How do MMR and MMRV vaccines work?

The vaccines work by injecting your child with a small dose of live, but weakened, measles, mumps,  rubella (and in the case of MMRV varicella) viruses. The weakened virus first multiplies at or near the site of injection and is then recognised by your child's immune system. The immune system responds by making antibodies against the viruses in the vaccine, just as occurs with ‘natural’ infection.

The body’s immune system ‘remembers’ these viruses, so if your child is exposed to the wild (full strength) virus in the future, the immune system can make antibodies against the virus quickly, too quickly for the virus to establish itself. This prevents your child from developing the disease.

What is in the MMR and MMRV vaccines?

MMR and MMRV vaccines contain live, weakened measles, mumps, rubella (and varicella in the case of MMRV) viruses. The weakened viruses are grown on cells from humans or chickens in the laboratory in a carefully controlled way. Refer to NCIRS Vaccine components fact sheet. 

There are several different types of MMR and MMRV vaccines available in Australia. Depending on the type they may also contain other components to keep the vaccine stable, including sugars (such as sucrose, lactose, sorbitol and mannitol), amino acids (protein-building blocks) and very small quantities of an antibiotic called neomycin.2,3

MMR and MMRV vaccines do NOT contain any mercury, formaldehyde or aluminium.

How effective is the MMR/MMRV vaccine?

The levels of effectiveness vary for the four viruses (measles, mumps, rubella and varicella) MMR/MMRV vaccines. After their first dose of MMR/MMRV vaccine:4

  • 90 to 95 children out of 100 will be immune to measles
  • 90 to 92 children out of 100 will be immune to mumps5
  • 97 to 99 children out of 100 will be immune to rubella6
  • 65 children out of 100 will be immune to any varicella and 90 to severe varicella.7

Why are children given two doses of MMR vaccine?

Two doses give your child and the community better protection.

The first dose of MMR vaccine does not protect between 5 and 10 children out of every 100 from these diseases. After two doses of MMR-containing vaccine, only 1 child in 100 is still left unprotected.

Can I delay MMR vaccination until my child is older?

To delay measles vaccination beyond the recommended time of the first dose puts your child at risk of contracting measles. Measles infection is common and has a higher risk of complications and death for children under 5 years of age.8

What should I expect after my child receives the MMR vaccine?

Soon after receiving the vaccine, your child may experience some soreness, redness or swelling on the part of their body where they received the injection. 

As the vaccine contains weakened measles, mumps and rubella viruses, your child may experience mild symptoms of these diseases, such as a rash, fever, swollen glands or joint pain. These symptoms are not infectious and tend to occur 5 to 12 days after vaccination, disappearing after 1 to 2 days.

Copyright NCIRS 2019 - Last updated 20 September 2019


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