Changes in small airway function after live attenuated influenza vaccination

Live, attenuated influenza vaccine was given by intranasal inoculation to 15 young, adult volunteers. Modest symptoms occurred within 3 days of challenge, but the agent was otherwise well tolerated. Hemagglutinin-inhibition antibodies increased in 9 of the 12 subjects whose initial volumes, but closing volume did not change. These changes in airflow reverted to previous levels after 1 week. On a second challenge 2 weeks after the first, symptoms were far less frequent, and no changes in airflow were detected. We conclude that this agent is biologically active and that the airflow changes observed may reflex involvement of small airways.