Twelve children vaccinated with RA 27/3 vaccine showed no significant change of hemagglutination-inhibition antibody titer for ten months. They were challenged with unattenuated rubella virus. Booster responses occurred in two children and virus was not isolated from blood or pharyngeal specimens of 11 demonstrating seroconversion after vaccination. Virus was isolated from one who failed to convert after receiving RA 27/3. All remained symptomless during 28 days of observation. Four naturally acquired seropositive children challenged with unattenuated virus did not show signs or symptoms of rubella. Two exhibited a booster response after challenge. Fourteen of 22 rubella seronegative children demonstrated seroconversion after intranasal administration of challenge virus. All developed retroauricular and/or post-occipital lymph node enlargement with a mean onset and duration of 9 and 13 days, respectively. Typical rubella rash occurred only in six children, and rubella virus was isolated from throat swab specimens of ten, with a highest rate of isolation on days 16 and 18 after challenge. Viremia was demonstrated only in five, all but one of whom also had a positive isolation from pharyngeal specimens.
Naficy K, Nategh R, Ahangary S, Mohsenin H. Artificial Challenge Studies in RubellaUtilization of RA 27/3 Rubella Vaccinees, Rubella Naturally Acquired Seropositives, and Rubella Susceptible Children. Am J Dis Child. 1970;120(6):520–523. doi:10.1001/archpedi.1970.02100110068006