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Pfizer Reiterates Commitment to Pandemic Preparedness

NEW YORK, NY, MAY 28, 2024 – Pfizer Inc. (NYSE:PFE) continues to closely monitor all developments regarding the circulation and outbreaks of the A/H5N1 virus. As part of the company’s broader pandemic preparedness efforts, in late 2023, Pfizer initiated a randomized Phase 1 study to evaluate the safety, tolerability, and immunogenicity of multiple doses of nucleoside-modified mRNA (modRNA) based pandemic influenza vaccine candidate (NCT06179446). 

The candidate being evaluated encodes the hemagglutinin (HA) antigen of a pandemic influenza strain from the A/H5 subtype, which may provide relevant information about the current circulating H5N1 viruses. Specifically, the vaccine candidate is designed to antigenically mirror the avian strain [H5, Clade] currently causing significant disease in birds and cows and recent case reports illustrating limited cross-over into humans. Data generated using a research assay from a subset of participants dosed in this program illustrate notable increases in antibody responses against this group of H5 influenza virus. 
Pfizer is encouraged by these early, preliminary results and, in the event of a request from health authorities, would be prepared to deploy the company’s capabilities to develop a vaccine for strategic stockpiles.
If a vaccine is needed in an emergency pandemic situation, Pfizer anticipates that the modRNA vaccine platform could be leveraged to rapidly provide a vaccine candidate targeting the specific pandemic influenza strain. Pfizer believes the mRNA platform is well-suited to respond in a pandemic given the flexibility, versatility, and agility of the technology, as well as the speed at which constructs can be developed and rapidly manufactured. As with all Pfizer investigational programs, studies will be advanced with scientific rigor and focus, and in close alignment with relevant health authorities.
About Pandemic Influenza
Influenza viruses are a group of RNA viruses which can cause contagious respiratory illness. Two types of influenza, A and B typically cause seasonal epidemics, while sporadic pandemics can be caused by influenza A viruses. According to the US Centers for Disease Control and Prevention , a flu pandemic is a global outbreak of a new flu A virus and flu pandemics happen when three things occur: 

    a new flu A virus emerges that can infect people easily, 
    the virus spreads in an efficient and sustained way, and
    the virus is one to which most of the world’s population do not have immunity.

About Pfizer: Breakthroughs That Change Patients’ Lives
At Pfizer, we apply science and our global resources to bring therapies to people that extend and significantly improve their lives. We strive to set the standard for quality, safety and value in the discovery, development and manufacture of health care products, including innovative medicines and vaccines. Every day, Pfizer colleagues work across developed and emerging markets to advance wellness, prevention, treatments and cures that challenge the most feared diseases of our time. Consistent with our responsibility as one of the world's premier innovative biopharmaceutical companies, we collaborate with health care providers, governments and local communities to support and expand access to reliable, affordable health care around the world. For 175 years, we have worked to make a difference for all who rely on us. We routinely post information that may be important to investors on our website at In addition, to learn more, please visit us on and follow us on X at @Pfizer and @Pfizer News, LinkedIn, YouTube and like us on Facebook at


The information contained in this release is as of May 28, 2024. Pfizer assumes no obligation to update forward‐looking statements contained in this release as the result of new information or future events or developments. 

This release contains forward-looking information about Pfizer’s investigational modRNA based pandemic influenza vaccine candidate, the modRNA platform and Pfizer’s pandemic preparedness efforts, including their potential benefits, that involves substantial risks and uncertainties that could cause actual results to differ materially from those expressed or implied by such statements. Risks and uncertainties include, among other things, the uncertainties inherent in research and development, including the ability to meet anticipated clinical endpoints, commencement and/or completion dates for our clinical trials, regulatory submission dates, regulatory approval dates and/or launch dates, as well as the possibility of unfavorable new clinical data and further analyses of existing clinical data; risks associated with early and preliminary data; the risk that clinical trial data are subject to differing interpretations and assessments by regulatory authorities; whether regulatory authorities will be satisfied with the design of and results from our clinical studies; whether and when biologic license applications may be filed in any jurisdictions for Pfizer’s modRNA based pandemic influenza vaccine candidate or for any other potential vaccine candidates; whether and when any such applications may be approved by regulatory authorities, which will depend on myriad factors, including making a determination as to whether the product's benefits outweigh its known risks and determination of the product's efficacy and, if approved, whether Pfizer’s modRNA based pandemic influenza vaccine candidate or any such other potential vaccine candidates will be commercially successful; decisions by regulatory authorities impacting labeling, manufacturing processes, safety and/or other matters that could affect the availability or commercial potential of Pfizer’s modRNA based pandemic influenza vaccine candidate or any such other potential vaccine candidates; uncertainties regarding the ability to obtain recommendations from vaccine advisory or technical committees and other public health authorities regarding Pfizer’s modRNA based pandemic influenza vaccine candidate or any such other potential vaccine candidates and uncertainties regarding the commercial impact of any such recommendations; uncertainties regarding the success of Pfizer’s pandemic preparedness efforts; disruptions in the relationships between us and our collaboration partners, clinical trial sites or third-party suppliers; the impact of COVID-19 on Pfizer’s business, operations and financial results; and competitive developments. 

A further description of risks and uncertainties can be found in Pfizer’s Annual Report on Form 10-K for the fiscal year ended December 31, 2023 and in its subsequent reports on Form 10-Q, including in the sections thereof captioned “Risk Factors” and “Forward-Looking Information and Factors That May Affect Future Results”, as well as in its subsequent reports on Form 8-K, all of which are filed with the U.S. Securities and Exchange Commission and available at and


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 i Pandemic Influenza. Centers for Disease Control and Prevention. Last reviewed June 14, 2023. Accessed on May 27, 2023.