Researchers at King's College London and ZOE scientists studied the symptoms of 62,002 vaccinated participants from the United Kingdom, thanks to the application of the ZOE COVID study. According to data published in the journal in The Lancet, the symptoms of Ómicron can disappear in half the time of the common cold when the patient received a booster vaccine against COVID-19.
In addition, they found that the duration of symptoms was also significantly shorter for Ómicron compared to the Delta variant (6.87 days versus 8.89 days) and that participants were less likely to be hospitalized. To learn this data, scientists divided volunteers into two groups: those who tested positive between June 1, 2021 and November 27, 2021, when Delta was dominant, and those who were infected from December 22, 2021 to January 17, 2022 when Ómicron was dominant.
Booster dose: milder symptoms and shorter duration of illness
Scientists at King's College London even found notable differences in recovery times according to the number of doses the volunteers had received. They noted that those who received the triple dose reported symptoms that lasted an average of 4.4 days, compared to 8.3 days for those who received two vaccines.
This represents about half the time of the symptoms of the common cold, which persists from seven to ten days. For those with a booster, the infection with Omicron was 3.3 days shorter than a Delta infection, which lasts 7.7 days with a third dose or 9.6 days for those who received double immunization. In addition, the findings indicated that the virus was evolving to be less virulent over time and also that receiving a booster dramatically reduced the symptomatic period.
The most striking difference between the variants was the loss of the sense of smell, a common symptom of the previous variants, which appears in 52.7% of those infected with Delta, whereas it only appears in less than 20% of cases of Ómicron and days later. The two symptoms that were consistently most frequent among both variants (regardless of vaccination status) were sore throat and hoarse voice. In addition, many debilitating symptoms, such as mental confusion, burning eyes, dizziness, fever and headaches, although they still occur, were significantly less frequent in cases of Omicron.
The researchers noted in their paper that “the symptoms associated with an Omicron infection involve the lungs less and do not last as long in vaccinated people.” “We observed 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 who has the central symptoms reported by the UK government, i.e. fever, persistent cough, loss of smell, our results point to a different selection that may indicate infection. To protect others, it is still important to self-isolate for five days as soon as you see any symptoms,” Cristina Menni, a member of the team in charge of the investigation, told specialist.
Since its appearance in December 2021, Ómicron has spread to more than 80 countries and has become the dominant COVID-19 variant in the UK, surpassing the Delta. Early reports, for example, of a recent study from South Africa indicated that the Omicron variant was significantly less severe than previous dominant variants, with lower rates of hospitalization. However, the King's Colles study is the largest population-based and the most detailed so far.
Tim Spector, lead scientist in the ZOE COVID study and professor at King's College London, noted: “It is an amazing scientific feat that just a few months after Ómicron settled in the UK, the teams at King's College London and ZOE were able to produce quick and conclusive answers to these clinical questions clues about symptoms and severity”. “This research shows that reinforcements are worthwhile,” Menni concludes. Even if you aren't likely to have a serious infection, it's not pleasant to get COVID. But if you have a booster, you reduce the risk of infection by half, which means having shorter and milder symptoms.”
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