[howlgarnish]

Dengue is odd in that surviving an attack of one strain makes you immune to that strain, but increases the odds of getting severe complications if you catch one of the other ones. Which is which dengue vaccine is only recommended for people who have already had it once!

[klipt]

One theory why that happens:

https://en.wikipedia.org/wiki/Antibody-dependent_enhancement

[hatsunearu]

Oh shit, this explains why my mom got severely sick on her second round.