The influenza vaccine is unusual in that most years a different vaccine is made. Because strains of influenza virus that circulate in the community can differ from one season to the next, the vaccine must change to best protect against those different strains.
In VMware, switches are used to establish a connection between the virtual network and the physical network. With ESX and ESXi, two different kinds of switches can be used: standard switches and distributed switches.
As you can see, a network card is what you said, but the host adapter, controls things like ethernet, firewire, iSCI, SATA, and other kinds of storage devices. You can think of it as the device that controls external ports and network devices.