Three years of poor performance of the live nasal spray influenza vaccine (LAIV) have resulted in an unusual policy shift from the US Advisory Committee on Immunization Practices. At their annual meeting yesterday to discuss influenza vaccination recommendations, the ACIP voted that the LAIV should not be used in the 2016-2017 influenza season. Data released in May 2016 showed that the LAIV effectiveness was effectively zero as compared with about 60% for the inactivated vaccine, given via injection.
According to the CDC, vaccine effectiveness is “the percent reduction in the frequency of influenza illness among vaccinated people compared to people not vaccinated.” No vaccine effectiveness was observed for the LAIV in children in 2013-14 nor in 2014-15. Based on these findings, last year the ACIP voted not to preferentially recommend the LAIV for young children over the inactivated vaccine. (The previous recommendations encouraged use of LAIV in children due to its assumed better performance at preventing disease.)
The new findings bring up many questions. When I asked vaccinologist Stanley A. Plotkin to comment on ACIP’s decision, he said, “The biological and immunological reasons for the recent failure of LAIV are unknown. As the vaccine previously appeared highly effective, it is important to determine what has changed.” Further investigations will attempt to identify why LAIV has failed to offer the protection expected.
This news undoubtedly will affect vaccine supply for the upcoming season. Though LAIV generally makes up about 8% of the entire influenza vaccine supply in the United States, it makes up about a third of influenza vaccine given to children. Apart from its previously presumed superior effectiveness, LAIV is preferred by many patients and parents who want to avoid injections
I asked infectious diseases physician and History of Vaccine advisor Thomas Fekete, MD, about his thoughts on this news. He said, “Many of our prior beliefs about this vaccine have been called into question. A Cochrane report suggested no benefit to vaccinating staff of nursing homes and that was our strongest argument for healthcare worker vaccination. The annual vaccine seems less effective when given annually, which may be an artifact of relative stability in the recommended strains covered. And now we have this indictment of the easier-to-tolerate inhaled vaccine. My personal belief is that we cannot vaccinate our way out of the flu problem with the current vaccines no matter whether they are dead, attenuated, or grown in baculovirus or eggs.” All the same, he said, “I still get the shot every year.” Indeed, the CDC continues to recommend yearly influenza vaccination for individuals age 6 months and older—just not with the LAIV. As Plotkin says, “Fortunately children can be protected from influenza by the injectable vaccine while additional studies are done.”