
Dates show when findings were added here, not when papers were published. Study populations and comparisons differ.
WHEN YOU WANT TO GO DEEPERSee all 6 findingsOriginal results, comparisons and study details.
2 of 2 source groupsFindings stay together with their study.
SOURCE 034 findings
Hansen, Joachim Skovgaard et al.. Patient burden of chemosensory dysfunction and long COVID.. Danish medical journal. 2026. [Source notice: Online publication: 2026-06-09 (PubMed 42592765 and publisher); Crossref currently records a conflicting 2016 date.]
Aldrees, Turki. Assessing the prevalence of anosmia and taste dysfunction in COVID-19 patients in Saudi Arabia: a systematic review and meta-analysis.. Frontiers in public health. 2026.
Pooled prevalence of taste dysfunction among confirmed COVID-19 patients in Saudi Arabia; interpretation is limited by methodological heterogeneity, predominantly self-reported measures, and the absence of a prospectively registered protocol.
Pooled prevalence of anosmia among confirmed COVID-19 patients in Saudi Arabia; interpretation is limited by methodological heterogeneity, predominantly self-reported measures, and the absence of a prospectively registered protocol.
Browse the 11 original sourcesThe complete bibliography behind this monitor.
[1]
Salimi, Sajjad et al.. Effect of glucocorticoids on smell sensation in patients with non-traumatic olfactory disorders: a systematic review and meta-analysis.. European journal of clinical pharmacology. 2026.
Aldrees, Turki. Assessing the prevalence of anosmia and taste dysfunction in COVID-19 patients in Saudi Arabia: a systematic review and meta-analysis.. Frontiers in public health. 2026.
Hansen, Joachim Skovgaard et al.. Patient burden of chemosensory dysfunction and long COVID.. Danish medical journal. 2026. [Source notice: Online publication: 2026-06-09 (PubMed 42592765 and publisher); Crossref currently records a conflicting 2016 date.]
Menni C et al. Symptom prevalence, duration, and risk of hospital admission in individuals infected with SARS-CoV-2 during periods of omicron and delta variant dominance: a prospective observational study from the ZOE COVID Study. Lancet (London, England). 2022.
Boscolo-Rizzo P et al. Psychophysical assessment of olfactory and gustatory function in post-mild COVID-19 patients: A matched case-control study with 2-year follow-up. International forum of allergy & rhinology. 2023.
Yan CH et al. Use of platelet-rich plasma for COVID-19-related olfactory loss: a randomized controlled trial. International forum of allergy & rhinology. 2023.
Clayton NA et al. Dysphagia Prevalence and Outcomes Associated with the Evolution of COVID-19 and Its Variants in Critically Ill Patients. Dysphagia. 2024.
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