There’s still a lot we don’t know about the omicron coronavirus variant, including whether it causes more severe COVID-19 or the degree to which it evades vaccines’ defenses in real-world settings.
But early data collected in London reveals the answer to a question we’re all asking: Does omicron cause different symptoms than delta and other variants?
Not quite, according to the ZOE COVID Study — an app some U.K. residents use to self-report information about their coronavirus vaccination and infections.
A comparison of data from thousands of people who tested positive for COVID-19 in October when the delta variant was dominant in London compared to December when omicron took over reveals “no clear difference in early symptoms (3 days after test).”
The top five reported symptoms in both periods, however, suggest the common cold you think you have may actually be COVID-19.
Runny nose, headache, fatigue, sneezing and sore throat were the most common symptoms among London residents, with some people also reporting loss of appetite and brain fog, data shows.
Typically, COVID-19’s “classic three symptoms” include fever, cough or loss of smell or taste, but only 50% of people in the early analysis infected with delta or omicron experienced them.
A Centers for Disease Control and Prevention study on 43 COVID-19 patients sick with the omicron variant found cough, fatigue, congestion and runny nose were the most commonly reported symptoms.
But experts warn against depending on symptoms to determine if you’re sick — and with what.
“The trick is you’re not going to be able to tell the difference between omicron, delta, lambda, plain COVID from the beginning,” Dr. Emily Landon, chief hospital epidemiologist at University of Chicago Medicine, told NBC Chicago. “Influenza or even common rhinovirus causes most of our common colds in the winter. You’re not going to know the difference between those if you just look at your symptoms.”
“For many people, those symptoms are overlapping,” Landon told the outlet. “You’re just not going to know especially at the beginning of an illness, what kind of illness you have. You have to get tested.”
The omicron variant has been detected in at least 39 states and more than 75 countries, CDC Director Dr. Rochelle Walensky said during a Dec. 17 White House COVID-19 briefing.
Does the omicron variant cause more severe disease?
Doctors caring for COVID-19 patients in South Africa — where the variant was first detected — said in November the omicron cases they treated at the time were mild, and mostly among younger people.
Dr. Angelique Coetzee, chair of the South African Medical Association, told BBC her omicron patients had scratchy not sore throats, and didn’t have a cough or loss of smell or taste.
More recent data from the country shows the risk of hospital admission among adults infected with omicron is 29% lower than that of adults infected with the original coronavirus strain when the pandemic began in 2020.
However, a study by the Imperial College London found no evidence that omicron causes less severe illness than delta, based on the proportion of infected people who report symptoms or seek hospital care.
It remains unclear if omicron itself is less severe or if other factors, such as characteristics of the infected population, may play a role, experts say. Meanwhile, early studies show two doses of a COVID-19 vaccine may not protect you against omicron infection, but can against hospitalization and death; booster shots significantly increase immunity.
Dr. Anthony Fauci, chief White House medical adviser, said the “seriousness of infection” with omicron is “still up in the air right now.”
“Certainly, looking at what we see, it does not look like it is more severe, but we have to withhold judgment,” Fauci said during the Dec. 17 White House briefing.
It’s clear omicron is more contagious than other variants, he added, especially if you look at New York, where omicron infections broke the state’s record for daily new reported cases for two consecutive days.
Dr. Francis Collins, director of the National Institutes of Health, told NPR the U.S. could see 1 million new COVID-19 infections per day if we let our guards down.
Experts say the best way to protect yourself against omicron is to get tested frequently, social distance, get vaccinated and boosted, and wear a face mask indoors.