In a groundbreaking phase three trial, recently shared in the New England Journal of Medicine, researchers examined the efficacy of a new flu vaccine involving over 18,000 participants aged 18 to 64.

The trial divided participants into two groups: one received the traditional flu vaccine, while the other was administered Pfizer’s innovative mRNA-based vaccine.

Results revealed that Pfizer’s mRNA vaccine demonstrated a 34.5% higher effectiveness in preventing influenza A compared to the standard flu shot.

Although not part of the study, Professor Archa Fox from the University of Western Australia praised the findings, stating, “The mRNA vaccine outperformed conventional flu vaccines.”

Statistics from the study showed that only 0.63% of individuals given the mRNA vaccine contracted the flu, in contrast to 0.95% of those who received the traditional flu vaccine.

The results are similar to a trial of another mRNA flu vaccine developed by Moderna, which showed a 26.6 per cent effectiveness increase compared to a standard vaccine.

However, there weren’t enough cases of influenza B in today’s study to determine the Pfizer vaccine’s effectiveness against that type of virus, and the mRNA jab was also linked to a higher rate of mild to moderate side effects.

“Lab tests suggested that the new vaccine may not be as effective against B strains,” Associate Professor Seth Cheetham from the University of Queensland said. 

“The mRNA vaccine was safe, but an elevated rate of side effects, such as headache and injection site pain, was detected compared to traditional vaccines.”

The level of severe side effects, though, was similarly low for both vaccines.

However, the phase three trial showed another limitation of the Pfizer vaccine: a lack of benefit for vulnerable elderly patients.

“Most crucially, it showed no significant benefit for adults over 65, the group most at risk from severe flu, highlighting that this is a promising step forward but not a complete solution for all,” molecular virologist Vinod Balasubramaniam said.

Vaccination rates against flu have dropped significantly in recent years in Australia, despite a surge in the number of cases of the potentially deadly illness.

Experts are hoping the development of mRNA vaccines, using similar technology to what was behind the successful COVID-19 vaccines, could lead to better protection against the virus.

“Manufacturing mRNA vaccines is significantly faster than traditional methods, which rely on growing the virus in eggs or cells, a process that can take six months or more,” Dr Emma Grant from La Trobe University said. 

“Faster production means vaccine strains can be selected closer to the flu season, reducing the risk of mismatch with circulating viruses.

“Moreover, as demonstrated with COVID-19 vaccines, mRNA technology can activate multiple arms of the immune system, including long-lived killer T cells that recognise multiple different influenza strains… 

“This capability moves us closer to the long-sought goal of a ‘universal’ influenza vaccine, one that provides broader and longer-lasting protection.”