Association of vaccine handling conditions with effectiveness of live attenuated influenza vaccine against H1N1pdm09 viruses in the United States.

•In 2013–2014, LAIV was effective against influenza B but not A/H1N1pdm09 in the US.•Lot shipping date and outdoor temperature were associated with VE against A/H1N1.•New analyses showed no significant LAIV VE against H1N1pdm09 in 2010–2011 in the US.•From 2010 to 2014, moderate to high VE for LAIV was observed against A/H3N2 and B.•A more heat-stable A/H1N1pdm09 LAIV strain was manufactured for 2015–2016.