In a nutshell, the vaccine is non-sterilizing, so it doesn't kill the WuFlu, it just hides the symptoms slightly for 4 months (then leaves the victim with a ruined immune system).
What this means is that the vaccinated become super spreaders. If they catch the WuFlu during the 4 month period, they have less symptoms, so they carry on their life as normal, passing the WuFlu onto others in the process.
In a nutshell, the vaccine is non-sterilizing, so it doesn't kill the WuFlu, it just hides the symptoms slightly for 4 months (then leaves the victim with a ruined immune system).
What this means is that the vaccinated become super spreaders. If they catch the WuFlu during the 4 month period, they have less symptoms, so they carry on their life as normal, passing the WuFlu onto others in the process.