Despite the availability of vaccines, millions of people still get sick from flu every year. Learn more about Pfizer’s research to help improve flu vaccines using mRNA technology.

We are exploring the potential of mRNA technology for use in flu vaccines. mRNA-based vaccines can be made faster than traditional flu vaccines which could make it easier to produce vaccines better matched to each season’s most common flu strains.

The availability of mRNA-based flu vaccines that are well matched to the current flu stains could potentially reduce the number of severe cases, hospitalizations, and deaths from flu each year. But we can’t advance the development of these vaccines without the help of clinical trial participants.

We invite you to join us in the fight against flu. By participating in clinical research, you're helping to make the next breakthrough possible — for yourself and others.

Not the right study for you? Click here to join PfizerLink, Pfizer’s research registry.

Who may participate

Joining a clinical trial is an important and personal decision. We thank you for considering participation.

This study is enrolling adults at least 65 years old who have not been diagnosed with flu and have not received a flu vaccine in the last 6 months. You may be eligible to enroll if you received a flu vaccine in the last flu season more than 6 months ago.

There are other requirements for taking part in this study. The study team will explain these to you if you’d like to learn more.

To see if you may qualify to participate, click “Get started”.


Flu (influenza


65+ years

Medical and vaccination history

Have not received a flu vaccine or tested positive for flu in the last 6 months

Each clinical trial has its own guidelines for who can participate, called eligibility criteria. However, only the research study staff can determine if you qualify to enroll in the study.

Get started — See if you may be eligible

Answer a 5-minute questionnaire.

A first step as you consider this study is to answer a 5-minute online questionnaire about your health and medical history. If your answers show the study might be a good fit for you, you may choose to be referred to a study clinic that you select.

Speak with a study representative.

If you’re interested, you will then be asked to provide your contact information for a study representative to contact you and discuss the next steps.

Confirm your eligibility.

Your answers to these questions will only be linked to you if your responses indicate that you may be eligible to participate in this study and you choose to share your contact information with the study team. Pfizer study team members and our partners will have access to reports containing aggregated data that will not be directly linked back to you. Only the study staff can determine if you meet the study’s eligibility criteria and are able to enroll in the study.

What to expect

The goal of this study is to understand if the investigational flu vaccine is safe and how the body’s immune system responds to the vaccine.

If you participate, your health will be monitored by the study team throughout the study. You will have two or three follow-up visits at the study site to see how you’re doing after receiving your study vaccination.

There is no cost to participate in this study, and health insurance is not required. You will also be compensated for completing study-related activities.

Length of study

About 6 months

Number of study visits

At least 3 to 4 visits

Understanding flu

Influenza or “flu” is a major cause of seasonal illness and death worldwide. It causes approximately 3 to 5 million cases of severe illness and up to 650,000 deaths worldwide every year.1

Influenza A and influenza B are the two main types of flu viruses that make people sick. There are many different strains of influenza A and B, and new strains are always evolving.

Flu is considered a seasonal illness because most cases occur during the fall and winter seasons. Since flu strains can change from one season to the next, flu vaccines are updated each year to closely match the flu strains that are circulating. Getting your annual flu shot is an important way to protect yourself and others from serious illness.

Understanding flu

Senior patient and healthcare provider reviewing information on a tablet together – Pfizer Clinical Trials
Senior patient and healthcare provider reviewing information on a tablet together – Pfizer Clinical Trials

Together, we can win the fight against flu

Immunization Infographic – Pfizer Clinical Trials
Immunization Infographic – Pfizer Clinical Trials
Source: What is Immunization Flyer,

Together, we can win the fight against flu

Participation by people of all backgrounds is critical to developing vaccines that protect against infectious diseases like flu. The greater the diversity among clinical trial participants, the more we can learn about potential vaccines and how they work for different people, including those most at-risk because of their age, race, ethnicity, or where they live. Each new vaccine breakthrough helps us reach more people to prevent and reduce the spread of disease.

Frequently asked questions

Which type of vaccines could I receive? 
The vaccines being studied are investigational mRNA-based vaccines designed to potentially improve the immune response against influenza A and influenza B. The study vaccines will be compared against licensed flu vaccines for the most recent (2023-2024) flu season.
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If I participate, will I need another flu shot before the next flu season?
If you have questions about subsequent flu shots, please discuss with your study doctor. If you do enroll in this study, you should wait to get your next annual flu vaccine until after you have completed your participation.
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What are the possible side effects? 
As with any vaccine, local reactions at the injection site can be common – such as redness, swelling, or pain. There is also potential for other symptoms like a mild fever or fatigue. The known side effects will be further explained in the informed consent document and discussed with you by the study doctor before you join the study. If there is any new information that we learn about the study vaccine during the clinical trial, the study doctor will share that with you as well. 
Is this helpful?
What kinds of tests and procedures are you going to perform? 
At the beginning of the clinical trial, the study doctor will ask you about your medical history, and any medications you are taking. You will be given an electronic diary to complete for one week after your vaccination so the study team can monitor your health. You will also have your blood drawn at least 3 times over the course of the study. The study team will give you more information about the tests and procedures during the review of the study’s informed consent document. 
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Learn more

1. Influenza (Seasonal). World Health Organization. Updated October 3, 2023. Accessed April 4, 2024.
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