"To everyone's surprise and increasing consternation, this vaccine has performed quite poorly compared to the injectable vaccine," said Dr. William Schaffner, an infectious disease specialist.
An alternative to the standard flu shot, FluMist had been approved for people between the ages of 2 and 49 years old by the Food and Drug Administration.
The CDC committee, which includes 15 immunization experts, reviewed data from previous flu seasons, including the most recent season, comparing FluMist with the standard flu shot.
The decision must now be approved by the CDC director, Dr. Tom Frieden before taking effect.
The FDA first approved the nasal spray
in 2003. MedImmune, a subsidiary of London-based AstraZeneca PLC, produces FluMist, a live attenuated influenza vaccine. By contrast, the flu shot is an inactivated influenza vaccine.
Though the viruses in FluMist are live, they have been weakened (attenuated, in medical terms) and work by stimulating the immune system. There are two versions of FluMist: one a trivalent vaccine, which protects against three strains of flu virus, and the other a quadrivalent, protecting against four strains.
"We agree with [the Advisory Committee on Immunization Practices'] decision today to recommend health care providers and parents use only the inactivated vaccine," Dr. Benard Dreyer, president of the American Academy of Pediatrics, said in a statement. The Pediatric Infectious Disease Society also stated its support during the hearing.
Yet, prior to its recent poor performance, all evidence showed the spray worked better than the flu shot in children under the age of 8. And, during those sunny days, the CDC committee expressed a preference for the mist over the shot.
"That lasted exactly a year," explained Schaffner. Still, the nasal spray had become a favorite among pediatricians.
"Kids in general prefer the FluMist," Atlanta pediatrician Dr. Jennifer Shu said. "I'm the same way; I'm needle-phobic."
She said one drawback of the nasal spray is it may cause a runny nose for a day or two. "Half the time, these kids have a runny nose anyway, especially young children," she said.
An estimated one-third of all flu vaccinations administered to children are nasal spray, according to the CDC. Pediatricians are likely to be most impacted by Wednesday's recommendation, especially those who have already placed orders for vaccines in advance of the upcoming flu season. "CDC will be working with manufacturers throughout the summer to ensure there is enough vaccine supply to meet the demand," the agency said in a statement.
The FDA had been working with MedImmune to determine why the spray had begun to work so poorly.
Each February, an FDA committee makes the final decision about which virus strains will go into vaccines sold in America for the coming season. Its decision is based on information from more than 100 countries, where influenza-monitoring centers conduct surveillance of circulating viruses. The committee considers which viruses are making people sick, where those viruses are spreading and how well the previous season's vaccine protects against them.
After the committee selects the strains to be used for the vaccine, manufacturers
genetically adapt the strains to optimize the vaccine for the production process. Typically, trivalent formulations include two A strains and one B strain, while the quadrivalent formulations add a second B strain.
"So the question is whether there's something in the process that alters the strain," Schaffner said. Because the underlying science is so complex, there are no easy answer, he said.
Dr. Haihao Sun of the FDA's Office of Pediatric Therapeutics said the inconsistent effectiveness
results were a concern to the agency.
During the hearing, Dr. Chris Ambrose of MedImmune shared results from the company's 2015-16 influenza vaccine effectiveness study, which found the FluMist quadrivalent vaccine to be 46% effective, compared with the flu shot's 65% effectiveness. However, Dr. Brendan Flannery of the CDC presented data indicating that FluMist had zero effectiveness against one strain of flu.
Acknowledging that FluMist offered advantages in the past, especially for children, Sun said the FDA would continue to work with MedImmune. "At this point, we're not ready to take a requirement for changing prescribing information," he said.
Wednesday's recommendation is an interim decision that could be reversed when the panel reconsiders it next year with additional data.