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IHEs have long required vaccinations of students—for human papillomavirus, meningococcus and influenza, for example.

More recently, reverse vaccinology led to a vaccine against meningococcus B6.

Many of the cases carry the same strain of meningococcus bacteria, known as serotype C, and have been linked through social connections, according to the health department.

The man who catches a meningococcus is in considerably less danger for his life, even without chemotherapy, than meningococci with the bad luck to catch a man.

Officials are unsure why the outbreak is disproportionately affecting gay men, but the cases are believed to be connected because patients were infected with the same strain of meningococcus bacteria, known as serotype C.