A passive remote loop-back method and apparatus for optical circuit verification is described. It does not cause the client to be authenticated in response subsequent requests on the connection as long as the underlying connection is not broken, the subsequent requests are on behalf of the same client, the client has not been removed from the system, the client’s password has not changed, a \u201csafety net\u201d timer has not expired, or any other policy that the server chooses to enforce. Each printhead module includes an ink delivery assembly and a printhead chip mounted on the ink delivery assembly. The multifunction machineserver system is constructed of the thus structured server and the plurality of thus structured multifunction machines. The invention further relates to a vaccine in which the recombinant neuraminidase is applied.