Measles IgG (measles immunity)
An antibody test that checks whether you are immune to measles. A positive result means you are protected — from a past infection or from vaccination (usually the MMR vaccine). It is used to confirm immunity in healthcare workers, students, travellers and during pregnancy planning.
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What it measures
Measles IgG is the long-lasting antibody the immune system makes after either a past measles infection or measles vaccination (the MMR — measles, mumps, rubella — vaccine). Once present, it usually persists for years and reflects lasting immunity, so the test answers the question 'am I protected against measles?'. This matters because measles is a highly contagious and potentially serious viral illness, and immunity checks are used in several situations: confirming that healthcare workers, students or new employees are protected; checking immunity in people planning a pregnancy or with a weakened immune system; and assessing travellers or contacts during an outbreak. A positive (reactive) IgG indicates immunity. A negative or equivocal result means immunity cannot be confirmed, and vaccination is usually offered (if appropriate). A separate antibody, measles IgM, is used differently — to help diagnose a current, acute measles infection rather than to check immunity. So measles IgG is essentially an immunity and vaccination-status check, not a test for active illness.
What a high value can mean
- Immunity to measles (positive) — the protective result; from past infection or MMR vaccination.
- A documented vaccine response — often the reason it is checked.
- Past measles infection — lasting antibodies remain.
What a low value can mean
- Not immune (negative) — no confirmed protection; vaccination is usually offered.
- An equivocal result — immunity is uncertain; may be repeated or vaccination offered.
- Waned immunity — uncommon, but antibody can fall in some people.
When to discuss with a doctor
Measles IgG is checked to confirm immunity — for example before or during healthcare or laboratory employment, at university entry, when planning a pregnancy, or for a person with a weakened immune system or a traveller. A positive result is reassuring: you are protected. A negative or equivocal result means immunity is not confirmed, and the MMR vaccine is usually recommended for those who can safely have it, guided by your doctor (it is a live vaccine, so it is avoided in pregnancy and in some immune conditions). If you have symptoms of possible active measles — fever, cough, runny nose, sore eyes and a spreading rash — that is a different, urgent situation needing prompt medical assessment, not an immunity check. Mediora.AI shows measles IgG alongside other immunity markers so your vaccination status is read together; decisions about vaccination belong with your doctor.