Scientists working on three different types of flu shots say they are getting closer to a universal vaccine, having been thwarted by the virus's uncanny ability to mutate anew from season to season, and leaving even many vaccinated people vulnerable to the illness.
During the 2015–2016 season, only about half of those immunized were protected, according to a study in the Aug. 10 New England Journal of Medicine. Some years’ vaccines are duds: For the 2014–2015 season, the vaccine protected only 19 percent of people who received it, based on U.S. Centers for Disease Control and Prevention data.
Anatomy of the influenza virus:
Researchers often describe the flu virus as looking like a ball with lollipops sticking out. Tucked inside the ball is RNA, which the virus needs to make copies of itself. The lollipops on the outside are proteins: hemagglutinin and neuraminidase. There are 18 different kinds of hemagglutinin and 11 kinds of neuraminidase. Each kind of flu virus is named for its particular combination of these proteins; the current forms circulating around the world are H1N1 and H3N2. Hemagglutinin attaches to human cells to launch an infection; neuraminidase is more important for spreading the virus once infection has occurred.
Why immunizations change so often:
Like kids with a sweet tooth, the immune system gets most excited about the top part of the hemagglutinin lollipop, and makes antibodies against it. The top is, after all, the first thing the immune system notices once the virus slips inside the nose, mouth and lungs. Every year, genetic mutations in the virus slightly change the chemical flavor of the lollipop, making it more sweet or sour than last season’s — just different enough so the immune system doesn’t recognize it. That’s why most years there’s a new flu shot.
Three new approaches hold promise for discovering the perfect flu shot:
- Attacking the stem: Rather than formulating vaccines for the lollipop top response, scientists are hoping to obtain the same system-wide immune response by invoking antibodies against the stem.
- Pre-programmed T cells: Focusing on stable proteins within the virus, scientists have tried programming T cells to initiate an immune response when those proteins are encountered.
- Casting a wide net: Other scientists are attempting a one-size-fits-all approach by taking all known hemagglutinin mutations and packing them into one vaccine.