Washington, July 22 The latest surge in global Covid cases, majorly driven by the Omicron sub-variant BA.5, may be causing increasing reinfections, meaning more people are catching Covid-19 for the second or third time, according to a media report.
Data from the gene sequencing company Helix, however, showed that these reinfections do not seem to be happening more rapidly, CNN reported.
For the analysis, the company included 300,000 infections since March 2021 and showed that reinfections almost doubled to 6.4 per cent during the BA.5 wave in July from 3.6 per cent during the BA.2 wave in May.
In April, during the BA.2 wave, the average time between positive Covid-19 tests for the same person was about 230 days; by July, it was about 270 days, or about nine months, the report said.
"The most recent data we had pulled showed that the fraction of all infections that are reinfections have increased quite a bit. There was a jump," Shishi Luo, associate director of bioinformatics and infectious disease at Helix, was quoted as saying.
The reinfections are the result of waning immunity, broad spread and mutations to BA.5, Luo said.
Further, the data showed that on average, people who are getting reinfected now were last infected about nine months ago.
But, recently Andrew Roberston, the chief health officer in Western Australia, said the BA.5 sub-variant can reinfect 'within weeks'.
"What we are seeing is an increasing number of people who have been infected with BA.2 and then becoming infected after four weeks," Roberston was quoted as saying to News.com.au.
"So maybe six to eight weeks they are developing a second infection, and that's almost certainly BA.4 or BA.5," he added.
This may be explained by a recent study, published in the journal Science, which showed that Omicron provides a poor natural boost of Covid immunity against reinfection even with Omicron and also in people who are triple-vaccinated.
Researchers at the Imperial College London called the BA.5 "an especially stealthy immune evader".
"Not only can it break through vaccine defences, it looks to leave very few of the hallmarks we'd expect on the immune system - it's more stealthy than previous variants and flies under the radar, so the immune system is unable to remember it," said Professor Danny Altmann, from Department of Immunology and Inflammation at Imperial.
BA.5 is currently the most dominant strain in circulation, globally, reported from 100 countries, the World Health Organization (WHO) said in its weekly report.
Representing 53.59 per cent of all Omicron sequences, BA.5 is continuing to drive an increase in cases, hospitalisations and ICU admissions, the WHO said, based on the data downloaded from open access data platform GISAID on July 18.
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