People infected with Omicron ‘less likely to lose sense of smell compared to Delta’

Findings also support previous studies that suggest incubation time and period of infectiousness for Omicron is shorter than previous variants

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People infected with the Omicron coronavirus variant are less likely to lose their sense of smell compared to Delta, a new study has shown.

Symptoms of Omicron, which is dominant in the UK, do not last as long in those who have been vaccinated than people with Delta, the research said.

Infections from Omicron are at record-level highs in Britain. According to the React-1 Study, 6.37 per cent of the UK population was infected between 8 and 31 March – the highest figure since it began in May 2020.

Researchers from King’s College London also found that some of the more debilitating symptoms typically associated with Covid, such as brain fog, eye burning, dizziness, fever and headaches, were significantly less prevalent in Omicron cases.

The findings support previous studies that suggest the incubation time and period of infectiousness for Omicron is shorter than for previous variants.

According to the study, to be presented at the European Congress of Clinical Microbiology & Infectious Diseases later this month, the biggest difference was in the loss of sense of smell, which appeared in 52.7 per cent of Delta cases, but less than 20 per cent of Omicron cases.

The two Covid symptoms that were consistently more prevalent in both variants - regardless of vaccination status - were a sore throat and hoarse voice.

Dr Cristina Menni, from King’s College London, said: “We observe a different clinical presentation of symptoms in those infected with Omicron compared to Delta.

“As we are moving even further away from the average patient having UK government ‘core’ symptoms i.e fever, persistent cough, loss of smell, our results point to a different selection of symptoms that may indicate infection.

“To protect others, it is still important to self-isolate for five days as soon as you see any symptoms.”

Researchers from King’s College London studied the symptoms of 62,002 vaccinated participants from the Zoe Covid Study App who tested positive between 1 June 2021 and 27 November 2021, when Delta was dominant, and 22 December 2022 to 17 January, when Omicron was dominant.

Professor Ana Valdes, an honorary professor at King’s College London, said: “Although there is still a wide range of duration and severity of symptoms with Omicron, for vaccinated individuals we find on average a shorter duration of symptoms.

“This suggests that the incubation time and period of infectiousness for Omicron may also be shorter.”