The most up to date Omicron symptoms list reports the most common side effects as those that overlap with a cold or the flu.
Professor Tim Spector, who helped found the Covid Zoe app, shared he had contracted Omicron last week.
In a YouTube video he filmed while isolating on Thursday, the professor said he had a "loss of energy" and was "bunged up".
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He continued: "I have every sympathy for those of you that have been reporting it to us.
"It does start exactly like a cold, can't tell it apart except much more fatigue than I've ever had with a cold, and it lays you out for a couple of days."
Omicron symptoms vastly differ than those originally reported with Covid-19, though the government and NHS still uses the classic symptoms - a fever, new and continuous cough, and a loss or change to taste or smell - in its guidance.
Hitting out at this, Prof Spector added: "According to the government, I wouldn't have covid because I didn't have any of the classic symptoms... like half of you.
"Thank God for lateral flow tests, hey?"
Later in the video, he said 50% of cases now are respiratory symptoms alone.
The most commonly-reported symptom in those with Omicron is a runny nose - with some 74% saying they had this side effect of the virus.
Other symptoms to make the top five include a headache, sore throat, fatigue and sneezing.
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