Pfizer's New mRNA Flu Vaccine Outperforms Traditional Shot Against Predominant Strains

A Phase 3 study funded by Pfizer Inc. (NYSE:PFE) suggests that a nucleoside-modified messenger RNA influenza vaccine could offer stronger protection than traditional flu shots, marking a potential shift in how seasonal influenza is prevented.

Researchers reported that the experimental quadrivalent modRNA vaccine delivered higher efficacy against circulating flu strains, though it also produced more short-term reactions following vaccination.

The trial evaluated healthy adults ages 18 to 64 during the 2022–2023 flu season. In total, 18,476 volunteers were enrolled, with roughly half in each study arm.

Participants were randomly assigned to receive either the investigational modRNA vaccine or a licensed inactivated quadrivalent influenza vaccine that served as the control.

Also Read: Moderna’s mRNA Flu Vaccine Outperforms Standard Shots

The primary goal was to measure how well the modRNA shot reduced laboratory-confirmed influenza cases accompanied by influenza-like illness at least two weeks after vaccination.

Researchers also assessed immune responses, short-term side effects, and serious adverse events over several months.

According to the results, the modRNA vaccine achieved a relative efficacy of 34.5% compared with the licensed flu vaccine.

That figure was based on 57 confirmed influenza-like illness cases among modRNA recipients and 87 cases among those who received the control shot.

The outcome met the criteria for both noninferiority and superiority.

Most documented cases were driven by A/H3N2 and A/H1N1 strains, with almost no activity from B strains during the season.

The antibody response measured by hemagglutination inhibition showed noninferiority against influenza A strains but did not reach that threshold for influenza B strains, aligning with the low circulation of B viruses.

While both vaccines produced mostly mild to moderate reactions, the modRNA candidate showed higher reactogenicity.

Local reactions occurred in 70.1% of modRNA recipients versus 43.1% in the control group.

Systemic symptoms were reported in 65.8% of the modRNA group compared with 48.7% of control participants.

Fever was more common in the modRNA arm as well, occurring in 5.6% of vaccinated individuals versus 1.7% in the comparator group.

Researchers concluded that the modRNA vaccine demonstrated statistically superior efficacy and stronger immune responses to predominant A strains, though at the cost of higher reactogenicity.

Last week, Merck & Co. Inc. (NYSE:MRK) agreed to acquire Cidara Therapeutics, Inc. (NASDAQ:CDTX) for $221.50 per share in cash, for a total transaction value of approximately $9.2 billion.

Cidara's lead candidate, CD388, consists of a small molecule neuraminidase inhibitor stably conjugated to a proprietary Fc fragment of a human antibody designed to prevent influenza A and B.

PFE Price Action: Pfizer stock is up 3.13% at $25.18 at publication on Friday.

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