Brazil virus variant found to evade natural immunity
Studies ‘urgently needed’ to check efficacy of current vaccines against strain, researchers say
Anna Gross and Clive Cookson in London
The P.1 Covid-19 variant that was identified in Brazil is about twice as transmissible as some other virus strains and is more likely to evade the natural immunity usually conferred by prior infection, according to an international study.
The research, conducted by a UK-Brazilian team of researchers from institutions including Oxford university, Imperial College London the University of São Paulo, found that the P.1 variant was between 1.4 and 2.2 times more transmissible than other variants circulating in Brazil.
It was also “able to evade 25-61 per cent of protective immunity elicited by previous infection” with another variant, the researchers found, a sign that current vaccines could also be less effective against it.
International concern about the P.1 variant has escalated as more than 25 countries have detected the variant, including Belgium, Sweden and the UK, which has identified six cases.
The scientists are expected to release a paper describing the research on Tuesday. The study has not yet been peer reviewed.
Dr Nuno Faria, lecturer at Imperial College and associate professor at Oxford, the lead author on the study, said: “We can confidently say that P.1 has altered the epidemiological characteristics of the virus in Manaus but whether that is true in other settings we don’t yet know.
He added: “We have no evidence so far that P.1 won’t respond to vaccines, at least for preventing serious disease.”
Whether P.1 or another variant, B.1.1.7, which was first identified in the UK, is more transmissible “is a really important question that needs to be addressed”, Faria said.
The researchers have dated the emergence of the P.1 variant to November 6, 2020, around one month before cases began to surge for the second time in the Brazilian city of Manaus. They found that the proportion of cases classified as P.1 in Manaus increased from zero to 87 per cent in the space of seven weeks.
The paper concluded: “Our results further show that natural immunity waning alone is unlikely to explain the observed dynamics in Manaus, with support for P.1 possessing altered epidemiological characteristics.”
“Studies to evaluate real-world vaccine efficacy in response to P.1 are urgently needed,” it added.
The researchers also found that infections were 10 to 80 per cent more likely to result in death in Manaus after the emergence of P.1. However, the authors cautioned that it was not possible to determine whether this meant the variant was more lethal or whether it was a result of increased strain on the city’s healthcare system, or both.
The P.1 variant has over 17 mutations, which alter its genetic sequence from the virus originally identified in Wuhan, including 3 changes to the spike protein that it uses to enter human cells.
Researchers in Brazil have been using genetic sequencing technology developed by Oxford Nanopore in the UK to identify and track the variant. The technology was first used in Brazil during the Zika outbreak in 2015.
Dr Leila Luheshi, director of applied and clinical markets at Oxford Nanopore, told the Financial Times that while the B.1.1.7 variant in the UK had similar properties of high transmissibility to P.1 — it is thought to be around 1.5 times as transmissible as variants that preceded it — there was no evidence to date that it evaded past natural immunity in the same way. Studies have also shown that current vaccines retain their efficacy against B.1.1.7.
Luheshi said that “because [P.1] has these mutations around the spike . . . the hypothesis is that the vaccine will be less effective”. But she added that there is not yet definitive evidence to support this theory.
0 comments:
Publicar un comentario