Rubella IgG refers to a specific type of antibody produced by the immune system in response to the Rubella virus, commonly known as German measles. This article clarifies what Rubella IgG is, the reasons for its testing, how to interpret test results, and appropriate steps for managing immunity.
Understanding Rubella IgG
Rubella is a contagious viral infection caused by the Rubella virus (RuV), presenting with a rash and low fever. While often mild in children, Rubella can have serious implications, especially if contracted during pregnancy. Immunoglobulin G (IgG) is the most abundant type of antibody in the blood, playing a role in the body’s long-term defense against previously encountered pathogens.
IgG antibodies are part of the secondary immune response, generated after initial exposure to a pathogen through natural infection or vaccination. These antibodies “remember” past invaders, allowing the immune system to respond more quickly and effectively on re-exposure. The presence of Rubella IgG antibodies indicates an individual has likely had a past Rubella infection or has been vaccinated, and possesses long-term immunity.
Reasons for Rubella IgG Testing
Healthcare providers order a Rubella IgG test to assess immune status. A primary reason for testing occurs during pre-conception planning or early pregnancy screening. This is due to the potential for severe birth defects, known as Congenital Rubella Syndrome (CRS), if contracted during the first trimester of pregnancy.
Testing for Rubella IgG is also a component of routine health screenings and may be a requirement for certain school or work environments. It confirms immunity for individuals unsure if they have been vaccinated or previously infected. The test can also determine if someone has immunity following potential exposure to the Rubella virus.
Interpreting Your Rubella IgG Results
Interpreting Rubella IgG test results provides information about immunity. A “Positive” or “Reactive” result indicates Rubella IgG antibodies are present in sufficient levels, signifying immunity to the Rubella virus. This means the body can effectively fight off the virus due to a past infection or successful vaccination. A common immunity threshold is 10 IU/mL or greater.
A “Negative” or “Non-Reactive” result suggests no significant Rubella IgG antibodies were detected, indicating a lack of immunity. Individuals with this result are considered susceptible to Rubella infection. This means the person has not had the disease or vaccination, or antibody levels have declined.
An “Equivocal” or “Borderline” result means the antibody level falls into an inconclusive range, making definitive immune status determination difficult. For instance, some labs report this range as 8-9 IU/mL. In such cases, retesting after a period, 10 to 14 days, may be recommended to clarify the result.
Managing Your Immunity
Managing immunity to Rubella depends on the interpretation of your Rubella IgG test results. If your test indicates non-immunity (negative result), vaccination is recommended for protection. The Measles, Mumps, and Rubella (MMR) vaccine is a safe and effective way to achieve immunity.
For women of childbearing age not pregnant, receiving the MMR vaccine is important to prevent future Rubella infection and protect potential pregnancies. After vaccination, it is advised to avoid pregnancy for at least four weeks, as the MMR vaccine contains live, weakened viruses. One dose of the Rubella vaccine is about 97% effective at preventing Rubella.
If a pregnant individual tests negative for Rubella IgG, they are susceptible to infection, which carries risks for the developing baby. Avoiding exposure to the virus is important, and vaccination with the MMR vaccine should be deferred until after delivery. For individuals already immune (positive results), no further action is needed, as they are protected against Rubella.