A nasal spray that builds up resistance to infectious diseases right in the nasal has been developed by researchers at the Albany Medical College in New York.

It affords a high level of protection against influenza virus, pneumococcal bacteria, and even bioterrorism threats like Yersinia pestis, which causes the plague. Nasal vaccines protect the pulmonary tract after pathogen exposure, which is a big benefit in the case of a bioterrorism threat or an influenza pandemic.
Dr. Dennis Metzger says,"Intranasal vaccination gets around this problem by inducing immunity in the pulmonary passage. This prevents initial infection as well as systemic complications."
Source-Medindia