Rubella immunity in older children, teenagers, and young adults: A comparison of immunity in those previously immunized with those unimmunized

Determining rubella immunity in pregnant Alberta women 2009–2012

“…Therefore, those women with antibodies <10 IU/mL may still be protected, particularly as no indigenous cases of rubella have been reported in Canada since 2005, and the overall incidence of rubella in Canada has decreased from 0.2 to 0.04 per 100,000 population between 1998 and 2011 [5]. Additional studies have shown that individuals with detectable antibody levels (<15 IU/mL) produce a secondary immune response following revaccination and that viremia rarely occurs [31][32][33][34], suggesting that these levels are sufficient to prevent viral infection. In light of these epidemiological studies, the NCCLS Rubella Subcommittee decreased the 15 IU/mL cutoff to 10 IU/mL in 1992 [35]; however since 1992, the cutoffs have not been re-evaluated by the subcommittee.…”

How to determine protective immunity in the post-vaccine era

“…In 1985, the Rubella Subcommittee of the National Committee on Clinical Laboratory Standards (NCCLS) set a level of >15 IU/ ml for rubella IgG antibodies as the indicator of immunity. 8 In light of further epidemiological investigations, and additional studies indicating that individuals with low levels of antibody (<15 IU/ml) produced a secondary immune response upon vaccine challenge rather than a primary immune response, 1,[9][10][11] these cut offs were revised by the Subcommittee from 15 IU/ml to 10 IU/ml in 1992. 12 However, since 1992, the rubella cutoffs have not been assessed.…”

Dilemmas and Pitfalls in Rubella Laboratory Diagnostics in Low Prevalence or Elimination Settings

“…Samples from patients testing 915 IU/ml were considered immune, and those testing G15 IU/ml were considered susceptible to infection. In 1992, this cut off was revised to 910 IU/ml following additional clinical and epidemiological studies [84][85][86][87], showing that a secondary immune response was elicited by patients with antibody levels G15 IU/ml following challenge with live-attenuated vaccine, or reinfection [88]. Using an antibody titer as a marker of immunity presents a number of diagnostic challenges: first, the numerical antibody value is known to vary between testing assays [82•], which may result in different interpretations when the same sample is tested on multiple assays.…”