Is there a long-lasting flu vaccine on the way?

Developing a long-term influenza vaccine could be extremely beneficial to public health, and research is moving closer to achieving this goal.

A study published in Science Translational Medicine found that creating a vaccine that additionally targets a region of the hemagglutinin (HA) glycoprotein that is less susceptible to mutations could be a way towards creating long-term influenza vaccination options.

The researchers tested their vaccine on mice and ferrets and found that it provided better protection than traditional vaccination. Although more research is needed, this successful test shows the direction for the future development of a long-term flu vaccine.

Problems in developing effective influenza vaccines

Influenza is a common infection that affects billions of people every year. The World Health Organization also estimates that influenza causes 3 to 5 million cases of severe illness and 290,000 to 650,000 respiratory deaths annually. Some people are more at risk for severe illness or complications from influenza, including children under five years of age and older adults.

Influenza viruses cause the flu, and these viruses change. The current strategy to protect against influenza is to use annual influenza vaccines. Experts create these vaccines based on which flu viruses they think will be most common during the flu season.

Changes in influenza viruses, especially in surface proteins such as hemagglutinin (HA), pose one of the challenges to creating a long-term vaccine.

Doctor Yoshua Quinonez, a board-certified internist at Manhattan Medical Offices, noted the following:

“Challenges with flu vaccines include the need to update them every year because the virus changes, certain parts of the virus that make the vaccine less effective, and the inability to protect against all types of influenza virus. It is also difficult to ensure that everyone can get the vaccine. But getting a flu shot can help reduce the number of people who get sick, protect those who can't get a shot, and perhaps one day have a vaccine that is effective against all types of flu. Boosting your immune system's response to the flu shot may also help protect against more types of influenza virus."

Is it possible to create a long-term universal vaccine against influenza?

Researchers in the current study note that annual flu vaccines help create antibodies that target specific areas of the HA head. However, this region is often subject to frequent mutations.

So if they could find a way to target an area of the HA that changes less, such as the stem, they could create a vaccine that could protect against many strains of influenza. However, although this has been tried before, it has not been effective in producing a strong response in the glans region.

So the researchers wanted to create a vaccine that could produce antibodies targeting the head and stem to offer long-term immunity against multiple flu strains. They ultimately created a vaccine based on the HA antigen mixture. This vaccine contained a mixture of HA proteins with a conserved stem and various mutations in the key head region.

The researchers in this study tested the vaccine's effectiveness in mice and ferrets. They compared the response to traditional vaccine approaches.

They found that their vaccine elicited a better antibody response than a control vaccine. The vaccine even provided protection when mice were exposed to lethal doses of the virus. It also offered protection against multiple strains of the H1 virus.

However, this newly developed vaccine was most effective after receiving an initial dose and a booster dose, rather than a single dose.

Medical director Linda Yancey, an infectious disease specialist at Memorial Hermann Health System in Houston, commented on the study results:

“This is a significant step toward a universal flu vaccine. Developing such a vaccine has been a goal of researchers for many years. It has proven challenging, so it is encouraging to see solid progress being made in this direction. At this time, scientists are still working to develop the building blocks of the vaccine. We likely will not see changes in clinical practice based on this for several years. But every step in the right direction gets us closer to a universal vaccine.”

Study Limitations and Continued Research

This study has limitations, primarily because animal testing is different from human testing. The animals also had no previous flu vaccinations or exposure to influenza, which could have affected the observed results. The researchers note that most people have some level of prior immunity to influenza, which could minimize or influence the response to this type of vaccine. The study also only looked at one H1 HA, so it is unclear how the approach would affect other HAs. Additionally, not all animal experiments were blinded.

The researchers also acknowledge that further study is needed to better understand the underlying mechanisms and confirm the reasons for the observed response. They acknowledge that “protection from infection may not always correlate with a reduction in classical antigen responses.”

Even if this potential vaccine is developed, experts, government agencies, and medical professionals will need to address issues of distribution and acceptance. Dr. David Cutler, a board-certified family physician at St. John’s Medical Center in Santa Monica, California, noted the following:

“While safety and effectiveness are the main concerns, vaccine acceptance is also an important issue. Currently, only about 50% of adults receive the flu vaccine. Any improvement in effectiveness could be offset by reluctance to receive the new vaccine. It is the job of our public health agencies to convince people that the benefits of approved vaccines far outweigh their risks. So, while scientists can develop new, improved vaccines, the benefits to society may not be realized if the vaccines are not administered.”

However, the study does raise the potential for developing a long-term flu vaccine. This could make it easier to maximize the vaccine’s impact and ultimately minimize the harmful health effects of influenza.

Kinonez expressed hope for the results, noting the following:

“The new flu vaccine may work better than the older ones. If it works in people as well as it does in animals, that could mean fewer people get the flu each year. It could also lead to a vaccine that would be effective against all types of flu, which would be a huge step forward in keeping people healthy."