Measles and rubella are vaccine-preventable viral infections that were once among the most common childhood diseases before immunisation programmes dramatically reduced their prevalence. With vaccination rates in some communities declining in recent years, understanding what these diseases are, what their complications are, and why vaccination matters provides important context for decisions about the MMR vaccine.
Healthbooq supports parents with evidence-based information on childhood vaccination, including the diseases vaccines prevent and the evidence on vaccine safety.
Measles: The Disease
Measles is caused by the measles virus, transmitted through the air — it is one of the most contagious pathogens known, with a basic reproduction number (R0) of twelve to eighteen, meaning each case can infect twelve to eighteen unvaccinated individuals. It spreads through respiratory droplets and aerosols; the virus can remain infectious in the air for up to two hours after an infected person has left the room.
The illness begins with a prodrome of high fever, cough, runny nose, and red eyes (conjunctivitis) for two to four days. Koplik's spots — small white spots inside the cheeks, pathognomonic for measles — appear briefly in this phase. The characteristic measles rash appears on day four to five, starting on the face and hairline and spreading downward to the trunk and limbs over two to three days. The rash is blotchy, red-brown, and confluent, and lasts about five to six days.
Measles is not a mild illness. Complications are common: ear infections and pneumonia occur in approximately one in ten and one in twenty cases respectively in the UK. Measles encephalitis occurs in approximately one in one thousand cases and can cause brain damage or death. Subacute sclerosing panencephalitis (SSPE) — a rare but invariably fatal degenerative brain disease — occurs years after measles infection in approximately one in eight thousand children who contracted measles under two years of age.
Deaths from measles occur even in well-nourished children in high-income countries, at a rate of approximately one in five thousand cases. In low-income countries, mortality rates are substantially higher.
Rubella: The Disease
Rubella (German measles) causes a mild illness in children — low-grade fever, a pinkish rash starting on the face, and swollen lymph nodes behind the ears and neck. It is considerably milder than measles and rarely causes serious complications in otherwise healthy children.
However, rubella infection in the first trimester of pregnancy causes congenital rubella syndrome — a severe combination of heart defects, cataracts, deafness, brain damage, and growth restriction in the unborn baby. This is the primary reason rubella vaccination is so important: protecting children prevents them from transmitting the virus to vulnerable pregnant contacts.
The MMR Vaccine
The MMR vaccine is given at twelve to thirteen months and at three to four years as a booster in the UK. Two doses provide approximately ninety-seven per cent protection against measles. The vaccine is safe and effective; the claim that MMR causes autism, based on a fraudulent 1998 paper by Andrew Wakefield, has been comprehensively refuted by studies involving hundreds of millions of children and Wakefield was struck off the medical register for research misconduct. The fear generated by this fraudulent claim has contributed to reduced vaccination rates and several measles outbreaks in the UK and globally.
Common reactions to MMR include fever and a mild rash around seven to twelve days after the first dose (reflecting live attenuated measles replication); these are normal reactions, not transmissible infection, and resolve without treatment. Paracetamol can manage the fever.
Key Takeaways
Measles is one of the most contagious infections known — a single case can infect up to eighteen unvaccinated people. Despite being vaccine-preventable, measles remains a significant cause of child mortality globally, and outbreaks continue in communities with low vaccination rates. In the UK, the MMR vaccine (against measles, mumps, and rubella) is given at twelve to thirteen months and at three to four years. The evidence that the MMR vaccine is safe and does not cause autism is overwhelming and based on multiple large-scale studies involving hundreds of millions of children. Rubella is mild in children but causes severe foetal abnormalities if contracted in early pregnancy.
