@article{Keitel1997,
author = {Keitel, W.A. and Cate, T.R. and Couch, R.B. and Huggins, L.L. and Hesst, K.R.},
title= {Efficacy of repeated annual immunization with inactivated influenza virus vaccines over a five year period},
year = {1997},
doi = {10.1016/S0264-410X(97)00003-0},
journal = {Vaccine},
volume = {15},
number = {10},
pages = {1114--1122},
}