Jennifer Gefsky, Chappaqua resident and fitness instructor at Flywheel Sports in Scarsdale, will be serve as a co-host for Northern Westchester Hospital’s speaker series on adolescent health and the HPV vaccine on Thursday, Feb. 26. This discussion, part of the hospital’s ongoing speaker series, will focus on general health care for adolescents and answer questions regarding age-related issues for boys and girls. There will also be an overview of the human papillomavirus and the latest data regarding the HPV vaccine and answer questions about its impact on adolescent health.