Two new studies suggest that the B.1.1.7 coronavirus variant, which was first identified in the United Kingdom, is more transmissible, but the variant does not appear to affect disease severity in someone who gets Covid-19. The new findings clash with separate research that previously suggested the variant may be tied to a higher risk of dying from Covid-19.
One of the new studies, published on Monday in The Lancet Infectious Diseases, found no evidence in a sample of hospitalized patients that the B.1.1.7 variant is associated with severe Covid-19. However, the variant was associated with increased viral load, which supports the growing evidence that it is more easily transmissible.
The other study, also published on Monday in The Lancet Public Health, found no statistically significant association between the B.1.1.7 variant and the types or duration of Covid-19 symptoms people said that they experienced.
The Lancet Infectious Diseases study included data on 496 people who were admitted to hospitals in London and tested positive for coronavirus infection. Nose and throat swab samples were collected from the patients between Nov. 9 and Dec. 20.
Among those samples, 341 underwent genome sequencing. The sequence data showed that 198 of the patients, or 58%, had infections caused by the B.1.1.7 variant while the others were cased by other strains of the coronavirus. The researchers found no difference in severe disease or death between the variant and other strains.
The data showed that 36% of patients in the study with the B.1.1.7 variant infection experienced severe illness or death compared with 38% of those with non-B.1.1.7 infections. For death specifically, 16% of with the B.1.1.7 variant infection died within 28 days compared with 17% of those with non-B.1.1.7 infections, the researchers found.
But the researchers identified increased viral load among the B.1.1.7 patients.
Overall, "patients with B.1.1.7 were younger and had fewer comorbidities than those with non-B.1.1.7 infection, possibly representing the widespread and potential increased transmission of this variant in the community or differences in probability of hospital admission, which we were not able to explore in this hospital-based cohort," the researchers wrote in their study.
"Finding B.1.1.7 more commonly in younger versus older individuals gives a subtle hint of more severe disease if patients with B.1.1.7 are hospitalised more often compared with patients with other lineages, although difference in disease severity by B.1.1.7 was not found in this hospitalised cohort in the main analysis," the researchers wrote.
The Lancet Public Health study included data on 36,920 people who reported testing positive for Covid-19 and logged their symptoms into the COVID Symptom Study app between September 28 and December 27. The app — designed by designed by researchers at King's College London, Guys and St Thomas’ Hospitals and the tech company Zoe Global Limited — helps track the spread of Covid-19 and the range of symptoms experienced.
The study’s authors, based in the UK and the United States, analyzed the data reported in the app along with Covid-19 surveillance data for the UK. The analysis showed that the prevalence of the B.1.1.7 variant in certain regions and over time was not associated with changes in the Covid-19 symptoms reported in the app nor the duration of symptoms.
The researchers found that the rate of coronavirus reinfections was low — with 0.7% of app users who reported a positive Covid-19 test, testing positive again after 90 days — and there was no evidence of increased reinfection rates associated with the B.1.1.7 variant.
The researchers did not have data on risk of dying from Covid-19 and most of the app users get tested only when they have symptoms, so there were relatively few asymptomatic infections in the data. Yet the researchers found a "multiplicative increase" in the reproduction number of the B.1.1.7 variant, suggesting it can spread more easily.