On Thursday, British scientists released the kind of news everyone’s been dreading as we head into winter—a new, more infectious offshoot of the Delta variant appears to be spreading quickly across Britain.
A study from Imperial College found that the Delta subvariant—known to virologists as AY.4.2—accounted for around 12 percent of thousands of samples gathered in a recent British government survey, which is around 2.8 percent higher when compared to the figures from last month.
It’s previously been suggested that AY.4.2 could be as much as 15 percent more transmissible than the dominant Delta variant, which would make it the most infectious coronavirus strain since the pandemic began.
However, the Imperial scientists say they believe the variant’s spread might not be bad news for one crucial reason—it appears to cause significantly less symptomatic disease. Of the AY.4.2 samples gathered in government survey, only a third had the classic COVID symptoms, whereas half of patients with the original Delta experience those symptoms.
“It is preferentially appearing to be more transmissible,” Imperial epidemiologist Paul Elliott told reporters. “Why it is more transmissible we don’t know. It does seem to be less symptomatic, which is a good thing.”
However, other experts said it’s way too soon to say how the spread of AY.4.2 will change the course of the pandemic. While fewer symptoms could mean that fewer people get seriously ill, it could also mean that infected people go about their business without getting tested.
Prof. Christl Donnelly, another one of the Imperial researchers who worked on the report, said: “If it is less likely to be symptomatic, then it means it gets tested for less, and people may be out... On the other hand, if they are not coughing it might be spreading less far in distance.”
Simon Clarke, associate professor in cellular microbiology at the University of Reading, suggested that the apparently lower rate of symptomatic disease could be skewed by demographics.
“What the data doesn’t tell you is who those infections are in,” Clarke said. “So if they’re in younger people, or if they’re in a community that has a higher than average vaccine uptake, that might account for things.”
Whatever effect the new variant has, the research made one thing clear—vaccines are working, and booster shots are becoming crucial. The study found that the risk of infection was around three times lower in people who have had received a third dose compared to those who have had two. For over-fifties, a third dose reduced the infection risk by around half.
Jenny Harries, chief executive of the British government’s Health Security Agency, said in a statement that the study “provides another reminder of the effectiveness of the vaccines against COVID-19. As we approach winter, it is vital that everyone eligible comes forward for their jabs—whether that’s their first dose, second, or a booster.”