A Universal Flu Vaccine Is in the Works, and Could Replace Your Annual Flu Shot

Each year, people around the world receive a new influenza vaccine—also known as your annual flu shot. Because the flu—one of the most wide-spread viruses—mutates so quickly, scientists must revamp the vaccine each year to account for new strains that arise.

Now, scientists are working to develop a universal flu vaccine that could protect the body against diverse influenza strains and subtypes for years, doing away with the annual flu shot. In a study published last week in the journal Nature Medicine, researchers announced promising results from a phase I clinical trial of the vaccine.

In this clinical trial, researchers from Mount Sinai studied the vaccine’s safety and ability to provoke an immune response to the vaccine. A study of 65 trial participants in the U.S. ages 18 to 39 indicated that the vaccine “induced a broad, strong, durable and functional immune response,” which endured for at least 18 months, according to the study’s authors.

The authors state that this vaccine could provide long-term protection after only two or three doses.

“In terms of a universal flu vaccine’s impact on public health in the United States, it could reduce flu-associated morbidity and mortality for both seasonal and pandemic influenza,” Vivien Dugan, PhD, MS, deputy director of the Centers for Disease Control and Prevention (CDC) Influenza Division, tells Verywell in an email.

How the Universal Vaccine Works

Each year, the influenza virus mutates and “reassorts” genes between strains. When it mutates, the body’s immune response may not recognize the new variation of the virus, causing some strains to avoid both natural and vaccine-induced immunity.

Scientists develop new vaccines every year to account for such mutations. The vaccine protects against the three to four strains they predict will be most common in the coming year. It typically contains a mix of weakened or inactivated viruses with a mix of hemagglutinins (HAs)—the proteins that cover the surface of the influenza virus.

The typical flu shot attempts to build an antibody response to the head of the HAs. There is a small part of the head that mutates frequently so that the antibodies are unable to recognize and defend against the virus.

This new vaccine incites antibodies to target the stalk of the surface protein, rather than the head. The stalk is much less prone to mutation and stays structurally the same in each variation of the influenza virus. However, the body’s immune responses are trained to respond strongly to the HA’s head, overriding antibody production for the stalk.

To get around this, the Mount Sinai team created what they call the chimeric HAs vaccine. These have the same stalks but unfamiliar heads, which trigger a much lower antibody response to the head and a higher response to the stalk.

“The beauty part of this vaccine is that it’s not only broad, but multifunctional with stalk-specific antibodies that can neutralize many kinds of influenza viruses,” Adolfo García-Sastre, PhD, co-author of the study and director of the Global Health and Emerging Pathogens Institute at the Icahn School of Medicine at Mount Sinai, said in a press statement.

With a chimeric HA-based vaccine, people may have long-term immunity to many variants of influenza after two to three shots, the authors say. This could be helpful for public health efforts to increase immunity across a population.

“This universal vaccine could be particularly beneficial to low- and middle-income countries that don’t have the resources or the logistics to vaccinate their populations each year against influenza,” García-Sastre said.

Implications of a Universal Vaccine

The typical influenza shot includes three to four strains of the virus which scientists think are most likely to circulate in the coming year. Through a global network of health centers, scientists gather data on which strains of the virus are most prevalent during the flu seasons in each region, in order to predict which strains will most likely circulate worldwide the following year. Because it can take six months to develop a flu shot, the strains included in the vaccine may not match those that are actually circulating when flu season starts.

A universal flu shot could provide effective protection against an array of influenza strains.

The ability to vaccinate many people with a universal flu shot could minimize the effect of a pandemic virus. As seen in the H1N1 outbreak in 2009, these viruses can emerge unexpectedly. When this happens, scientists need to generate new vaccines to match the pandemic strain—a process that can take six months.

“An influenza virus vaccine that results in broad immunity would likely protect against any emerging influenza virus subtype or strain and would significantly enhance our pandemic preparedness, avoiding future problems with influenza pandemics as we see them now with COVID-19,” Florian Krammer, PhD, professor of microbiology at the Icahn School of Medicine at Mount Sinai, and co-author of the study said in the statement.

Updating the Vaccine

The Mount Sinai study is one of several stalk-based universal flu vaccine candidates.

“Developing a universal flu vaccine poses an enormous scientific and programmatic challenge, but a number of government agencies and private companies already have begun work to advance development of a universal flu vaccine,” Dugan says.

Part of what makes the process so challenging, she says, is that each person who receives a vaccine is different. Different factors can come into play when determining the benefits someone might receive from the vaccine, including:

• A person’s age
• Underlying medical conditions
• History of prior infections
• Prior vaccinations

The U.S. Department of Health and Human Services is working toward the long-term goal of creating a universal flu shot in collaboration with the CDC and other agencies.

“Efforts, resources, and advanced technologies allocated to the rapid development of safe COVID-19 pandemic vaccines may be broadly applicable to future influenza vaccine development, including approaches towards a universal influenza vaccine,” Dugan says. “This is something that CDC, federal partners, industry, and other domestic and international public health partners are exploring.”