- The Omicron variant is spreading faster than the Delta variant, a new mathematical analysis revealed.
- However, it is not clear whether this is due to it being more contagious, or being able to evade immunity.
- Research is in progress and scientists will have more answers this month.
The Omicron variant of the Covid-19 virus is spreading twice as quickly as the Delta variant, according to a preliminary analysis published on Friday.
Ever since the variant's discovery, scientists have said that it showed signs of higher transmissibility (the ability to spread fast within communities). This has been based on the rapid rise in cases (particularly in Gauteng, where the outbreak began), sequencing data, and the constellation of mutations in the spike.
The latest mathematical analysis adds support to this concern.
The Delta variant was responsible for driving SA's third wave of cases and was behind the surge in cases in multiple countries worldwide. However, it's not clear yet whether Omicron will overtake Delta as the predominant variant.
Scientists are still learning more about the variant and have said that their studies will take some time, but that results can be expected this month.
Omicron has been found in more than 30 countries, according to the World Health Organization.
Determining the R value
The latest analysis included involvement by scientists of the South African Covid-19 Modelling Consortium team. It was led by Carl Pearson, a mathematical modeller at the London School of Hygiene and Tropical Medicine.
The researchers looked at Covid cases across SA's nine provinces and estimated the variant's R value (a measure of a disease's ability to spread). Omicron's R value was found to be nearly 2.5 times as high as that of Delta's.
Tom Wenseleers, an evolutionary biologist at the Catholic University of Leuven in Belgium, told Nature that, based on the data, it is estimated that Omicron can infect three to six times as many people as Delta.
Pearson said on Twitter that he hopes that researchers globally will be able to use the team's findings to adequately prepare for an increase in cases this month.
Still early doors
The results have not yet been published in a peer reviewed journal. The team cautioned that research on how Omicron impacts the behaviour of the virus is still ongoing.
There is still uncertainty regarding the extent to which the variant can escape immunity, for example, the authors wrote.
Pearson told the New York Times that researchers aren't sure whether Omicron's rapid spread is primarily due to its contagiousness, or an ability to evade the immune system.
He said: "It's possible that it might even be less transmissible than Delta."
It is also not clear whether the variant causes more severe disease than Delta.
The team tweeted on Sunday that Gauteng and Mpumalanga were in the fourth wave, and that six provinces were also showing an increase in infections.
Gauteng and Mpumalanga are both in a fourth wave (cases have reached >30% of peak incidence of the third wave). Six other provinces are in a sustained increase (EC, FS, KZN, LP, NW and WC). Go to https://t.co/2QVtFegzvJ to monitor cases in your region. @Dr_Groome pic.twitter.com/3x6tSeHMPY— South African COVID-19 Modelling Consortium (@saCOVID19mc) December 5, 2021
Omicron, risk of reinfection
In the same week, SA researchers provided the first epidemiological evidence that Omicron has the ability to evade immunity from prior infection, making many people in the country, who had already contracted Covid, vulnerable to reinfection, AFP reported.
"Recent reinfections have occurred in individuals whose primary infections occurred across all three waves, with the most having their primary infection in the Delta wave," tweeted Dr Juliet Pulliam, director of the South African DSI-NRF Centre of Excellence in Epidemiological Modelling and Analysis.
The team is now researching Omicron's ability to escape vaccine-induced immunity. Many experts believe that, while the vaccines may not be able to offer strong protection against infection, it will continue to protect against hospitalisation and death.
Booster doses, however, will likely be needed for those at high-risk of severe illness, such as people aged 60 years and older and those with immuno-compromised conditions. This offer was recently opened to the latter group in December, as well as to healthcare workers, who received their first J&J dose as part of the Sisonke study.
The South African Health Products Regulatory Authority (Sahpra) is currently reviewing Pfizer's application for the approval of a booster dose for the rest of the population, aged 18 years and older.