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The effects of a live attenuated influenza vaccine and subsequent challenge with virulent influenza virus on the delayed hypersensitivity skin test, and the in vitro response of lymphocytes were evaluated. Volunteers were skin tested before and after administration of vaccine or placebo and challenge with PPD (a purified protein derivative of Mycobacterium tuberculosis), candida, mumps, and trichophytin, and their lymphocytes were tested for [3H]thymidine uptake in response to phytohemagglutin. Of eight volunteers who showed evidence of viral replication after administration of the attenuated vaccine, four had a significant diminution in their skin test response, whereas 8 of 13 volunteers infected with virulent influenza virus showed a diminution. Of the 21 volunteers who were infected with either attenuated or virulent influenza virus, 12 showed suppression of their phytohemagglutin response. None of the volunteers who were given placebo vaccine, or who showed no evidence for viral replication after immunization or challenge, had a suppression of their skin test or phytohemagglutin responses. Although most of the infected volunteers demonstrated suppression of their T-cell function, there was no evidence of a similar suppression of B-cell function.

The efficacy of various routes of administration of the live attenuated rubella virus vaccine was evaluated by using 46 seronegative volunteers who were divided into 4 vaccine groups: subcutaneous, nosedrops, spray into posterior oropharynx and nose using large particle aerosol, and inhalation of small particle aerosol through the mouth. Seroconversion was observed in all of the vaccinees regardless of route of immunization. Nasal secretion antibody 6 weeks after immunization was highest in the volunteers who received the vaccine by nose drops (all members of this group had demonstrable nasal secretion antibody after immunization). Only half of the volunteers in the subcutaneous group developed demonstrable nasal secretion antibody. This suggests that nasal secretion antibody was best stimulated when vaccine was given directly into the nose. Volunteers were challenged with the vaccine intranasally at 6 to 8 weeks. None of the volunteers exhibited clinical symptoms or fourfold or greater serum antibody rises after challenge, but fourfold or greater nasal secretion antibody rises were observed in three volunteers in the subcutaneous vaccine group and two in the aerosol group, suggesting that those volunteers had not been protected against challenge. Rubella virus was isolated 8 to 12 days after challenge in two persons in the subcutaneous group and three in the aerosol vaccine group, but none in the nose drops or spray groups. Thus, protection after nasal challenge appeared to be best in those groups which also had the best nasal secretion antibody response after immunization. However, protection did not seem to be correlated with either nasal secretion or serum antibody levels.