Measles is a potentially dangerous disease

Posts on Facebook falsely claim that measles is “not a threat” to people in the developed world and that the MMR vaccine is “dangerous and ineffective”.

We’ve fact checked many false claims about vaccines before, and about measles as a disease recently.

Bad information can spread widely on social media, and can be harmful when people use it to make decisions about their health.

Measles can be dangerous

The posts say that measles is not a threat “as long as you’re not living in an 18th century slum with no indoor plumbing and suffering severe malnutrition”, and it is true that most measles deaths occur in less developed countries. However, it remains a threat, at least to some extent, even in the rich world.

Measles is highly contagious—“the most infectious of all diseases transmitted through the respiratory route”, according to the UK Health Security Agency (UKHSA).

Although the disease is usually mild, it does cause complications in 10-20% of cases in developed countries, including pneumonia in 1-6% of cases.

The measles virus “suppresses the reaction of the immune system to other pathogens” for several weeks or months, according to the National Institute for Health and Care Excellence (NICE).

Complications can be more severe in adults, pregnant women and infants, as well as those who are malnourished or ill.

MMR is safe and effective

The measles, mumps and rubella (MMR) vaccine protects against all three diseases. It is usually given in two doses, the first at one year old, the second at three years and four months.

NICE says: “Historical evidence shows that the measles vaccine is effective.”

According to research cited by the UKHSA “vaccination with one dose of MMR vaccine is at least 95% effective in preventing clinical measles”. However, a second dose is recommended for maximum protection.

The official source of vaccine information for health professionals, the Green Book, says: “After a second dose of measles-containing vaccine protection increases to well above 95%”.

The UKHSA says: “Over 99% of those who have two doses of the MMR vaccine will be protected against measles and rubella. Although mumps protection is slightly lower, cases in vaccinated people are much less severe.” The NHS says the second dose gives 99% protection against measles too.

Like many vaccines, MMR can produce side effects, which the UKHSA says are “usually mild and much less severe than the disease itself”. In more detail, the UKHSA says some people “develop a rash 10 to 12 days post vaccination. Individuals may have a mild fever but are otherwise well.”

There is “overwhelming evidence that MMR does not cause autism”. 

The World Health Organisation says measles vaccination averted 56 million deaths in the first two decades of this century. Most measles deaths that did occur were in “unvaccinated or under vaccinated children under the age of 5 years”.