Is vaccine-induced immunity equivalent to natural immunity?
As with other viruses, vaccine-induced immunity to rubella is not as durable as natural immunity. Peak vaccine-induced titers in children generally are lower and wane faster than titers following natural infection (13, 14), although one study showed a parallel decrease in titers (15). In a Finnish study, after administration of two doses of vaccine at 14 18 months and 6 years of age, titers were maintained at more than 15 IU/ml for 10 years in all 132 children but waned to 5 15 IU/ml at 15 years postvaccine in approximately one third of the children (51). In Sweden, vaccine-induced immunity (as indicated by a hemagglutination inhibition titer of 1:8 or greater) was shown to persist for 16 years in 94 percent of 190 girls immunized with a single dose at age 12 years (52). Another study showed that the 5 percent of subjects who lacked immune hemagglutination inhibition titers 11 years postimmunization all had neutralizing antibodies, suggesting that they might have had immunity to rubell
