Moderna, Pfizer say COVID jabs work against BA.2.86

Moderna and Pfizer have both said that updated versions of their COVID-19 vaccines work against the highly mutated BA.2.86 variant, also known as Pirola, which is being closely watched by health authorities around the world.

Pirola is considered to be one of the most worrying new strains of the coronavirus since Omicron emerged in late 2021, although it hasn't yet been deemed a variant of concern (VOC) by the World Health Organization (WHO).

Pirola has more than 30 mutations in its spike protein – the antigen used to stimulate an immune response in COVID-19 vaccines – which led to concerns that the current generation of shots may lack efficacy.

It's encouraging, then, that Moderna's mRNA-1273.715 vaccine, which has already been filed for approval with the FDA, generated a strong immune response against Pirola, including a nearly nine-fold increase in neutralising antibodies against the variant.

The data on Pfizer and partner BioNTech's vaccine is earlier stage, coming from a preclinical study in mice, but still supports the idea that the new version of its Comirnaty shot expected to be used this autumn will provide protection.

Both the new vaccines were developed to target the XBB.1.5 subvariant of Omicron, and Pfizer/BioNTech's has already been cleared in the UK and recommended for approval in the EU.

Last month, Moderna also said that mRNA-1273.815 generated a strong immune response against the EG.5 (Eris) and FL.1.5.1 (Fornax) variants – currently accounting for around 22% and 15%, respectively, of US cases, according to the Centers for Disease Control and Prevention (CDC).

That suggests that it can tackle all three expected circulating variants of SARS-CoV-2 during the upcoming vaccination season, said Moderna. Pfizer, meanwhile, has also indicated that its shot is effective against Eris.

Studies in the US, however, have suggested that vaccination and previous infection with COVID-19 seem to be fairly effective at protecting against Pirola, backing up earlier testing in China and Sweden.

The variant – which does seem more able to infect people previously infected with COVID-19 – has now been identified in Denmark, Israel, Switzerland, South Africa, the UK, and the US, with 29 cases identified worldwide, according to the most recent CDC data.

Some researchers have suggested that close attention should also be paid to Fornax, as that is also highly mutated and may be more able to evade the antibodies stimulated by current vaccines.