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.
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.