Live attenuated influenza vaccine “shelved” for poor efficacy

Citing poor efficacy, the Centers for Disease Control and Prevention (CDC) Advisory Committee on Immunization Practices (ACIP) recently voted down the use of the live attenuated influenza vaccine (LAIV) for the 2016-2017 flu season. However, the committee further recommended annual flu vaccinations using either the inactivated influenza vaccine (IIV) or recombinant influenza vaccine (RIV) for everyone aged 6 months and older.

Having been approved by the US Food and Drug Administration (FDA) for persons aged between 2 and 49 years, the LAIV, also known as the “nasal spray” flu vaccine, was introduced into the market over a decade ago as an alternative to the injectable influenza vaccines such as the IIV and RIV options. The LAIV, on account of its painless mode of delivery, is clearly a preferred route of vaccine administration and was promoted and touted as a viable influenza vaccination option to the IIV and RIV. However, the recently available interim data demonstrating poor or relatively lower efficacy of the LAIV from the 2013 through 2016 flu seasons has led to the ACIP’s dissuasion to implement the nasal spray vaccine in patients.

“We agree with the ACIP’s decision to recommend healthcare providers and parents use only the inactivated vaccine for this influenza season,” says Benard P Dreyer, MD, professor of Pediatrics, director of Developmental-Behavioral Pediatrics, New York University School of Medicine, director of Pediatrics, Bellevue Hospital Center, and president of the American Academy of Pediatrics (AAP), New York.

The ACIP recently reviewed the preliminary data from the US Influenza Vaccine Effectiveness Network concerning the LAIV’s efficacy among children aged between 2 and 17 years during the 2015-2016 flu season and found that the nasal spray vaccine could provide only 3% protection against any flu virus in that patient cohort, a dismal record by any standard. In stark contrast, however, data also showed that the IIV flu vaccination option demonstrated a 63% protection against any virus in the same cohort.

This poor performance of LAIV protection during the 2015-2016 flu season was preceded by poor and/or lower-than-expected LAIV efficacy during the 2013-2014 and 2014-2015 flu seasons. The consecutively poor performances of the LAIV during the last few flu seasons has befuddled researchers, as the efficacy data of the LAIV before and soon after the FDA approval and licensure suggested it to be either comparable to, or better than, the IIV option.

It remains unclear as to why the LAIV fared so poorly in the last few flu seasons, and experts are still trying to figure this out. Current theories for the LAIV’s poor efficacy revolve around the strain in the vaccine being less effective when administered through the nose, or perhaps a change in the population that makes some persons more resistant to responding to the vaccine.

According to Dreyer, the news with the LAIV may be somewhat of a setback for those needle-phobic individuals who prefer to receive the flu vaccination painlessly via nasal spray. Fortunately, however, the IIV and RIV options appear to be working well. The AAP strongly recommends parents to annually immunize all children aged older than 6 months and, apparently, the superior flu vaccination options currently appear to be the IIV and RIV alternatives.

“It is absolutely paramount that people receive their annual flu shot, as the flu virus is an unpredictable and dangerous virus. The flu vaccine is the best way to protect children from the flu virus and, at present, it appears that the IIV and RIV injection vaccines are the most effective options currently available to achieve that goal,” Dreyer says.

Dr Petrou is a freelance medical writer based in Budapest, Hungary. He has nothing to disclose in regard to affiliations with or financial interests in any organizations that may have an interest in any part of this article.