While it feels like summer just started, the Centers for Disease Control has already begun preparation for the next flu season. The CDC’s Advisory Committee on Immunization Practices (ACIP) voted that live attenuate influenza vaccine (LAIV) also known as the “nasal spray” flu vaccine, should not be used during the 2016-2017 flu season. ACIP is a panel of immunization experts that advise the CDC. Their decision to vote against using LAIV is based on data showing poor or relatively lower effectiveness from 2013 to 2016.
In late May, preliminary data on the effectiveness of LAIVE among children ages 2 through 17 in the last flu season (2015-2016) showed that LAIV vaccine effectiveness against any flu virus was 3%. This estimate shows that no protective benefit could be measured. However, the inactivated influenza vaccine (flu shot) and an effectiveness estimate of 63% against any flu virus in children ages 2 through 17. Data from the two previous seasons (2013-2014 and 2014-2015) also shows poor or lower than expected vaccine effectiveness for the LAIV.
How well the flu vaccine works (or its ability to prevent flu illness) can range widely from season to season and can be affected by a number of factors, including characteristics of the person being vaccinated, the similarity between vaccine viruses and circulating viruses, and even which vaccine is used. LAIV contains live, weakened influenza viruses. Vaccines containing live viruses can cause a stronger immune response than vaccines with inactivated virus. LAIV VE data before and soon after licensure suggested it was either comparable to, or better than, IIV. The reason for the recent poor performance of LAIV is not known.
The ACIP recommendation must be reviewed and approved by CDC’s director before it becomes CDC policy. The final annual recommendations on the prevention and control of influenza with vaccines will be published in a CDC Morbidity and Mortality Weekly Report (MMWR), Recommendations and Reports in late summer or early fall.
CDC has recommended an annual influenza vaccination for everyone ages 6 months and older since February 24, 2010. CDC and ACIP briefly had a preferential recommendation for nasal spray vaccine for young children (during 2014-2015); however, during the 2015-2016 season, influenza vaccination was recommended without any preference for one vaccine type or formulation over another.