Measles- a preventable disease and how vaccines help reduce its spread!

Figure 1: Measles, Public Health Hot Topics, Health Department, City of Cincinnati © 2025

Vaccine hesitancy in the United States along with social and political unrest, has now led to an alarming upswing of measles cases nationally and internationally.

Measles is a highly contagious airborne disease that has been successfully controlled with vaccination efforts from the last 6 decades. Before vaccinations were available in 1963, an estimated 3-4 million individuals were infected with the disease in the United States- with 400-500 deaths, 48,000 hospitalizations, and ~1000 cases with encephalitis yearly. In 1978 the CDC set a goal to eliminate measles from the United States by 1982, and by 1981, cases of reported measles were 80% lower than previously reported. Due to an outbreak of measles amongst vaccinated children in 1989, the Advisory Committee on Immunization Practices (ACIP), the American Academy of Pediatrics (AAP) and the American Academy of Family Physicians (AAFP) recommended a second dose of the vaccine for all children. The wide-spread implementation of this two-dose vaccination strategy, led to the significant decline of measles cases. With the absence of continuous spread over 12-months, in year 2000, measles was declared eliminated in the United States. [1]

Unfortunately, no country has achieved sustained measles elimination. From 2000-2019, estimated global coverage of at least the first dose of the measles vaccine increased from 72%-86%. Globally, the estimated cases of measles went from 36 million to 9 million from 2000-2022, a 75% decrease, and deaths from measles declined by 82%, from ~773,000 to ~136,000 deaths from 2000-2022. However, during the COVID-19 pandemic, vaccination rates declined to 81% and only half of reporting countries reached their surveillance goals. From 2021-2022, measles cases increased by 18% and several countries experienced disruptive outbreaks. Although vaccination coverage and global surveillance improved with post COVID-19 recovery efforts, coverage declined in several low-income countries compared to pre-pandemic rates; and years of sub-optimal immunization left vulnerable populations unprotected. [2] In 2023, the World Health Organization estimated 107,500 measles related deaths and 10.3 million infections. [3]

Understanding the disease and virus.

Measles is an infection of the respiratory system, immune system, and skin, caused by the measles virus. Highly contagious, the virus is transmitted by respiratory particles (through inhalation or contact with mucosal membranes of infected individuals) even if the air space is briefly shared. If you have measles, 90% of people close to you, who are susceptible or not immune, will become infected. An infected person can spread measles unknowingly to others even before they show symptoms, with transmission possible 4 days before and after the skin rash appears. Measles symptoms appear 7-14 days after contact, and common symptoms include high fever, cough, runny nose (coryza), red watery eyes (non-purulent conjunctivitis), and a rash that starts on the face and then spreads down the body. Diagnosis is often through a virus detection test via PCR (polymerase chain reaction) or serology (reactive antibodies screening) from collected urine and throat swab samples. [4] Measles can cause serious health complications particularly in children under 5 years of age. Common complications seen are ear infections and diarrhea, and serious complications can include pneumonia and encephalitis (brain swelling).

The Measles virus belongs to the Paramyxoviridae family and the Morbillivirus genus. Once the virus enters the respiratory system, in a receptor mediated mechanism, the infection spreads through the epithelial cells that line the respiratory tract and enters circulation via immune cells. After exposure, the virus enters an incubation period where the host remains asymptomatic, and although a defined period of symptoms isn’t established, acute measles symptoms appear within 10 days. Measles infection can affect multiple organs, and most complications arise in 4-6 weeks after the acute phase of infection. It can result in conditions such as otitis media, laryngotracheobronchitis, pneumonia, stomatitis, diarrhea, and in severe cases, death. [5] Late or delayed complications include prolonged or increased susceptibility to other opportunistic infections and development of neurological diseases- characterized by onset of progressive cerebral dysfunction over months. Initial neuropathology symptoms can involve changes in personality and deteriorating performance with periods of remission. [6]

Vaccination is the best protection

Anyone not protected against measles is at risk of infection or carrying the infection to others. Some individuals- infants losing passive immunity but too young for vaccines, young children, elderly, pregnant women, malnourished or immunocompromised people, are at a higher risk of experiencing complications from measles. Historically, measles was considered an almost invariably fatal childhood disease. The death rate in the 1920s was estimated at around 30% of all infected individuals, which improved substantially, prior to vaccines, due to advancements in healthcare and hospitalization. With vaccination, an estimated 54 million deaths have been prevented between 2000-2022, see figure 2. [2]

Figure 2. Estimated number of annual measles deaths with measles vaccination and in the absence of measles vaccination- worldwide, 2000-2022. [2]

What is the measles vaccine?

Measles virus vaccines are prepared using strains of virus that have been attenuated and are no longer virulent but retain their ability to induce immune response. With vigorous research, the vaccine formulation has been optimized to also incorporate protection against mumps and rubella. The MMR (measles, mumps, and rubella) vaccine is very safe and effective with mild side effects including soreness of arms, mild pain, temporary pain and stiffness in joints, and fever. Some individuals experience swollen glands in the cheeks or neck, but overall, most people do not have any serious side effects. The vaccine has been linked with a very small risk of febrile seizures in young children but are extremely rare and are not associated with any long-term effects. There is also no link between the MMR vaccine and autism. [7]

The recommended dosing strategy is two doses, with the first dose at age 12-15month and the second dose at 4-6 years of age before school entry. The second dose can be earlier so long as it is at least 28 days after the first dose. For adults, one dose is sufficient unless they have other presumptive evidence of immunity or lack thereof.

Concluding thoughts

Globally, the decline of MMR coverage during the COVID-19 pandemic has shown recovery, although this trend is not consistent across regions; with none achieving the recommended 95% second dose coverage. In 2022, approximately 22 million children did not receive any preventative vaccines against measles, leaving a large population of individuals at risk. [2] It is critical that healthcare providers, public health officials, local, regional and global partners employ resources to fight vaccine hesitancy and strengthen our capacity for outbreak preparedness and response to address immunity gaps for children and vulnerable people. It is essential that we accelerate vaccine recovery efforts and surveillance programs towards the end goal of regional and global elimination of measles.

References:

2. Minta AA, Ferrari M, Antoni S, et al. Progress Toward Measles Elimination — Worldwide, 2000–2022. MMWR Morb Mortal Wkly Rep 2023;72:1262–1268. DOI: http://dx.doi.org/10.15585/mmwr.mm7246a3

3. Measles cases surge worldwide, infecting 10.3 million people in 2023, CDC Newsroom https://www.cdc.gov/media/releases/2024/p1114-measles-cases.html

4. Wilson SE, Salvadori MI, Science M. Measles. CMAJ. 2024;196(15):E524. Published 2024 Apr 21. doi:10.1503/cmaj.240415

5. Endalamaw D, Nibret E, Munshea A, et al. Measles vaccine effectiveness in African children: a systematic review and meta-analysis. BMC Infect Dis. 2024;24(1):1330. Published 2024 Nov 21. doi:10.1186/s12879-024-10239-w

6. Naim, H. Y. (2014). Measles virus: A pathogen, vaccine, and a vector. Human Vaccines & Immunotherapeutics, 11(1), 21–26. https://doi.org/10.4161/hv.34298

7. Measles, Mumps, Rubella (MMR) Vaccine Safety, Safety Information by Vaccine, July 2024, CDC. https://www.cdc.gov/vaccine-safety/vaccines/mmr.html

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