Some pediatricians and their patients were taken aback by the decision to drop the live attenuated influenza vaccine (LAIV) nasal spray as a recommended flu vaccine for the 2016-2017 season in the U.S.
Citing declining efficacy that essentially bottomed out last flu season, the CDC did not recommend LAIV this year, though it will still be available in Canada.
“I was really disappointed in their recommendation,” says Scott Field, MD, a pediatrician and flu researcher at the University of Alabama School of Medicine in Tuscaloosa. “In our experience, we had the lightest flu season I’ve ever seen this past year. So I couldn’t say whether any of the vaccines did not work well. I was very surprised that they came out saying don’t use the flu mist [vaccine].”
Field has had success with the LAIV vaccine in the past, and fears some of his patients may be less willing to be immunized now that the needleless spray option is gone. The change could translate to vaccination avoidance in needle-sensitive children who were immunized with the nasal spray.
“I’m really concerned about that,” he says. “We had a child who got the shot because he had asthma. His siblings got the [LAIV]. He was the only one in the family who got the flu. We finally got around to doing the [LAIV] on him, and ever since we did that he has not had flu. So the mom’s real upset this year that we are not going to have the mist.”
In making the decision, the CDC and its Advisory Committee on Immunization Practices (ACIP) conceded that in previous years LAIV was as effective or more effective than the seasonal flu shots. However, for reasons that are not completely clear, the LAIV showed lower effectiveness from 2013 through 2016. In addition, for the 2015-2016 season, LAIV effectiveness among children 2 years through 17 years was only an estimated 3% — meaning that no protective benefit could be measured, according to the CDC.
Of course, effectiveness of any flu vaccine may vary from year to year due to the vagaries of antigenic “drift” and the more dramatic “shift” of circulating influenza virus. Still, as recently as the 2014-2015 season, the CDC recommended the nasal spray vaccine over the flu shot for young children. During the 2015-2016 season, no preference was cited for either the LAIV or regular flu shots.
Canada Disagrees
LAIV contains live, weakened influenza viruses, which in theory should prompt a stronger immune response than the standard inactivated virus in flu shots.
“We don’t know why, but the vaccine efficacy data for the last couple of years suggest that it was not protective, and therefore we’re not recommending it,” CDC Director Tom Frieden, MD, noted at a recent flu vaccine press conference at the National Foundation for Infectious Diseases in Washington, DC. “It’s a really important vaccine. We know there are lots of kids who would much rather have the nasal spray than a shot. It’s a surprising finding, and we really do hope that we can get an effective intranasal vaccine or nasal spray back on the market and recommended as soon as possible.”
LAIV was initially licensed in 2003 as a trivalent flu vaccine and was expected to be taken this season in the U.S. by about 20 million people — primarily about one-third of vaccinated children.
Asked about the decision by Canadian health officials to continue to recommend LAIV this season, Frieden said, “Each country has to make its own recommendation. In the U. S. we have a very open, transparent process through ACIP, [which] looked at data from the U.S. and elsewhere of vaccine efficacy, and we found that there was no convincing evidence of efficacy. In contrast, the flu shots did have evidence of efficacy. So we feel that our responsibility in public health is to provide full information and to make recommendations based on information that’s openly and objectively derived.”
As it became apparent that LAIV would not be recommended, the CDC reached out to other manufacturers, who increased their production and distribution, Frieden says.
