Vaccines save millions of lives each year and protect against the development of, and natural infection with, harmful diseases, such as chickenpox, meningococcus, pneumococcus, and measles, mumps, and rubella (MMR). However, while anti-vaccine folks insist that vaccines cause neurological diseases, like meningitis and encephalitis, the truth of the matter is that the benefit of vaccination in preventing such diseases greatly outweighs the very minimal risk of vaccine complications.
While the varicella (“chickenpox”) and MMR vaccines in routine use in the United States can very rarely cause viral meningitis and measles inclusion body encephalitis (MIBE), respectively, natural infections can and do cause encephalitis and meningitis. Thus, the vaccines for MMR and chickenpox protect against encephalitis and meningitis caused by natural agents. The vaccines are made from attenuated versions of the natural/wild-type viruses, and generally do not cause central nervous system infections in normal hosts. Persons with certain immune deficiencies, however, can suffer from certain neurological diseases as a result of the attenuated vaccine viruses, and is therefore contraindicated in those populations.
Likewise, natural infections with meningococcus or pneumococcus can cause severe bacterial meningitis, but the vaccines that protect against them do not. The vaccines are made from only the outer capsule and/or bacterial proteins, meaning they cannot cause infections like the naturally occurring bacteria.
In sum, the fact that vaccines can, albeit very rarely, cause encephalitis or meningitis should not lead anyone to think that delaying and/or skipping a vaccine is a good idea. The chances of developing these neurological diseases are only increased by such actions.