Editor's Note: Don't miss our other reports on the Center for Disease Control and Prevention's (CDC's) influenza vaccine recommendations for 2016-2017, including CDC Provides Vaccine Recommendations for the 2016-2017 Influenza Season and Flu Vaccine for People With Egg Allergies. In addition, please visit our Influenza Resource Center often for updates.
In this commentary, I will discuss an important change in the US 2016-2017 influenza vaccine recommendations. Specifically, I will explain why we are recommending that only injectable influenza vaccines (inactivated influenza vaccine [IIV] or recombinant influenza vaccine [RIV]) should be used during the upcoming influenza season. The intranasal live attenuated influenza vaccine (LAIV), sold under the trade name FluMist® Quadrivalent, should not be used during the 2016-2017 flu season because of concerns about the effectiveness of that vaccine.
Before I discuss the data behind this decision, I would like to say that we realize that this change may cause substantial inconvenience for many vaccine providers, particularly those who care for pediatric patients. We also understand that the change may raise questions and concerns, especially among parents who have become accustomed to their children receiving the nasal spray flu vaccine. We hope that the information provided here will help you to better understand and explain why LAIV should not be used this season.
Let me provide some background on the development and evolution of our recommendations related to LAIV.
CDC's Advisory Committee on Immunization Practices (ACIP) is a panel of immunization experts who develop vaccine recommendations for children and adults in the United States. ACIP's recommendations become official CDC policy after being reviewed and approved by CDC's director. ACIP considers many factors before developing recommendations for vaccines, including vaccine effectiveness data. After vaccines are recommended and in use, scientists continue to monitor how well they are performing. New data are regularly shared with ACIP, and vaccine recommendations may evolve as a result to make the use of vaccines as beneficial to the public's health as possible.
In the case of LAIV, from 2003 (when the vaccine was first licensed and recommended) through the 2013-2014 season, ACIP and CDC expressed no preference for LAIV. Then, for the 2014-2015 season, ACIP and CDC issued a preferential recommendation for the use of LAIV for healthy children aged 2 through 8 years. This recommendation was based on data from two randomized controlled trials of LAIV and IIV among young children that showed superior efficacy of LAIV.[1,2] These studies were conducted before the 2009 pandemic, during the 2002-2003 and 2004-2005 influenza seasons, respectively.
However, in February 2015, ACIP and CDC did not renew their preferential recommendation for LAIV for children aged 2 through 8 years. The decision not to renew the preferential recommendation for LAIV was based on poor LAIV effectiveness against H1N1 influenza viruses during the 2013-2014 season and a lack of evidence that LAIV provided better protection than IIV against antigenically drifted H3N2 viruses during 2014-2015.
This brings us to the current season's recommendation. On June 22, 2016, ACIP was presented with new data on the effectiveness of flu vaccines among children aged 2 through 17 years during the 2015-2016 season when H1N1 viruses predominated. These data came from the US Influenza Vaccine Effectiveness Network and showed that the point estimate for LAIV vaccine effectiveness among children in the study against any flu virus was only 3% and not significant, with a 95% confidence interval of -49% to 37%. This finding essentially means that no protective benefit from LAIV could be measured, especially against H1N1 viruses.
In comparison, IIV offered substantial protection, with a significant vaccine effectiveness point estimate of 63% against any flu virus among children in the study. The 95% confidence interval ranged from 52% to 72%.
During the June meeting, ACIP also discussed additional non-CDC studies, which found, overall, that the LAIV did not work as well as the IIV. The vaccine effectiveness point estimate for H1N1 was lower for LAIV than IIV in all studies, and most of the LAIV vaccine effectiveness estimates against H1N1 were not statistically significant.
Given these data—and the fact that each year in the United States, millions of people are sickened, hundreds of thousands are hospitalized, and thousands or tens of thousands die from flu—ACIP recommended that only injectable influenza vaccines (either IIV or RIV) be given during the 2016-2017 season. The upcoming flu season's vaccine options are listed in the table of US influenza vaccines in the ACIP influenza vaccine recommendations for 2016-2017, published in Morbidity and Mortality Weekly Report, and are also discussed in a separate Medscape commentary, Vaccine Recommendations for the 2016-2017 Influenza Season.
Vaccine manufacturers have projected that as many as 157-168 million doses of injectable influenza vaccine will be made available for the 2016-2017 season. This number of doses is higher than has ever been used during a regular flu season in the United States. Based on these projections, the supply of injectable flu vaccine should be sufficient to meet an increase in demand resulting from the recommendation to not use LAIV this season. However, providers may need to check more than one supplier or purchase a different flu vaccine brand than usual. Information on flu vaccine available for purchase by providers can be found in the Influenza Availability Tracking System IVATS Report.
Flu vaccines are our first line of defense to protect against influenza infection, so it's disheartening to see data showing that LAIV did not perform as well as expected. Much of the data ACIP used to make its decision were gathered via the Seasonal Influenza Vaccine Effectiveness Network, which has been expanded in recent years to provide information to support policy decisions. While it is unfortunate to lose one of our vaccine options, the change in the ACIP recommendations is an example of using new data to hone public health practice to be most beneficial.
Fortunately, injectable influenza vaccines performed well last season and offered substantial protection against flu illness. With an overall vaccine effectiveness of nearly 50% among children and adults, injectable influenza vaccines protected millions of people against flu last season, preventing flu illnesses, doctor's visits, and hospitalizations. Flu vaccine is far from perfect, but it is the best way we have to prevent influenza. Please continue to strongly recommend flu shots for all of your patients aged 6 months and older. CDC will continue to monitor the effectiveness of influenza vaccines each year to help ACIP make informed decisions about their use.
Thank you for your attention and for all you do to protect the public against influenza. Contact CDC-INFO at 1-800-CDC-INFO or CDCINFO@cdc.gov if you have any questions following today's update.
Public Information from the CDC and Medscape
Cite this: No LAIV (Nasal Spray) Flu Vaccine This Season - Medscape - Sep 15, 2016.