Rubella (German measles) IgG

Rubella (German measles) is a viral infection that is usually mild, but is dangerous for an unborn child if the mother catches it in the first half of pregnancy. After an infection or after the MMR vaccine (mumps, measles, rubella), the immune system makes IgG antibodies against the virus; after an infection they remain present for life. This test measures those IgG antibodies. The laboratory reports the amount in IU/ml; according to the LCI guideline (RIVM), most laboratories and the WHO use 10 IU/ml as the threshold for protection.

• Protection (immunity) against rubella through vaccination or a past infection
• No or too few antibodies, for example in women who have never been vaccinated and want to become pregnant

With a negative result and no vaccination, the GP can give an MMR vaccination, preferably at least one month before a pregnancy; after the vaccine you need to avoid pregnancy for 4 weeks, and during a pregnancy vaccination only takes place after giving birth. With a negative result after one earlier vaccination, a second vaccination can be considered, but after two vaccinations not, according to the LCI guideline (RIVM); checking antibodies after vaccination is not needed. Rubella is notifiable (group B2), but a positive IgG points to protection and is no reason for a notification.

According to the screening policy in the LCI guideline (RIVM) on rubella, the IgG test distinguishes well between who is and who is not protected in people who have never been vaccinated. In vaccinated people, the test is less suitable: after vaccination, the amount of antibodies is lower, so the test is more often negative while there is protection. According to the guideline, there is actually no good measure of protection in vaccinated people, and testing vaccinated people is not considered necessary. The threshold of 10 IU/ml partly depends on the test and the manufacturer.

• After vaccination, the amount of antibodies is often lower than after an infection; a negative or low result then does not mean for certain that you are not protected.
• The threshold for protection differs slightly per test and manufacturer, so results from different laboratories are not always comparable.
• IgG does not show when the infection or vaccination took place; for a recent infection, IgM or a second blood draw is needed.
• After a blood transfusion or treatment with immunoglobulins, antibodies from donors can be measured for a while.

Since vaccination, rubella hardly occurs in the Netherlands anymore: usually fewer than 5 infections per year, with an occasional outbreak among unvaccinated groups (in 2013, 57 people became ill). Vaccination coverage is between 90 and 95 percent, and about 95 percent of the population has antibodies. Protection is lower in some groups that do not vaccinate for religious reasons and in some people who came to the Netherlands as adults.

Useful for women who want to have children and are not sure whether they have been vaccinated against rubella, or know that they have not, especially if they work in healthcare or with young children, come from a country with lower vaccination coverage, or were not vaccinated for reasons of principle; they can then get vaccinated before pregnancy. In women who have demonstrably been vaccinated, the test adds little according to the LCI guideline (RIVM) and often gives a needlessly worrying result. This test is not suitable to show a recent infection; IgM or a PCR is needed for that.

• In people who have been vaccinated, the test often gives a negative or low result while they are protected; this can cause needless worry and unnecessary vaccinations.
• A positive IgG can wrongly reassure you with symptoms that look like rubella: it does not rule out a recent infection.

• RIVM-LCI-richtlijn Rodehond
• RIVM-LCI-richtlijn Rodehond, bijlage Rubella screeningsbeleid (KNOV, NVOG, NHG, NVMM, GGD, RIVM)
• NHG-Standaard Preconceptiezorg
• Preconceptie Indicatie Lijst (PIL): Rubella (rode hond)
• RIVM: Rodehond