combination vaccine

[zhengj2007]

'combination vaccine' should defined as
= vaccine and has role some 'combination vaccine role'

So, all the vaccine has role some 'combination vaccine role' can inferred as 'combination vaccine'.

Current there is only one asserted subClass of 'combination vaccine', 'bacterial and viral combination vaccine'. One logic axiom is 'immunizes against microbe' some
(Viruses and Bacteria).
It is not correct, since Viruses and Bacteria is disjoint class, (Viruses and Bacteria) should be null. Suggest change to
'immunizes against microbe' some Viruses and 'immunizes against microbe' some Bacteria