Portugal Colonial - Moderna says US refusing to review mRNA-based flu shot

The move comes as the current iteration of the FDA has called for a reconsideration of approval procedures for certain vaccines, including for influenza -- proposed federal policy changes under President Donald Trump that have triggered widespread alarm among public health and medical professionals.

Moderna, a US company, said the agency's top vaccine regulator, Vinay Prasad, wrote in a letter that Moderna's clinical trial was not "adequate and well-controlled," and had not tested its experimental shot against the best product on the market.

In the large trial Moderna had compared its new vaccine with Fluarix, an approved flu shot from the company GSK.

Moderna said the rejection was "inconsistent with previous written communications" with the FDA branch that regulates biological products, including vaccines, known by the acronym CBER.

The decision "did not identify any safety or efficacy concerns with our product" and "does not further our shared goal of enhancing America's leadership in developing innovative medicines," Moderna CEO Stephane Bancel said in the statement.

"It should not be controversial to conduct a comprehensive review of a flu vaccine submission that uses an FDA-approved vaccine as a comparator in a study that was discussed and agreed on with CBER prior to starting."

Moderna said it had received a Refusal-to-File letter, which would indicate the application did not meet the requirements for substantive review. The company said it had requested a meeting to discuss the decision.

The letter did not identify any safety or efficacy concerns regarding the mRNA vaccine, said Moderna, which added the shot was accepted for review in the European Union, Canada and Australia.

During his first term Trump called mRNA technology a "modern-day miracle."

It was used during the Covid-19 pandemic to swiftly develop an immunization against the fast-spreading illness, and was credited with saving millions of lives.

Vaccines against Covid-19 are considered safe and effective by global health authorities, and protect against the most severe forms of the infection.

But in his second term, Trump has appointed Robert F. Kennedy Jr as his health chief, and the long-time vocal vaccine skeptic has spent the past year reshaping federal health agencies in his image.

That has meant spreading false information and sowing doubt about the safety and efficacy of vaccines widely known to be safe, and upending the pediatric immunization schedule.

Notably, Kennedy cut off federal research grants that funded mRNA development.

F.Ferraz--PC