I agree that it is good policy to inform pet owners of when the initial rabies vaccination is considered effective, however, requiring that information to be included on the rabies certificate may create a hardship for those who utilize certificates provided by vaccine distributors or some other source of generic certificates.  Because this language requirement is specific to Virginia, national certificate printers are unlikely to comply.  I know that with the advent of computerized records in veterinary practices, many will be able to create their own certificate to comply, but for those who do not have such options, you might want to allow an alternative handout that can be provided to the clients that is not necessarily part of the certificate.