New Delhi, Jun 13 (IANS): US drugmaker Pfizers and British pharma major GSK are likely to face significant competition in the respiratory syncytial virus (RSV) vaccine market, according to a report on Tuesday.

GSK's novel vaccine, Arexvy, approved by the US FDA in May, becomes the first RSV vaccine authorised for use in America.

It was recently also approved by the European Commission (EC) for the prevention of lower respiratory tract infections (LRTI) caused by RSV in adults 60 years of age and older, making it the first RSV vaccine available across the EU.

Despite these landmark approvals, GSK's dominance in the untapped RSV vaccine space is under threat by Pfizer which is in hot pursuit for market share of its own RSV vaccine Abrysvo, said the report by GlobalData, a leading data and analytics company.

"While Arexvy was first to gain US approval, which marked the first time a vaccine was authorised for use against RSV in any population, anywhere in the world, Pfizer's Abrysvo was approved by the FDA quickly after, allowing sufficient time for both vaccines to be available for US launch around the same time this fall, prior to the winter RSV season," said Nancy Jaser, Pharma Analyst at GlobalData, in a statement.

"Therefore, GSK is not likely to experience a significant first-mover advantage for market share in the US. However, Arexvy may still benefit from a first-mover advantage in the EU as Pfizer's Abrysvo has yet to gain approval for use by the EC. A decision is expected later this year," Jaser added.

While both vaccines demonstrated high efficacy in pivotal trials, Pfizer's vaccine has one critical advantage over Arexvy. Abrysvo is currently under review in the US as a maternal vaccine to protect infants against RSV right at birth.

The FDA's Vaccines Advisory Committee voted in favour of approving Abrysvo as a maternal RSV vaccine, the report said.

"Abrysvo will likely be the first approved RSV vaccine to protect infants worldwide, potentially leading to a higher market share than its competitors. It is currently the only vaccine candidate in late-stage development that targets multiple patient segments," Jaser said.

Further competition is expected from Moderna's RSV vaccine, mRNA-1345. Positive Phase III data in older adults were announced in January, while Moderna plans to file for US approval in the first half of 2023.

"mRNA-1345 is likely to be the first mRNA-based RSV vaccine to reach the market. As an RNA virus, RSV is capable of rapid mutation to escape attack by new pharmaceuticals. Novel RSV variants could emerge as a result, requiring adjustments to vaccine targets," Jaser said.

"Moderna's vaccine would likely see higher success in this situation, as the mRNA platform allows for quick modification of antigens to target potential new viral strains,a she noted.