As I'm sure we've all heard by now, the meningitis B vaccine has been on campus for about a week. Something that I've been curious about is why exactly the vaccine that was previously available is ineffective and why meningitis B is so difficult to properly vaccinate against.
The CDC has a lot of really great information regarding the different flavors of meningitis. Essentially, meningitis is caused by a bacterium called Neisseria meningitidis and there are 13 different serogroups and currently there are vaccines available for most of the major disease-causing ones (A, C, Y, and W135). Serogroup B, however, is a little different and the outer polysaccharide coating of the bacteria is poorly immunogenic, meaning that the immune system doesn't really have a response to it (kind of scary) which is why a vaccine has been so difficult to develop. And obviously since it's a different strain, previous vaccines wouldn't work so well.
The beautiful folks providing us with the vaccine also have some information about meningitis B (I'd take some of what they say with a grain of salt though).