COVID Paper Database
Visual Abstract
Outbreak caused by the SARS-CoV-2 Omicron variant in Norway, November to December 2021
Lin T. Brandal, Emily MacDonald, , Lamprini Veneti , Tine Ravlo , Heidi Lange , Umaer Naseer , Siri Feruglio , Karoline Bragstad , Olav Hungnes , Liz E. Ødeskaug , Frode Hagen , Kristian E. Hanch-Hansen , Andreas Lind , Sara Viksmoen Watle , Arne M. Taxt , Mia Johansen , Line Vold , Preben Aavitsland , Karin Nygård , Elisabeth H. Madslie
Summarized by Charles Li, MD
March 9, 2022
Summary
💦
Omicron spreads quickly
This study demonstrated key evidence on just how quickly Omicron can spread.
💉
Omicron can affect the vaccinated.
Despite a 96% vaccination rate, the majority of those exposed to omicron in this outbreak became infected
🤒
Symptoms can vary.
Unlike other variants, loss of taste and/or smell was rare in this case
Visual Abstract
Click to expand
One of the best-documented outbreaks of Omicron happened at a Christmas party in Norway.
In November 2021, 117 individuals gathered at a restaurant for a private event. 96% of those at the party were fully vaccinated against COVID-19. On November 30th, officials detected an outbreak.
Officials isolated and tested everyone at the party for COVID-19.
Eventually, 74% of those tested developed the Omicron variant of COVID-19.
We observed an attack rate of 74% and most cases developed symptoms. As at 13 December, none have been hospitalised. Most participants were 30–50 years old. Ninety-six percent of them were fully vaccinated.
Brandal et al, Eurosurveillance
Among 117 party attendees in Norway, 96% were fully vaccinated prior to the exposure event. Despite the high vaccination rate, 74% became infected with Omicron after the event.
It took between 0-8 days for individuals to develop symptoms after being exposed.
Since there was a well-defined exposure event, researchers were able to use this to estimate the incubation period of the Omicron variant.
They found that most individuals will develop symptoms between 3-4 days after exposure to the virus.
The incubation period for symptomatic cases ranged from 0 to 8 days with a median of 3 days (interquartile range: 3−4).
Brandal et al, Eurosurveillance
According to a study in Norway, the Omicron variant takes around 3-4 days to show symptoms for most people.
The most common symptoms were cough, runny or stuffy nose, fatigue, and sore throat.
Symptoms were generally mild. There were no reports of anyone having to go to the hospital. However, the high vaccination rate here may have played a role in preventing severe cases.
Cough was the most common symptom found in an Omicron outbreak in Norway. This was followed by runny nose, fatigue, and sore throat.
Study Figures
This chart shows when individuals developed symptoms after being exposed to Omicron. In this particular outbreak, most individuals were exposed during a Christmas party, as indicated by the black arrow. Most people showed symptoms around 3 days after the party.
Key Takeaway
The Omicron variant can reinfect those vaccinated against COVID-19. In this particular outbreak, nearly everyone was vaccinated. Yet still, most eventually came down with the omicron variant after being exposed.
This study was one of the first studies that documented how easily and quickly the omicron variant can spread.
The evidence here also provides valuable insights on the symptoms we can expect with Omicron. Nearly everyone will develop a cough and runny nose. Loss of taste and smell are relatively rare with Omicron. While symptoms were generally mild, the high vaccination rate may have played a role in preventing severe infections and hospitalizations in this particular case.
The preliminary results of our outbreak investigation indicate that the SARS-CoV-2 Omicron VOC is highly transmissible among fully vaccinated young and middle-aged adults.
Brandal et al, Eurosurveillance
Visual Abstract
A study in Norway found that the Omicron variant can infect fully vaccinated individuals. In this study, the omicron COVID-19 variant had an incubation period of 3 days. The top symptoms were cough, runny nose, fatigue, and sore throat.