Omicron is causing consternation around the world, with the variant causing an exponential increase in Covid cases in South Africa. Still, with only 42 cases confirmed in the UK so far, and most European countries seeing numbers in the double rather than the triple, could this be a tentative sign that the variant may not be successful? to set up outside southern Africa? Ultimately, it is too early to tell.
One of the problems is that there are important differences which make it difficult to compare situations in South Africa and beyond.
Professor Rowland Kao, an epidemiologist at the University of Edinburgh and a member of the Spi-M modeling group, noted that different variants of Covid are circulating in South Africa and the country uses different vaccines than those used in Britain .
Besides the Pfizer / BioNTech vaccine, he used the Janssen vaccine – not yet used in the UK – and suspended the use of the Oxford / AstraZeneca vaccine. Kao said some differences could help Britain, such as the longer interval between vaccine doses.
“The fact that we had an early deployment of vaccines and then many people infected [with Covid] can also be useful in broadening the spectrum of the immune response, and this can again mean that we have more protection than [South Africa], ” he said.
With Covid already ‘hot’ in the UK and some European countries, it is difficult to detect the first signs of Omicron’s impact. Before the new variant was detected, cases of Covid in South Africa were very low, meaning its impact became clear at an early stage.
Dr Michelle Groome, of the South African National Institute of Communicable Diseases (NICD), said new cases of Covid had risen from a weekly average of around 300 a day to 1,000 last week, and more recently at 3,500.
In contrast, the UK has seen a large number of cases per day – 53,945 on Thursday alone – with numbers fluctuating by several thousand from day to day. If Omicron leads to an increase in cases, it may take longer for cases to emerge from this data alone.
However, case numbers are not the only source available to scientists. One approach that experts are using to investigate Omicron’s presence in the UK is to look at test results for the coronavirus S gene in samples positive for Covid.
Omicron has a mutation which means it is negative on such tests, as it was for the Alpha variant, but not Delta, which means the test can give a quick – although inconclusive – indication of the presence from Omicron.
In a Twitter threadProfessor Nick Davies of the London School of Hygiene & Tropical Medicine noted that in the five days leading up to November 28, there had been an increase in S gene target failure in community testing data in England from about 0.1% to about 0.3%.
Davies said about half of PCR tests in the community are processed by labs that use such a test, although the Guardian understands there may be some prioritization of cases in areas where Omicron has already been found. .
While Davies found the results only amounted to about 60 more samples that tested negative for the S gene than would otherwise have been expected, he said the excess was likely due to the Omicron cases and suggested that the numbers would likely increase.
However, it is not yet known whether these cases are due to imported infections or related to transmission within the community. “English scientists will therefore be closely monitoring this data flow over the next few days and weeks to understand what is going on,” Davies wrote.
Others have also pointed out that the situation in the UK is still in its early stages, but there is cause for concern. “There has been at least one large-scale event in Scotland – indicating potential for rapid spread,” Kao said, adding that the S gene test results are part of the evidence suggesting the UK is starting. also to see signs of an exponential increase.
Kao said, “There is good reason to believe that this is already spreading at a good pace. But what we don’t know yet is whether or not this will continue, and also whether it will lead to a more sustained increase in hospitalizations and deaths. ”