Booster dose cuts Omicron infection three days earlier than Delta: Lancet

People who have taken a booster dose are likely to recover from Omicron three days earlier than in the case of a Delta infection, claims a study published in The Lancet journal.

The study led by a team at King’s College London showed that the duration of symptoms were significantly shorter for people infected with Omicron compared to the Delta variant, (6.87 days versus 8.89 days) and participants were less likely to be hospitalised.

Researchers noted that symptoms associated with an Omicron infection have less involvement of the lungs and do not last as long in vaccinated people, and more so in people with three doses.

Omicron showed a predominance of viral replication in the upper respiratory tract or in the nose unlike Delta, which majorly affected the lower respiratory tract or in the lungs leading to severe illness, hospitalisation as well as death.

“A third dose of vaccine was associated with a greater reduction in symptom duration in participants infected during Omicron prevalence compared with those infected during Delta prevalence,” said Dr Cristina Menni, from Department of Twin Research and Genetic Epidemiology at King’s, wrote in the paper.

To understand, the team studied the symptoms of 62,002 vaccinated participants in the UK using the ZOE COVID Study App, who tested positive between June 1, 2021 and November 27, 2021, when Delta was dominant, and from December 22, 2021 to January 17, 2022 when Omicron was dominant.

There was also a lower rate of hospital admission during Omicron than during Delta (1.9 per cent vs 2.6 per cent). It was apparently due to the less involvement of the lower respiratory tract, the researchers said.

This is in line with different studies that showed the Omicron variant of Covid to be mild compared to all previous strains, requiring less need for hospitalisation.

The most striking difference between variants was the difference in loss of sense of smell, a common symptom of earlier variants- appearing in 52.7 per cent of Delta cases, only appearing in under 20 per cent of Omicron cases and often days later.

The two symptoms that were consistently more prevalent among Omicron than Delta cases (regardless of vaccination status) were a sore throat and a hoarse voice.

Moreover, many debilitating symptoms, such as brain fog, eye burning, dizziness, fever, and headaches, though still occurring, were all significantly less prevalent in Omicron cases.

“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 acore’ symptoms that is, 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,” Menni said.




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