Medical and public health officials are concerned—and puzzled—by the increasing...Leer más
Two new studies have suggested that the B.1.1.7 variant of SARS-CoV-2 is more transmissible than other strains but found no evidence to suggest it led to more severe disease or caused worse symptoms.
One of the studies found no evidence that B.1.1.7, sometimes known as the Kent or UK variant, increased the risk of developing long COVID compared to other variants.
An observational study, published in The Lancet Infectious Diseases, drew on data from 496 patients with COVID-19 at University College London Hospital and North Middlesex University Hospital between November 9 and December 20, 2020.
Among 341 patients who had their viral genomes sequenced, 58% had the B.1.1.7 variant and 42% had another strain.
The researchers found that 36% of B.1.1.7 patients became severely ill or died compared with 38% of those with another variant.
A further analysis of 289 patients found that those with B.1.1.7 were no more likely to experience severe disease after accounting for other factors, such as sex, age, ethnicity, and underlying conditions.
Also, those with B.1.1.7 were no more likely to die than patients with a different variant, with 16% of B.1.1.7 patients dying within 28 days compared with 17% of those with a non-B.1.1.7 infection.
An analysis of swabs found that B.1.1.7 samples contained a higher viral load than those of other variants.
Dr Eleni Nastouli, from University College London Hospitals NHS Foundation Trust and the UCL Great Ormond Street Institute of Child Health, UK, said: “One of the real strengths of our study is that it ran at the same time that B.1.1.7 was emerging and spreading throughout London and the south of England.
“Analysing the variant before the peak of hospital admissions and any associated strains on the health service gave us a crucial window of time to gain vital insights into how B.1.1.7 differs in severity or death in hospitalised patients from the strain of the first wave.”
Commenting on the study for the Science Media Centre, Dr Julian Tang, honorary associate professor and clinical virologist at the University of Leicester, said the research had “finally debunked the idea that the B.1.1.7 variant causes more severe disease”.
However, Dr Nicholas Davies, an evolutionary biologist and epidemiologist at the London School of Hygiene & Tropical Medicine, said community-based studies in England, Scotland, and Denmark had found that infection with the B.1.1.7 variant was associated with a higher overall risk of mortality and hospital and ICU admissions.
“This study focuses on outcomes among a different group of people, namely individuals who are already hospitalised with COVID-19,” he said. “Overall, the evidence suggests that B.1.1.7 is more likely to land you in the hospital than pre-existing variants of SARS-CoV-2, but once in the hospital there are no substantial differences in outcomes – or at least none that are statistically resolvable for now, given the limitation of low sample sizes.”
A separate study, published in The Lancet Public Health, analysed self-reported data from 36,920 users of the COVID Symptom Study app who tested positive for COVID-19 between September 28 and December 27, 2020.
Test results and symptom reports submitted through the app were combined with surveillance data to examine associations between the regional proportion of B.1.1.7 infections and symptoms, disease duration, reinfection rates, and transmissibility.
The analysis found no statistically significant differences between symptoms among people with B.1.1.7 and those with other variants. Neither was there any evidence of differences in the total number of symptoms experienced.
The proportion of people who went on to develop long COVID was not statistically different between the B.1.1.7 cohort and those with other variants.
The researchers also reported that there was no evidence that the frequency of reinfection was higher for the B.1.1.7 variant than for preexisting variants. They concluded that it was therefore likely that current COVID-19 vaccines would remain effective against the B.1.1.7 variant.
However, the researchers found that B.1.1.7 increased the overall R number by 1.35 times compared with the original strain.
Dr Mark Graham, from King’s College London, who led the analysis, said: “The wealth of data captured by the COVID Symptom Study app provided a unique opportunity to look for potential changes in symptoms and length of illness associated with the B.1.1.7 variant.
“Reassuringly, our findings suggest that, despite being more easily spread, the variant does not alter the type or duration of symptoms experienced and we believe current vaccines and public health measures are likely to remain effective against it.”
The authors acknowledged limitations in their research, including the use of self-reported data from people who had downloaded an app.
Writing in a linked comment, Dr Britta Jewell, from Imperial College London, who was not involved in the research, said: “This study adds to the consensus that B.1.1.7 has increased transmissibility, which has contributed in large part to the sharp rise in cases in the UK over the study period and beyond, as well as ongoing third waves in European countries with growing burdens of B.1.1.7 cases.”
The authors of both studies acknowledged that their findings differed from some other investigations into the severity of the B.1.1.7 variant and called for more research and monitoring of new variants.
Genomic characteristics and clinical effect of the emergent SARS-CoV-2 B.1.1.7 lineage in London, UK: a whole-genome sequencing and hospital-based cohort study. Published:April 12, 2021. DOI:https://doi.org/10.1016/S1473-3099(21)00170-5
Changes in symptomatology, reinfection, and transmissibility associated with the SARS-CoV-2 variant B.1.1.7: an ecological study. Published:April 12, 2021. DOI:https://doi.org/10.1016/S2468-2667(21)00055-4
Créditos: Comité científico Covid