Minor updates like a,b,c,d are always supported by veeam.
Anton told in his newsletter to install Update 3a, because of the thin provisioning bug:
Onto the Veeam news next! Our QC has just completed the full testing cycle of VMware vSphere 7.0 Update 3 and we're now ready to declare its official support with the current version of Veeam Backup & Replication 11a. However, be aware that the original U3 build has a regression which can consistently cause PSOD on multiple hosts in cluster. This issue really plagued one of our labs to the point where we had to stop using it for testing completely. Luckily, right when we finally finished our testing on Friday, VMware dropped the new Update 3a build which supposedly addresses this issue. So be sure to download and use this newer vSphere build instead of the original one! As someone just told me, it always pays to wait for the official support by Veeam before upgrading to a newer vSphere version – albeit always for a different reason.