MMR vaccine vials. MMR is a combined vaccine used to prevent three diseases: measles, mumps and rubella. The first injection is given in the infant's second year, with a booster at four to six years of age. The vaccine consists of weakened samples of the three viruses, causing a weakened response from the body's immune system, which prepares defences against future infection. Measles is a potentially fatal disease. Vaccines are given as part of a childhood vaccination schedule. Combined vaccines speed up this process. These vials were produced by US multinational pharmaceutical company Merck and Co.