Flu Shot and Nasal Spray Flu Vaccine Tested Side by Side

A University of Michigan influenza expert is beginning a three-year direct comparison of the effectiveness of flu shots versus nasal spray flu vaccine.

Flu shots have been around since World War II, and the Centers for Disease Control and Prevention (CDC) 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.

What he doesn't understand yet is whether other substances developed in response to the nasal spray might somehow be more effective.

The study will enroll about 2,000 people at sites in Ann Arbor, Livonia and Mount Pleasant, Mich. They will receive a shot, nasal spray or a placebo.

Monto's team will monitor the participants to see who gets the flu, and compare the effectiveness of the two vaccines to each other as well as to the rates of disease in the unvaccinated group. Participants will give blood samples and scientists will look at antibody levels for the three groups.

FluMist, the nasal spray flu vaccine, is based on technology developed by Hunein "John" Maassab, professor emeritus of epidemiology at the U-M School of Public Health. U-M licensed the technology to MedImmune Inc., and receives royalty payments in addition to holding a small equity stake in the company.

The U.S. Food and Drug Administration is monitoring conduct of the study, which is supported by a $3.6 million, three-year grant from the National Institutes of Health.

The study will only include adults ages 18-46. FluMist is approved for adults ages 18-49; enrolling the first year at age 46 allows patients to finish the full three-year study and still be in the approved age group to receive FluMist.

According to the CDC, between five and 20 percent of U.S. residents will get influenza each year; an estimated 114,000 will be admitted to the hospital and 36,000 people will die as a result of influenza infection each year in the United States.

Monto's study aims to determine how the vaccines work to control annual influenza outbreaks and to gather valuable information for influenza pandemic planning. An influenza pandemic is a global outbreak of influenza, which occurs when a new influenza A virus emerges among people, spreads, and causes disease worldwide. Past influenza pandemics have resulted in widespread illness, increased mortality, social disruption and economic loss.

Source: University of Michigan