Immunologic response of unvaccinated workers exposed to anthrax, Belgium., Wattiau, P, Govaerts Marc, Frangoulidis Dimitrios, Fretin David, Kissling Esther, Van Hessche Mieke, China Bernard, Poncin Martine, Pirenne Yvo, and Hanquet Germaine , Emerg Infect Dis, 2009 Oct, Volume 15, Issue 10, p.1637-40, (2009)