The latest UK study: Omikeron causes different symptoms than Delta, and the loss of smell or taste is less likely

A new study in the United Kingdom found that the Omiljun strain caused different symptoms than the Delta strain of the new crown variant virus, with less likely loss of smell or taste, and shorter duration of symptoms and faster recovery.

The large study, which targets nearly 10,000 Britons who have been vaccinated against COVID-19, was published on the Lancet website on 7 April and will be presented at the European Congress of Clinical Microbiology and Infectious Diseases this month.

Symptom duration is on average two days shorter

According to the study synopsis on The Lancet's website, the study, led by King's College London, is based on data from 63,002 COVID patients collected by the Zoe Covid research app in the UK.

Of the 63,002 COVID-19 patients, the researchers sampled nearly 10,000 patients and divided them into two groups based on time. One group was confirmed to be infected during the spread of Delta as the dominant strain from June 1 to November 27 last year, and the other was the confirmed infected during the spread of the dominant strain in Aumiqueron from December 20 to January 17 this year. The two groups of COVID-19 patients participating in the study were 4990 people each.

The researchers also took into account the matching degrees of age, sex, and vaccinations when grouping. The participants were between the ages of 16 and 99, both living in the UK, had a BMI of 15 to 55, had at least two doses of the COVID-19 vaccine, were symptomatic, and tested positive for COVID-19.

After comparing the clinical symptoms of the two groups of COVID-19 patients, the researchers found that patients in the "Delta period" and "Omikron period" were different in terms of symptom manifestations, duration of symptoms, or probability of hospital admission.

From the perspective of symptom manifestations, whether or not there is loss of smell is the biggest difference between the two groups of patients. "Delta period", 52.7% of patients developed symptoms of loss of smell, but only 17% of the "Omikeron period". Sore throat and hoarseness, although present in both periods, are more common in patients of the "Omikejong period".

The researchers also found that in patients during the "Omikeron period," debilitating symptoms such as brain fog, eye aches, dizziness, fever, and headache were significantly less than those in the "Delta period."

Among the three typical COVID-19 symptoms of fever, loss of smell, and persistent cough, patients with the "Omikeron period" are about 50% more likely to develop at least one symptom than those in the "Delta period".

In terms of the duration of symptoms, patients in the two periods also differed.

Compared with the "Delta period", the "Omi kerong period" patients have a shorter duration of symptoms, especially in the group that has been vaccinated with booster needles.

Overall, among the vaccinated population, the duration of symptoms in patients in the "Delta period" averaged about 8.9 days, compared with about 6.9 days in the "Omikeron period", a difference of 2 days.

Specifically, in the group that received only two doses of the vaccine and did not receive a booster injection, the average duration of symptoms in patients in the "Delta period" was 9.6 days, compared with 8.3 days in the "Omikeron period", a difference of only 1.3 days.

In the population that had received two doses of the vaccine and one booster, the duration of symptoms in patients in the "Delta period" averaged 7.7 days, compared with 4.4 days in the "Omikeron period", a difference of 3.3 days.

In addition, the study also found that the "Omikeron period" was 25% less likely to be hospitalized for COVID-19 cases than the "Delta period" and 2.5 times more likely to recover within a week.

Self-isolation is still required after infection

The researchers said that the short duration of symptoms in Omiljung (to be confirmed by viral load studies) may mean that the strain has a short incubation period and a shorter infection period, which will affect health policies and public health guidelines in the workplace. At the same time, the latest findings also support the results of earlier studies in South Africa, France, South Korea and other countries, showing that infection with Omiljung is not as severe as the previous mutant strain.

Ana Valdes, a professor emeritus at King's College London, said that while there are still individual differences in the duration and severity of Omiljung's symptoms, for individuals who have been vaccinated, on average, the duration of symptoms is shorter than that of Delta, "which suggests that the incubation and infection periods of Omiqueron may also be shorter".

Dr Cristina Menni of King's College London said the clinical symptoms of Opmi kerong were different compared to Delta. However, "in order to protect others, it is still important to self-isolate for five days, regardless of the symptoms"

Tim Spector, a professor at King's College London, one of the study authors, noted that documenting symptoms is an important research tool, with symptom changes reminding people of what to look out for when the next mutant strain emerges and the need to react faster in the delivery of public health messages.

He believes the UK needs to learn a "lesson" in this regard. At the time of the spread of the Omiljung strain, public health guidelines were not released to the public in a timely manner due to the government's failure to pay attention to the data on symptom changes reported by researchers, indicating that sore throat was replacing loss of smell as the main symptom.

However, the researchers admit that the study also has some limitations. For example, because most of the patients involved in the study were vaccinated, it was not possible to compare differences in symptom manifestations, duration, and risk of admission between the two variants in the unvaccinated population. As another example, whether infected Ormikeron or Delta was assigned based on the prevalence of the British population at the time, rather than from individual sequencing. Patient self-reported data can lead to informational bias.

Dr David Strain, a senior clinical lecturer at the University of Exeter School of Medicine who was not involved in the study, said the latest findings coincided with the situation when the BA.1 subtype of the Aumechjong strain dominated at the beginning of the year, but now that the BA.2 subtype has replaced the former as mainstream, the situation has changed again.

Still, Meney said the latest data from the Zoe app shows no change in symptoms from the BA.1 subtype.

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Source: Author: Liao Qin