It looks like Covid-19 is on the move again – how concerned should we be?

Hospitalisations with Covid-19 are up and are really the only reliable statistic with regards to Covid spread in Ireland. The HSE are not doing enough community PCR testing to offer any kind of definitive picture of what exactly the Sars-CoV-2 virus is up to on the ground here.

However, international agencies are still actively monitoring Covid-19 activity; they have spotted two new strains of the virus with some significant differences from the Omicron strain.

BA.2.86 is the latest strain to be identified. It has prompted the Centre For Disease Control (CDC) in the US to take the rare step of issuing a formal warning that the new strain could evade existing vaccines and interfere with the protection we get from natural immunity.

Unofficially labelled Pirola, the new strain is of particular concern because of its more than 30 mutations, which means it may behave very differently than previous versions of the virus. The last time we saw that number of mutations was when the Covid playing pitch was significantly altered from the Delta to the Omicron variant – a reflection of the serious differences between variants that led to the last major naming change of the virus by the World Health Organisation (WHO).

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What we’ll see in the weeks ahead is whether BA.2.86 takes hold or not. If it does, that will pose a new challenge

Last month, the WHO responded to the emergence of Pirola by declaring it a “variant under monitoring”. And some weeks before that it upgraded another new variant, EG.5 from a variant under monitoring to a variant of interest (VOI). In a new risk evaluation, the WHO placed EG.5 alongside XBB.1.5 and XBB. 1.6, which are also sub variants in the Omicron family tree. While EG.5 (unofficially named Eris) appears to be more infectious, there is little evidence to date to suggest it causes more severe illness.

But the CDC risk assessment of Pirola is more worrying: “BA.2.86 may be more capable of causing infection in people who have previously had Covid-19 or who have received Covid-19 vaccines,” it says.

So with 36 new mutations, many of them altering the spike protein on the Sars-CoV-2 virus, Pirola is causing a level of unease among global experts. The journal Nature reports that many scientists see similarities between the emergence of BA.2.86 and that of Omicron, which rapidly spread around the world in late 2021.

What will these changes mean for the next version of the Covid-19 vaccine? Now predicted to be available between the middle and end of September, the boosters we will be offered once the campaign starts are designed to tackle the Omicron subvariant XBB.1.5. Unlike last year’s formulation, a mixed bivalent vaccine, the upcoming vaccine will be monovalent, specifically designed against XBB.1.5. This vaccine is expected to work against EG.5.

But for now, the new vaccine’s ability to combat the BA. 2.86 variant is not known. The hope is that it will offer some protection against serious illness and hospitalisation but some experts remain fearful of how easily spread the variant will become. Infectious disease expert Dr Peter Chin- Hong from the University of San Francisco says “BA.2.86 is so different that people worry that the vaccine in the fall won’t be a perfect match – but nevertheless, it will still protect people against serious disease.”

Dr Eric Topol, director of the Scripps Research Translational Institute in San Diego, said in a blog post that recent trends underscore how “the pandemic isn’t over.”

“What we’ll see in the weeks ahead is whether BA.2.86 takes hold or not. If it does, that will pose a new challenge, and make the ‘updated’ booster shots considerably less helpful than what was conceived when XBB.1.5 was selected as the target,” Topol wrote.

So watch out – a ‘Pirola Pirouette’ could make Covid-19 more of a health challenge than we hoped for this winter.

muiris.houston@irishtimes.com