means that it's not a major mutation away from it's current form...

means that it's not a major mutation away from it's current form so should still be sensitive to vaccination - but has picked up a domain mutation which is associated with a greater amount of viral load(you are getting hit with a virus machine gun instead of a glock)in the lungs - this is associated with cytokane storm -an immune reponse by the body which overreacts and floods the lungs with a foamy mix of blood and fluid leading to multi-organ failure and sudden death - much as described in 1918.
This is why all eyes have been on ukraine and surrounding countries - time will tell how bad the domain change is and wheather it will spread thru rest of world or be limited to affecting regional areas. Other mutations are likely to follow once the virus has properly circumnavigated the world population and comes under pressure from heard immunity-ie once a third of pop or so is immune either thru vac or having had mild form- a natural advantage is infered upon any mutated subspecies as there is no longer as much competition from the existing swine flu-at least thats one way to look at it- it's a big topic (pressure for viruses to gain an advantage and spread)