Symptoms of the Omicron variant are generally milder than those of Delta and last an average of only 4.4 days in those who have received three doses of the vaccine, less than a cold.
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Symptoms of the Omicron variant (B.1.1.529) of the SARS-CoV-2 coronavirus are generally milder than those caused by the Delta variant, mainly affecting the upper respiratory tract such as the throat, also in people who have received the third dose (the booster or booster) their duration is about half that of a cold. According to a new study, these symptoms, such as sore throat, rhinorrhea (runny nose) and stuffy nose, last an average of 4.4 days, compared to 7 to 10 days for a typical cold. With just two doses of any Covid vaccine, on the other hand, their average duration is 8.3 days. Simply put, the third dose halves the duration of the symptomatic phase of an Omicron infection.
The new investigation was led by an international research team led by scientists from King’s College London, who worked closely with colleagues from the University of Nottingham Center for Biomedical Research, ZOE, the School of Medicine “Pritzker” of the University of Chicago and other institutes. The scientists, coordinated by Dr Cristina Menni, a researcher in the Department of Twins Research and Genetic Epidemiology at the University of London, reached their conclusions after statistically analyzing data reported in the ZOE COVID app by the infected patients. More than 60,000 participants aged 16 to 99 and with a body mass index between 15 and 55 kg/m 2 took part in the study; they had all received at least two doses of any Covid vaccine and had symptomatic infection.
To highlight the differences between the Delta variant and the Omicron variant, Dr. Menni and colleagues matched participants on gender, age, and other characteristics from two different time periods: June 1 to November 27, 2021, during which Delta was prevalent (+70 percent of infections) and from Dec. 20, 2021 to Jan. 17, 2022, when Omicron was prevalent. Comparing data on self-reported symptoms, loss of smell (anosmia) was found to be significantly less common in Omicron patients, with a prevalence of 16.7%, compared to 52.7% during the Delta wave. . Sore throats were more common during the Omicron wave, with a prevalence of 70.5% (compared to 60.8% during the Delta period). The hospitalization rate was also lower in the last wave, at 1.9% versus 2.6% (about 25% less likely). Debilitating symptoms such as brain fog, burning eyes, dizziness, fever and headaches were all significantly less common in Omicron patients, who more often had hoarse voices.
“We are seeing a different clinical presentation of symptoms in patients infected with Omicron compared to Delta. While we move away from the average patient who has the UK Government’s ‘core’ symptoms, eg fever, persistent cough, loss of smell, our results indicate 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 symptoms are noticed,” Dr Menni said in a statement. The UK recently updated the official list of Covid symptoms.
Regarding the duration of symptoms, the study found that patients vaccinated with two doses and infected with Omicron experience them on average two days less than Delta (6.87 days compared to 8.89 days). For those who have the booster, on the other hand, the average duration of the symptomatic phase drops to 4.4 days. “While there is still a wide range of duration and severity of symptoms with Omicron, for those vaccinated, on average we see a shorter duration of symptoms. This suggests that the incubation time and period of infectivity for Omicron may also be shorter,” commented Professor Ana Valdes from King’s College London. Research details “Symptom prevalence, duration, and risk of hospitalization in people infected with SARS-CoV-2 during periods of omicron and delta variant dominance: a prospective observational study from the ZOE COVID study” have been published in the authoritative journal The Lancet.