Health experts across the globe are remaining vigilant over Omicron BA.5, the coronavirus strain that is currently outpacing other variants in infection and has become the dominant strain in the US and abroad.
Ominously, it also has the ability to reinfect people within weeks of contracting the virus.
Andrew Roberston, the chief health officer in Western Australia, told News.com.au that although previously convetional wisdom held that most people would retain a certain level of protection against reinfection if they were vaccinated or had retained some level of natural immunity due to a recent contraction of the virus, this has not proven the case with the most recent strain.
“What we are seeing is an increasing number of people who have been infected with BA.2 and then becoming infected after four weeks,” the doctor explained during an interview with the news outlet.
“So maybe six to eight weeks they are developing a second infection, and that’s almost certainly BA.4 or BA.5.”
The ability for strains BA.4 and BA.5 to reinfect individuals who would, in previous waves of Covid-19, have had stronger immunity has led some experts to start calling this latest strain the most transmissible yet.
“They’re taking over, so clearly they’re more contagious than earlier variants of omicron,” said David Montefiori, a professor at the Human Vaccine Institute at Duke University Medical Center, in an interview with NBC News.
Federal estimates released by the US Centers for Disease Control and Prevention show that BA.5 has now taken over as the dominant strain in America, currently accounting for 83.1 per cent of cases.
And although the average number of new cases that the US records each day is currently low, at around the 40,000 mark, experts fear that a combination of home testers not reporting positive cases, a closure of government-funded testing centres and an uptick in states stopping their daily data updates has led to a less accurate picture of how much this new strain is actually penetrating the nation.
A recent study published in Science has confirmed the troubling reality that many may have already been experiencing anecdotally with multiple back-to-back reinfections: these two new subvariants evade protection from previous infections and vaccines.
Immunology professor Danny Altmann, co-author of the Science paper alongside Rosemary Boyton, a professor of immunology and respiratory medicine, discussed the findings from their research in a recent op-ed.
They noted that, contrary to a popular held belief that vaccines and previous infection would provide “a wall of immunity”, nations are instead experiencing “wave after wave of new cases”.
In the study, Professor Altmann explains how they followed individuals who were triple vaxxed and those who suffered breakthrough infections during earlier Omicron waves.
“This lets us examine whether Omicron was, as some hoped, a benign natural booster of our Covid immunity,” he wrote in The Guardian. “It turns out that isn’t the case.
“Most people – even when triple-vaccinated – had 20 times less neutralising antibody response against Omicron than against the initial ‘Wuhan’ strain,” Professor Altmann said, noting that, importantly, “Omicron infection was a poor booster of immunity to further Omicron infections.
“It is a kind of stealth virus that gets in under the radar,” he said, emphasising that “even having had Omicron, we’re not well protected from further infections”.
Mr Altmann’s research seems to confirm other recent studies warning of the new subvariants’ ability to evade protection from previous immune-building precautions; namely vaccination and natural immunity.
Research published in Nature out of Columbia University suggests that BA.4 and BA.5 are four times more resistant to antibodies from vaccines than BA.2, a subvariant that became the dominant strain in the US in April, replacing the original strain that had driven the winter wave across the country.
Though experts believe that these current strains will likely fuel new waves, they did note that vaccines will provide partial immunity and can still protect against potentially more severe infections.
“Our data suggest that these new Omicron subvariants will likely be able to lead to surges of infections in populations with high levels of vaccine immunity as well as natural BA1 and BA2 immunity,” Dr Dan Barouch told CNN.
“It is likely that vaccine immunity will still provide substantial protection against severe disease with BA4 and BA5.”
Dr Barouch was one of the co-authors on a separate paper, published with The New England Journal of Medicine, which found that there was a three-fold reduction of neutralising antibodies from vaccines and infection against BA.4 and BA.5, which was substantially lower than BA.1 and BA2.
Because of this, vaccines that many received in the past 18 months will likely need not only a boost, but an update.
The US Food and Drug Administration has recommended that Covid vaccine makers, namely Pfizer and Moderna, begin modifying what they currently have on offer so that their booster shots can more accurately target the BA.4 and BA.5 variants and estimated that these shots could become available as early as mid-fall.
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