Measles – global outbreaks stemming from a decline in routine vaccine coverage
26 Mar 2025
Written by Dr Bhavya Balasubramanya
Reviewed by Dr Maya Cherian
History
Measles is a highly contagious, vaccine-preventable infectious disease capable of causing large scale outbreaks in all age groups, but most commonly in children. The first scientific description of measles and its distinction from smallpox and chickenpox is credited to the Persian physician Abu Bakr Muhammad Ibn Zakariya Al Razi (860–932) in “The Book of Smallpox and Measles”.
Measles became a widespread disease following global exploration in the 16th century, with outbreaks having devastating effects on communities. In 1963, John Enders, known as “the father of modern vaccines” and colleagues, developed the first measles vaccine. Before its introduction, nearly all children contracted measles by the age of 15.
Prior to vaccination measles was endemic globally and despite vaccination averting millions of deaths, measles continues to be common in many parts of the world.
The virus
Measles virus (MV) is a single-stranded RNA virus of the genus Morbilivirus and family Paramyxoviridae. The disease is also called ‘morbili’, ‘red measles’ or ‘English measles’.
Transmission
Measles is one of the most contagious diseases in the world. It is transmitted when an infected person coughs, sneezes, breathes, or talks. As an airborne virus, it can remain in the air or on surfaces for up to two hours after an infected person leaves the area. If one person has measles, up to 9 out of 10 close contacts (people who have been exposed through direct contact, coughing, sneezing, sharing the same enclosed air space) who are not immune (unvaccinated and not previously had measles) will also become infected.
Figure 1: CDC Measles Infographic. CDC
Incubation period
The measles incubation period is approximately 10 days after infection (range 7-18 days).
Infectious period
A person with measles is infectious from 24 hours before symptom onset until four days after the characteristic measles rash appears. They are most infectious in the 24 hours before the rash appears and therefore before measles is suspected.
Figure 2: Globally reported measles cases (WHO surveillance data August 2024 – January 2025). WHO
Global epidemiology
Measles remains a leading cause of vaccine-preventable deaths in children worldwide, with particularly high rates of cases in Africa and Asia (Figure 2). More than 95% of measles deaths occur in low-income countries with weakened health infrastructure.
In 2023, 10.3 million people were infected with measles causing an estimated 107 500 deaths predominantly in children under the age of 5 years. This is a 20% increase from 2022, when 8.6 million cases were diagnosed.
In 2025, measles outbreaks continue in all regions across the world, including Vietnam and Thailand.
Measles in Australia
Australia has recorded 33 cases of measles (year to date, 2025)—primarily in returned travellers and their close contacts.
Herd immunity and vaccine coverage
To prevent outbreaks, the World Health Organization (WHO) recommends a 95% or more vaccination rate. However, no region has met this target during or after the pandemic (Table 1).
Table 1: Measles vaccine coverage rates by WHO region 2019-2023. WHO
The impact of the COVID-19 pandemic
The COVID-19 pandemic caused disruptions to vaccination and surveillance programs. Between 2020 and 2022, over 61 million measles vaccine doses were postponed or missed due to COVID-19 disruptions. Global vaccination coverage dropped from 84% in 2020 to 81% in 2021 – the lowest rate since 2008. It is estimated that measles cases rose by 18% and deaths by 43% between 2021-2022.
Clinical presentation and management
Symptoms typically begin 7–21 days after infection and include high fever, cough, runny nose, conjunctivitis (red, watery eyes), Koplik spots (tiny white dots on the inside of the mouth; see Figure 6), and a widespread rash (see Figures 3, 4, and 5) that usually starts on the face and upper neck before spreading to the hands and feet. The rash usually appears 14-21 days after exposure and lasts for 5–6 days before fading.
Figure 7: Infographic depicting the symptoms of measles. WHO
Complications from measles commonly include ear infections and diarrhoea. Some people, however, will develop severe complications which can lead to death, including:
- Pneumonia
- Respiratory failure
- Pregnancy-related complications (e.g., miscarriages, premature labour, low birth weight infants)
- Encephalitis (swelling of the brain)
When encephalitis occurs, long-term complications can include blindness, deafness, and intellectual disability.
Public health
Testing
Early detection is critical due to the high contagiousness of measles. Testing includes:
- Nose (Nasopharyngeal) or throat swab (RT-PCR)A - within 0-3 days of symptom onset
- Urine sample (RT-PCR)A - within 10 days of rash onset
- Blood test (serum for IgM antibodies)B - detectable 6-8 weeks after acute measles
A RT – PCR: Real-time polymerase chain reaction
B Immunoglobulin M
Case management
- Infected individuals should stay home until they are no longer contagious, which is usually four days after the rash appears. This includes exclusion from work, school and child care.
- Doctors, hospitals, laboratories must report cases to public health authorities. Schools and childcare centres should notify their local public health unit as soon as they become aware of a measles case at their school or facility.
