Risk of Rubella Infection with Positive IgG from 6 Months Ago
If you had a positive rubella IgG test 6 months ago, your risk of acquiring rubella infection is essentially zero—you are immune and protected. 1
Understanding Your Immunity Status
Laboratory evidence of rubella IgG antibody is considered reliable proof of immunity to rubella. 1 This means:
- Any antibody level above the standard positive cutoff value of the assay is considered evidence of immunity 1
- Postinfection immunity to rubella appears to be long-lasting and is probably lifelong 1
- Your positive IgG from 6 months ago indicates you are protected against rubella infection 1
Duration of Protection
Vaccine-induced and natural immunity provide long-term, probably lifelong protection. 1 The evidence shows:
- Available follow-up studies indicate that vaccine-induced protection is long-term, probably lifelong 1
- Clinical efficacy studies demonstrate that greater than 90% of vaccinees maintain protection against both clinical rubella and viremia for at least 15 years 1
- Although data from several studies indicate that levels of vaccine-induced rubella antibodies may decline with time, surveillance data suggest that waning immunity with increased susceptibility to rubella disease does not occur 1
What About Reinfection?
While reinfection can theoretically occur, it is extremely rare and clinically insignificant. 1 Key points:
- Re-exposure to natural rubella occasionally leads to reinfection without clinical illness or detectable viremia 1
- The risk for congenital rubella syndrome among infants born to women reinfected with rubella during pregnancy is minimal 1
- Reinfection occurs without symptoms and does not pose a meaningful risk 1
Important Caveats
Your positive IgG result from 6 months ago remains valid evidence of immunity—no repeat testing is needed. 1 However:
- Clinical diagnosis of rubella is unreliable and should not be considered in assessing immune status—only laboratory evidence of IgG antibody is reliable 1
- If you were pregnant and had an "equivocal" result (not clearly positive), you would be considered susceptible 1
- The only reliable evidence of immunity is the presence of serum rubella IgG antibody above the positive cutoff 1