In Reply.—We appreciate the letter by Preblud et al and the opportunity to reply. Because the geometric mean titer (GMT) of our seropositive rubella vaccines was relatively low and the proportion of seronegatives high by hemagglutination-inhibition (HI) testing, we sent 57 coded negative or low-titered sera to the laboratory of Gilbert Schiff, MD, at the University of Cincinnati for comparison. In both his and our laboratories, 49 samples had HI titers <8. The GMT of the seropositive samples was 9.2 in our laboratory and 11.3 at Cincinnati.
Our HI-negative subjects also were tested for other rubella antibodies. A plaque-reducing neutralizing antibody assay in RK-13 cells showed that 41 (71%) of 58 HI-negative vaccinees had neutralizing titers <2. We then sent nine coded sera from HI-negative vaccinees to the laboratory of J. E. Banatvala, MD, at St. Thomas' Hospital and Medical School, London. By a highly sensitive radioimmunoassay (RIA) technique,
BALFOUR HH, AMREN DP. Rubella Vaccination-Reply. Am J Dis Child. 1979;133(11):1202–1203. doi:10.1001/archpedi.1979.02130110110027
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