16 out of 18 guests who recently attended a birthday party have all since been diagnosed with the Omicron Covid-19 variant.
A professor who specialises in the virus revealed the real-life example to illustrate the high transmissibility of the new strain.
Every one of the 16 people who were told that they were either positive, or were probably positive, for the variant in the days following the 60th birthday celebration were either double or triple vaccinated.
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The information was revealed by professor of genetic epidemiology at King’s College London Tim Spector, as reported by Hull Live.
Professor Spector previously co-founded the ZOE Covid Study app, which studies the symptoms of COVID-19 and track the spread of the virus.
Speaking on Good Morning Britain, he said: "A regular ZOE user entertained a 60th birthday party gathering with 18 guests.
"All of them had taken lateral flow tests prior to the gathering. On Sunday they were informed that one of the guests - who happened to be a teacher - had tested positive and the following week 16 out of 18 had fallen ill in some way.
"They were subsequently informed by NHS test and trace that it was Omicron or probable Omicron and they were waiting to get the genetic sequencing confirmations.
"Quite a few of them had nausea, slight temperature, sore throats and headaches."
Although nobody was bad enough to need a doctor or go to hospital, all had been "double and triple vaccinated", added Prof Spector.
The fact that none of the cases required medical assistance indicates that the vaccines "clearly" reduced the severity of the illness, he said.
