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Our progress in developing a potential COVID-19 vaccine

In confronting this crisis, we believe that science will win.


In the fight against COVID-19, a vaccine is a critical part of addressing the global health crisis by decreasing rates of infection, disease and death worldwide.

Pfizer and BioNTech have been leveraging decades of scientific expertise and working together to develop, test and manufacture a mRNA vaccine to help prevent COVID-19. The Phase 2/3 clinical trial began in late July. On 9th November our CEO Albert Bourla shared our interim efficacy results highlighting the progress achieved to date and on 2nd December the Medicines & Healthcare Products Regulatory Agency (MHRA) in the U.K. granted a temporary authorisation for use of our COVID-19 mRNA vaccine.


Phase 2/3 Trial Update

Developing a potential breakthrough vaccine to help prevent COVID-19 is only possible through the dedicated work of thousands of individuals and those who volunteer to take part in research.

We are grateful to each of approximately 150 clinical trial investigators and their study teams who are partnering with us in this effort and to all 46,331 participants who have volunteered to help make a difference for society.


Pfizer has a deep heritage in vaccine development. Our team of in-house experts has decades of experience developing vaccines and study protocols (a document that outlines the objectives, design, and methodology for a clinical trial), to potentially help prevent serious, emerging, and life-threatening infections and diseases. 


What's Next?

In February 2021,  Pfizer began its Phase 2/3 global clinical trial to further evaluate the safety, tolerability, and immunogenicity of the BNT162b2 COVID-19 vaccine in preventing COVID-19 in healthy pregnant women 18 years of age and older. Pregnant women have an increased risk of complications and developing severe COVID-19, so it is critical that we investigate the potential safety and efficacy of a vaccine for this population.

The study will enrol 4,000 participants at more than 130 global sites, the first of which is in the US, with more expected to be added in the coming months. Each woman will participate in the study for approximately 7 to 10 months, depending on whether she was randomised to receive the vaccine or placebo. The study will also assess safety in infants of vaccinated pregnant women and the transfer of potentially protective antibodies to their infants, who will be monitored through to approximately six months of age.

Prior to conducting their COVID-19 vaccine clinical trial in pregnant women, Pfizer and BioNTech completed a developmental and reproductive toxicity (DART) study with BNT162b2, which was required by the regulatory authorities before starting the study in pregnant women. Those studies showed no evidence of fertility or reproductive toxicity in animals.

Pfizer is leveraging its expertise in conducting clinical trials in pregnant women, informed by the trials for other vaccine candidates. Safety will be closely monitored by the internal study team as well as an independent Data Monitoring Committee throughout the course of the trial.


The investigational vaccine

What kind of vaccine is the investigational vaccine?
The investigational vaccine is an mRNA vaccine. It is a kind of vaccine that gives a body's cells instructions to make viral proteins that can be recognised by the immune system. It contains a small part of the genetic code for the SARS-CoV-2 spike protein. By delivering the mRNA to the body’s cells, the viral protein is expressed and an immune system response is generated against it, with the goal of preventing COVID-19 disease. The vaccine does not contain any live virus.



Clinical Trial Design and Endpoints

Where are the Phase 2/3 clinical trials taking place?
There are approximately 150 clinical trials sites in six countries; the US, Germany, Brazil, Argentina, South Africa and Turkey. 


What is the objective of the Phase 3 clinical trial? 
The Phase 3 portion of the clinical trial is designed to determine if our candidate is effective in preventing COVID-19 disease and to generate robust safety data. This part of the trial began on 27th July and is estimated to enroll up to 44,000 participants. If successful, the next step will be to seek regulatory review and emergency use authorisation or approval.



What are the endpoints in your study?
The primary endpoints of our COVID-19 vaccine study are to evaluate the efficacy of the vaccine candidate in preventing COVID-19 disease in participants who have not been infected with the SARS-CoV-2 virus before they receive the vaccine, and to evaluate potential prevention of COVID-19 disease in participants who have had prior exposure to SARS-CoV-2. 

The primary efficacy endpoints evaluate confirmed COVID-19 cases occurring 7 days or more after the second dose. The final analysis also will include, with the approval of the FDA, secondary endpoints evaluating efficacy based on COVID-19 cases occurring 14 days after the second dose. Pfizer and BioNTech believe that the addition of these secondary endpoints will enable assessment of data across all COVID-19 vaccine studies and allow for cross-trial learnings and comparisons between various vaccine platforms. 

Pfizer also plans to continue to accumulate safety and long-term outcomes data from participants for a full two years. 


How are you able to move with this speed in the trial? 
Even though we are moving with extraordinary speed, preservation of high quality and safety standards is critically important throughout development. We are taking all of the regulatory and operational steps that we would normally take for all of our vaccine trials, maintaining the highest standards in our development process. This required enormous mobilization of Pfizer and BioNTech resources upfront at a scale never seen before. We are also working closely with regulatory agencies, providing near real time data and receiving review and advice more quickly than ever before, to support the development of this potential vaccine as quickly as possible. 

The UK government recently illustrated how the clinical trial process is being accelerated by running concurrent trials and large scale production - find out more.


How is the study designed and reviewed over time? 

The full study protocol is available to view on the EU Clinical Trials Register.

The study is designed to take place in multiple locations (multi-center), in different countries (multi-national), and participants have a 50% chance of receiving either the vaccine candidate or a placebo (randomized, placebo-controlled). 

