Jan. 18, 2019 -- With flu season in full swing, many people are counting on the protection of the flu shot they received earlier this season. Year in and year out, those who hope to avoid the nasty virus get the latest formulation of flu vaccine at drugstores and doctors’ offices around the country. But why do you have to get a new shot every year when vaccines against other illnesses protect you for years or a lifetime?
That’s the aim of a universal flu vaccine. Researchers have been trying to develop one for years. But unlike a disease like measles, for example, the flu is a moving target because its genetic makeup is a little different every season. That’s why you need a new formulation of the flu shot every year.
“The parts of the virus that the immune system generally targets are constantly changing,” says Tamar Ben-Yedidia, PhD, chief scientific officer at BiondVax Pharmaceuticals Ltd. “It’s hard to teach the immune system how to recognize a changing structure.” The company is one of several that have developed a universal flu vaccine being tested in clinical trials.
Flu shots work by teaching the immune system to recognize the invader so that it develops antibodies to fight it. In order to develop a universal flu vaccine, researchers had to identify a part of the virus that is unlikely to change from one strain to the next. They had to create a formula that will cause an immune response against that part of the virus.
“It wasn’t until the last 10 or so years ago that we were able to specifically identify those parts of the virus that don’t change,” says Anthony Fauci, MD, director of the National Institute of Allergy and Infectious Diseases at the National Institutes of Health. “Now there are multiple vaccine candidates in various degrees of clinical trials. The field is moving nicely in the right direction.”
The numerous candidate vaccines target different unchanging parts of the flu virus. One potential target is hemagglutinin, a protein found on flu viruses. “This protein attaches to the surface of cells and initiates the infection in your body,” says Rafi Ahmed, PhD, director of Emory Vaccine Center at the Emory School of Medicine in Atlanta.
Hemagglutinin looks like mushrooms covering the outside of the flu virus, with its round head and stem. Ahmed says that the stalk is consistent across different flu strains. Some universal vaccine candidates aim to immunize against this stem.
Other universal vaccine contenders target multiple unchanging parts of the virus all in one shot. The idea is to prepare the immune system for any surprises that a new flu strain might bring. That’s the aim of the BiondVax shot, now in phase III clinical trials, the furthest along of the numerous candidates. It’s being tested in people to see how well it works.
A couple of other drug companies, including UK-based biotech hVIVO, have completed phase II clinical trials and may be following close behind BiondVax.
BiondVax’s M-001 vaccine includes nine parts of the virus that don’t change. These viral parts contain segments common to 40,000 known flu strains, Ben-Yedidia says.
In previous clinical trials, M-001 was proven safe and triggered the immune system response expected of an effective vaccine. In the current phase III test happening in Europe, 4,000 volunteers ages 50 and over have received either M-001 or a placebo. Now, researchers and volunteers must wait.
In order for the shot to prove its worth, researchers have to see a big difference in the number of people who get the flu in the vaccine group and the placebo group. Results are expected in the second half of 2020. The shot must not only protect against any new flu strain that comes its way, but the protection also has to last for over a year.
“We’ll see,” Fauci says. “It could be that you need it maybe once every 3 years or maybe once every 10 years.”
Even with these approaches in the pipeline, it’s still anybody’s guess as to what form a universal flu shot will take and when you’ll get one at your local drugstore. BiondVax’s Ben-Yedidia is optimistic. “We are hopeful that [our] universal flu vaccine candidate will provide longer and broader protection so that people can be better protected from the ongoing threat of influenza -- the sooner the better.”