Flu shots have been around since World War II, and the Centers for Disease Control and Prevention has long recommended shots as a way to prevent influenza in the elderly. The approval of a new nasal spray vaccine begs the question whether those looking to stave off the flu should stick with the tried and true injection or switch to the nasal spray.
"We really don't know whether one is superior to the other in adults," said Arnold Monto, professor of epidemiology at the U-M School of Public Health and a life-long researcher on cold and flu. "We want to be able to say whether there is an advantage in protection."
Both the injectable flu shot and the inhaled nasal spray use three different strains of flu every year as their base. A group of leading scientists uses disease surveillance to predict which types of flu are most likely to become a problem in the United States, and vaccines produced annually protect against those types.
The flu shot uses killed virus, meaning it is formulated using flu virus that's killed and injected into the patient to encourage a low-level immune response. Triggering this response helps the patient's body fight off later encounters with those strains of flu.
The nasal spray uses live but weakened cold-adapted virus. It is specially grown so that it can survive in the cooler conditions of the nose, but not in the warmer lungs, where flu takes hold.
Monto wants to understand the different ways humans respond to killed or live virus vaccines. For example, he already knows that people who get the nasal spray sometimes might develop fewer antibodies---the body's front-line warriors called up for duty in the presence of a threat---than people who get the shot, but they might still be protected.