The measles, mumps and rubella (MMR) vaccine provides long lasting protection against measles, mumps and rubella. The MMR vaccine is made from weakened forms of the natural viruses. The viruses in the vaccine are artificially manufactured in a manner that cause none or only mild symptoms. This combined vaccine makes the child’s immune system respond to viral attack so quickly and efficiently. This means that if a child is infected with the real viruses, his immune system will quickly recognize them and act to stop the infection. Benefits of combined vaccineThere is no country that recommends immunisation against measles, mumps and rubella in three single vaccines instead of one combined vaccine. The way the MMR vaccine works means it will not harm the immune system of a normal, healthy child. Only children suffering from some severe medical conditions and allergies should not have MMR. The combined MMR vaccine means your child is protected from measles, mumps and rubella as quickly and safely as possible. To immunise against each of the three diseases separately would mean six injections over a longer period of time and this could expose children to high risks of catching the disease, more risk of missing a dose completely, more risk of pain where the injections are given and more trauma for your child.MMR has been responsible for a huge reduction in measles, mumps and rubella in children in many parts of the world.When is MMR vaccine given?MMR is offered to a child at between 12 and 13 months of age after the immunity a baby gets from their mother fades. The vaccine is injected in muscles of the thigh or upper arm. A second dose is given at the same time as other routine childhood immunisations when children are aged from three years old. Teenagers who have not  had two doses of the vaccine are also being offered the MMR vaccine during their routine teenage immunisations. Although normally given at these times, if it is missed it can be given at any age.Why the the second doseThe second dose of MMR vaccine gives the best level of protection to many children.After the first dose, between five per cent and 10 per cent of children are not protected against each of the diseases because their immune system has not responded to the vaccine. After two doses of MMR, less than 1 per cent of children are left unprotected against measles. To give the public the best protection, at least 95 per cent of the population need to be immunised against the virus. Because of the children who do not respond to the first dose and those who do not attend for immunisation, this number can only be achieved with a second dose being given to every child. Almost all children who did not respond to the first dose will be protected against measles, mumps and rubella with a second dose.Dr Joseph Kamugisha is a resident oncologist in Jerusalem, Israel