The study is also “observer-blinded,” which means that trial participants and investigators do not see the vial that contains the vaccine candidate or placebo. This accounts for any visual differences that may exist between the vaccine candidate and placebo, and adds to the rigor of the study. 

Participants are given two doses of the vaccine candidate or placebo, 21 days apart. Participants will continue to be monitored for long-term protection and safety for an additional two years after the second dose. 

The study is a case count, or “event-driven,” study: investigators report the number of cases of COVID-19 disease that occur in those who receive the vaccine candidate and those who receive the placebo. If there are many more COVID-19 cases in the placebo group, as compared to the vaccine group, this is scientific evidence that our vaccine candidate is effective in preventing COVID-19 disease. 


Clinical Trial Participants

Why did you expand enrollment for the Phase 3 trial? 
In September 2020, Pfizer expanded the enrollment of its Phase 3 pivotal COVID-19 vaccine trial to approximately 44,000 participants. This allowed for the enrollment of new populations, including adolescents as young as 16 years of age and people with chronic, stable HIV (human immunodeficiency viruses), Hepatitis C, or Hepatitis B infection. In October 2020, we received permission from the FDA to enroll adolescents as young as 12. By doing so, we will be able to better understand the potential safety and efficacy of the vaccine in individuals from more ages and backgrounds. 


COVID-19 has disproportionately affected underrepresented populations. How are you addressing this in the trial? 
We are committed to decreasing health disparities in underrepresented populations through our clinical trials. We have selected investigative sites in diverse communities in the U.S. and globally that have been disproportionately affected by COVID-19, to help ensure that individuals in communities that have been most impacted have the opportunity to participate. We have shared with our investigative sites the importance of recruiting individuals who fully represent the racial and ethnic diversity of their communities, and we are engaging patient advocacy partners and community groups to raise awareness about the importance of participation and representation. 


Clinical Trial Integrity

What mechanisms are in place to ensure the integrity of the trial?
Before our trial began, the protocol was reviewed and approved by the U.S. Food and Drug Administration (FDA), regulatory authorities in the other countries where the trial is taking place and institutional review boards (IRBs) or ethics committees. 

Throughout the trial, progress is closely tracked by an external group of independent experts, called a Data Monitoring Committee (DMC), which also monitors our study for safety on an ongoing basis. 


What is an Institutional Review Board (IRB)?
An IRB is a group appropriately constituted under FDA regulations that has been formally designated to review and monitor biomedical research involving humans. An IRB has the authority to approve, require modifications in or disapprove research. This review serves an important role in the protection of the rights and welfare of research participants. 

The purpose of the IRB is to assure, both in advance and by periodic review, that appropriate steps are taken to protect the rights and welfare of people participating in the research. To accomplish this purpose, IRBs use a group process to review research protocols and related materials (e.g., informed consent documents and investigator brochures) to ensure protection of the rights and welfare of participants. 


What is the Data Monitoring Committee (DMC) and how is it structured?
The DMC for our COVID-19 vaccine trial currently consists of a chairperson and four additional members. The members are independent experts with extensive experience in paediatric or adult infectious diseases, vaccine safety and statistics. All DMC members have prior experience as members of DMCs. 


Commitment to Safety

How are you monitoring the safety of trial participants? 
Participant safety is paramount. As with all of our trials, we are following all of the rules and regulations in place to ensure participant safety. For example, the trial protocols are reviewed by regulatory authorities and approved by ethics committees or Institutional Review Boards, which are independent committees that review the methods proposed for research. In addition, the trial’s progress is closely monitored by both Pfizer and an outside group of independent experts called a Data Monitoring Committee or DMC. Trial investigators are also responsible for monitoring participants' health, and participants in the trial have regular planned follow-up visits as part of the trial. 


What is a “serious adverse event” and what will happen if a trial participant reports one?
A serious adverse event (SAE) in this trial, and in all standard clinical protocols, is any untoward medical occurrence that causes death, is life-threatening, requires hospitalization, or results in disability, whether or not it is considered related to the investigational vaccine. 

Serious Adverse Events Following Immunization (AEFI) in the clinical trial are analysed to understand if they could be causally related to the trial intervention, and follow-up actions are taken as appropriate. 

AEFIs are reported to regulatory agencies, as well as to an outside group of independent experts called the Data Monitoring Committee (DMC), which has access to unblinded data.  


Access to a Vaccine

When is the earliest the vaccine will be available to the public? 
We are in dialogue with regulatory agencies around the world, including the Medicines and Healthcare products Regulatory Agency (MHRA) in the UK and the European Medicines Agency, to ensure we provide the data necessary to assess our clinical programme in a timely manner. 


Who will get the vaccine first, if it is approved? 
We are working with governments around the world to provide and distribute our vaccine, if authorised or approved. Those governments and local regulatory authorities would provide the vaccine as they determine is appropriate. 

In the UK, the prioritisation of who receives the vaccine is led by the Joint Committee on Vaccination and Immunisation; more information can be found here.


Partnership with BioNTech

How does your partnership with BioNTech work?
Pfizer and BioNTech first announced plans to co-develop a potential COVID-19 vaccine in March 2020. The rapid advancement of the collaboration builds on the research and development collaboration into which Pfizer and BioNTech entered in 2018 to develop mRNA-based vaccines for prevention of influenza. 

The collaboration leverages BioNTech’s proprietary mRNA vaccine platforms and Pfizer’s broad expertise in vaccine research and development, regulatory capabilities, and global manufacturing and distribution network. 


PP-PFE-GBR-3487 / Feb 2021