Contact tracing and prevention
Public health measures for close contacts in Australia:
- Vaccination or normal human immunoglobulin (NHIG) for non-immune contacts, where indicated
- Symptom monitoring and telephone-based healthcare access to prevent further spread.
Vaccination
Measles is a vaccine preventable-disease, with two doses of a measles containing vaccine (MCV) providing up to 99% protection.
The lack of recovery in measles vaccine coverage in low-income countries following the pandemic is an alarm bell for action. Measles is called the inequity virus for a good reason. It is the disease that will find and attack those who aren’t protected.
Kate O’Brien, WHO Director for Immunization, Vaccine and Biologicals.
Figure 8: Infographic - Get vaccinated against measles. WHO
Australia’s Measles, Mumps, and Rubella (MMR) Vaccine Program:
- The MMR vaccine is free in Australia under the National Immunisation Program for eligible infants, children, adolescents and adults.
- Those born before 1966 are likely immune due to prior exposure to measles when it was a commonly circulating disease.
- Contraindications: Pregnant individuals and those with immunodeficiency, as it is a live vaccine.
Outbreak response
Measles outbreaks occur when cases exceed normal levels in a population, timeframe, or location. Australia achieved measles elimination status in 2014 thus one case of locally acquired measles is considered an outbreak.
Pillars of response to an outbreak of measles
An outbreak is the occurrence of disease cases in excess of normal expectancy in a particular timeframe or geographic location or population. The primary goal of outbreak response is control and prevention of further transmission, thus preventing significant morbidity and mortality. Measles outbreaks can be devastating particularly in disaster and emergency settings.
The following are pillars of outbreak response which, although outlined in a linear fashion, would be occurring concurrently:
- Prepare for field work and prepare team
- Consider a rapid outbreak response team (RRT)
- Establish the existence of an outbreak
- Verify the diagnosis – clinical and laboratory confirmation
- Specimen collection for laboratory confirmation
- Construct a definition of the outbreak
- Active case finding
- Find cases systematically and record information
- Interview cases
- Descriptive epidemiology
- Generate and test hypothesis
- Implement control and prevention measures
- Case and contact management – isolation, exclusion and protection of non-immune susceptible contacts with vaccine or immunoglobulin within window period
- Education
- Determine vaccine coverage in affected areas
- Enhance surveillance
- Communicate findings considering principles of risk communication
- Reporting
- Summarise outbreak and provide a report.
Figure 9: Model for measles outbreak response. PubMed Central
I – Immune S – Susceptible IG – Immunoglobulin PEP – Post exposure prophylaxis
These pillars form the foundation of any effective outbreak response, as demonstrated by AUSMAT's deployment to Samoa in 2019 in response to a measles outbreak. Their involvement showcased the importance of a coordinated and well-structured response. Read more about AUSMAT's deployment to Samoa and their role in supporting the measles outbreak response in: Samoa measles response in retrospect: lessons that prepared AUSMAT for the COVID-19 pandemic.
Global initiatives
The increase in measles outbreaks and deaths is staggering, but unfortunately, not unexpected given the declining vaccination rates we’ve seen in the past few years... Measles cases anywhere pose a risk to all countries and communities where people are under-vaccinated. Urgent, targeted efforts are critical to prevent measles disease and deaths.
John Vertefeuille, Director of CDC Global Immunization Division
Figure 10: Number of lives saved by vaccination (1974 – 2004). Gavi, the Vaccine Alliance
The Measles and Rubella Partnership (M&MP) is a global initiative to stop measles and rubella. It was founded by the United States Centers for Disease Control and Prevention (CDC), WHO and partners with the American Red Cross, the Bill & Melinda Gates Foundation, United Nations Foundation, United Nations Children’s Fund) UNICEF and Gavi, the Vaccine Alliance. In line with Immunization Agenda 2030 and Measles and Rubella Strategic Framework 2030, the partnership aims to improve measles surveillance, increase routine immunisation coverage with two doses of MCV globally and strengthen outbreak preparedness and response.
Figure 11: © CDC. Created in 1981, this CDC poster urged parents to vaccinate their children against measles (rubeola virus) to help prevent its spread. WHO
References:
CDC | History of Measles | Measles (Rubeola)
CDC | Global Measles Outbreaks
Gastañaduy PA, Banerjee E, DeBolt C, Bravo-Alcántara P, Samad SA, Pastor D, Rota PA, Patel M, Crowcroft NS, Durrheim DN. Pubished 11 July 2018. Public health responses during measles outbreaks in elimination settings: Strategies and challenges. Hum Vaccin Immunother. DOI: 10.1080/21645515.2018.1474310.
PubMed Central | Measles virus: A pathogen, vaccine, and a vector
World Health Organization | History of measles Vaccine
World Health Organization | Measles vaccination coverage
World Health Organization | Measles and Rubella Global Update March 2025
