In the wake of a continuing Hib vaccine shortage, caused by a recall of certain lots of the vaccine, authorities have urged alertness for suspected cases of invasive Haemophilus influenzae type B (Hib). The Hib bacterium is the most common cause of bacterial meningitis in children. The CDC said, in its Nov.21 Morbidity and Mortality Weekly report, to expect the shortage to continue till the middle of 2009.