[CentOS] Updates in same major version number ?

May be already asked, sorry so !

But what is the best method when updating between
4.4 and 4.5
or
4.4 and 4.6
or 
5.0 and 5.1

Is it ok to update only with 'yum update' cmd, with no risk ?

Thanks you for your support,
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Emmanuel Fournier - ICT