mRNA Flu Shot Moves Forward As Pfizer Launches Late-Stage Trial, Builds On Covid Vaccine Success

Published 1 year ago
Injection of the third dose of the covid 19 vaccine at a Covid-19 vaccination center in Dinan, Brittany


Pfizer announced on Wednesday it has launched a late-stage clinical trial to test a flu vaccine built using the same mRNA technology behind its Covid-19 shot, one of the most advanced studies for this kind of vaccine as firms push to expand beyond Covid and build upon the successes of the pandemic.


Pfizer said it had dosed the first participants in the Phase 3 clinical trial designed to test an mRNA-based influenza vaccine designed using the same technology used in its widely-used Covid-19 vaccine, which it developed with German firm BioNTech.

The trial, which is based in the U.S., will assess the safety and effectiveness of the shot and will recruit around 25,000 healthy adults. 


The shot—known as a quadrivalent vaccine—is designed to protect against four different flu viruses and covers the strains the World Health Organization recommends vaccine makers target for the 2022-2023 flu season.

Annaliesa Anderson, senior vice president and chief scientific officer of Pfizer’s vaccine research and development, said the firm’s experience with mRNA vaccines give it an edge in the quest to develop more effective flu vaccines. 

Pfizer added that the nature of the mRNA technology in the vaccine could enable more flexible and responsive vaccine production for seasonal influenza in the future or against pandemic flu.


The flu is a major killer and a significant driver of ill health. Every year in the U.S., seasonal flu sickens an estimated 9 million to 41 million people, hospitalizes 140,000 to 710,000 and kills 12,000 to 52,000, according to the CDC. Influenza is also a pathogen of known and demonstrated pandemic potential—there were three influenza pandemics in the 20th century, one of which killed an estimated 50 million people—and experts caution the next flu pandemic is a matter of “when,” not “if.” Numerous influenza viruses can cause the disease and these mutate rapidly, meaning that pharma firms and public health officials must try to predict what strains will circulate that season and match vaccines accordingly. The guessing game varies and shots typically offer between 40% to 60% protection, according to the CDC, less if the vaccines are not well-matched to circulating strains. The need to constantly update flu vaccines on an annual basis and the long lead times to produce shots (the virus is usually grown in chicken eggs or mammalian cells) make the shots good candidates for a shot using mRNA technology, which introduce genetic material that prompts the body to make a safe part of the virus that it is then trained to respond to in the future. As only the genetic sequence is needed, the process is more flexible and can be easily edited. 



290,000 to 650,000. That’s about how many people worldwide are killed by the seasonal flu every year, according to the World Health Organization. It causes between 3 million and 5 million cases of severe illness. 


Moderna, Pfizer’s mRNA vaccine rival, is also trailing its own mRNA-based flu vaccine. It launched Phase 3 trials in June and is one of the company’s most advanced vaccine candidates beyond its Covid-19 shots. It is one of a number of flu shots the Massachusetts-based firm is developing, including shots that combine vaccines for flu, Covid and respiratory syncytial virus, or RSV, a respiratory illness that can cause serious illness in infants and older adults.


By Robert Hart, Forbes Staff