Rubella vaccination: persistence of antibodies for up to 16 years.

Sera from 123 volunteers vaccinated six to 16 years previously with one of four rubella vaccines (Cendehill, RA27/3, HPV77-DE5, and To-336) were tested for rubella antibodies by single radial haemolysis and radioimmunoassay. By radioimmunoassay 110 (89.4%) of the vaccinees had antibody concentrations greater than the minimum immune titre (that is, greater than 15,000 IU/1), 11 (8.9%) were seropositive but had concentrations less than or equal to 15,000 IU/1, and two (1.6%) were seronegative. Eight (6.5%) were seronegative by single radial haemolysis, of whom five had received Cendehill vaccine. Six to eight years after vaccination subjects who had received Cendehill vaccine had the lowest geometric mean titre of antibody by radioimmunoassay while the subjects who had received HPV77-DE5 vaccine had the highest. Although antibody concentrations less than or equal to 15,000 IU/1 were not detected among subjects given RA27/3 vaccine six to eight years previously, such low levels were detected in two (15.4%) vaccinated 11-16 years previously. These results emphasise the importance of long-term surveillance programmes so that vaccination policies may be reviewed.