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“Influenza is the most commonly occurring vaccine-preventable disease, resulting in an estimated 226,000 hospitalizations and 3000–49,000 deaths in the U.S. annually [1]. Influenza-related morbidity and mortality occurs primarily among the very young and very old, yet all age groups are affected, including young adults. Adults infected with influenza may become debilitated, bed-ridden, miss up to 6 days of work per infection, and require up to 2 weeks for full recovery

[2]. Accordingly, in 2010, the U.S. Advisory Committee on Immunization Practices recommended that all individuals ≥6 months of age be vaccinated against influenza annually, including adults 18–49 years of age without high-risk medical conditions [1]. In the U.S.,

intranasal live attenuated influenza vaccine (LAIV) PAK inhibitor and injectable trivalent inactivated influenza vaccine (TIV) are approved for use in eligible individuals. The Ann Arbor strain LAIV (MedImmune, LLC, Gaithersburg, http://www.selleckchem.com/PI3K.html MD, USA) was licensed in 2003 for use in eligible individuals 5–49 years of age. Initially, LAIV was not approved for use in children younger than 5 years of age because of an increased risk of asthma and wheezing noted in 1 study [3]; subsequent analyses showed an increase in medically attended wheezing in LAIV-vaccinated children aged <24 months, but not in children ≥24 months of age [4] and [5]. In 2007, LAIV was approved for use in eligible children ≥24 months of age. Outside of the U.S., LAIV is currently approved in South Korea, Israel, Hong Kong, Macau, Brazil, and the United Arab Emirates for eligible children and adults 2–49 years of age, in Canada for eligible children and adults 2–59 years of age, and in the European Union for eligible children 2–17 years of age. Since the initial approval of LAIV through the 2011–2012 season, more than 50 million doses have been distributed in the U.S.

LAIV use in adults has occurred primarily among U.S. military personnel, who have preferentially used LAIV in specific populations since 2004 [6] and [7]. During prelicensure clinical trials, the safety of LAIV was evaluated in 6140 Tolmetin adults 18 years of age and older [8], [9] and [10], and postlicensure randomized studies have evaluated the safety of LAIV in 2100 adults 18–49 years of age [11], [12] and [13]. The most common side effects of LAIV in adults include runny nose, headache and sore throat [14]. Previous studies of LAIV in adults have demonstrated comparable safety with TIV; most adverse reactions from either vaccine are mild, transient, and of minimal clinical significance [8], [11], [12] and [13]. In multiple-year studies, significantly fewer reactions occurred with revaccination [15]. At the time of the initial approval of LAIV in the U.S., MedImmune committed to the U.S.