Pfizer and BioNTech's COVID/flu vaccine hits a hurdle

Pfizer and BioNTech have been among the leaders in the race to bring a combined COVID-19 and influenza vaccine to market, but have stumbled in the final straight.

The companies reported mixed results in their phase 3 trial of their mRNA vaccine, which includes antigens for influenza A and B, as well as the SARS-CoV-2 virus that causes COVID-19, and have said they will need to tweak the formulation.

The problem is a lower-than-expected antibody response for influenza B in the 8,000-subject study, which was designed to show non-inferiority to Pfizer and BioNTech's Comirnaty COVID-19 jab, as well as a commercially available flu vaccine, and demonstrate safety.

Last October, the companies reported "robust" antibody and T-cell responses against the viruses, in the same ballpark as approved vaccines, with a safety profile similar to Comirnaty in a phase 1/2 trial that prompted them to start a phase 3 programme.

In a joint statement, Pfizer and BioNTech said they are "evaluating adjustments to the candidate and will discuss next steps with health authorities." It's not clear yet what the delay to the programme could be, but if a new phase 3 trial is needed – as seems likely if the constituents of the vaccine need to be modified – it could be lengthy.

Pfizer's head of vaccine R&D, Annaliesa Anderson, said the company remains "committed to developing vaccines that will reduce the burden of respiratory diseases and believe that combination vaccines are the most efficient way to do this."

The slip-up hands an opportunity for mRNA vaccine rival Moderna to build a lead in the combined COVID-19/flu vaccine category.

In June, Moderna said its candidate met its objectives in a phase 3 trial, stimulating higher immune responses against influenza and SARS-CoV-2 than the licensed flu and COVID vaccines used as comparators in the study, which the company said could lead to approval in late 2025 or 2026.

Moderna's study looked at the vaccine in adults aged 50 and older, while Pfizer/BioNTech's trial focused on adults aged 18 to 64.

Other rivals, meanwhile, include Sanofi/Novavax, which are developing non-mRNA candidates under the terms of a $1.2 billion alliance agreed in May.

BioNTech's chef executive, Uğur Şahin, said: "The insights gained from this combination vaccine trial are highly valuable and will play a crucial role in guiding the further development of […] our combination vaccine programme against influenza and COVID-19."