Trend of bacterial meningitis in Bahrain from 1990 to 2013 and effect of introduction of new vaccines. 
Meningitis is among the 10 commonest infectious causes of death worldwide.  This retrospective analysis of reported cases of meningitis in Bahrain aimed to assess the trend in the incidence of bacterial meningitis from 1990 to 2013, before and after the introduction of new vaccines.  Of 1455 reported cases of meningitis during the study period 73.1% were viral and 26.9% were bacterial etiology (tuberculous meningitis 8.3%; Streptococcus pneumoniae 4.9%, Haemophilus influenzae 3.6% and Neisseria meningitidis 1.7%).  There was a peak of meningitis cases in 1995-1996.  The incidence of meningitis due to H. influenzae and N. meningitidis showed a marked reduction after the introduction of the corresponding vaccines in 1998 and 2001 respectively, and S. pneumoniae became the predominant organism after Mycobacterium tuberculosis.  The changing trend in the etiology of bacterial meningitis points to the need to study vaccination programme modifications, such as pneumococcal vaccine for the adult population, especially high-risk groups.