A recent report from the World Health Organization (WHO) and the U.S. Centers for Disease Control and Prevention (CDC) notes an alarming rise in measles cases and deaths globally in 2022. In just one year, reported cases increased 18 percent and deaths rose by more than 40 percent, meaning that nearly 150,000 people, primarily children, died due to measles infection. The increase in measles cases and deaths can be directly linked to decreased measles vaccination coverage, which saw a significant drop in 2020 and 2021 during the early phase of the pandemic. While the most recent World Health Organization -UNICEF Estimates of National Immunization Coverage data showed some recovery in global immunization coverage in 2022, that year at least 22 million children still missed the first dose of measles vaccine. In 2023 measles outbreaks in Yemen, India, Pakistan, Ethiopia, Kazakhstan, and Nigeria have been particularly concerning. Increasing funding for immunization services; strengthening the capacity of health systems to deliver vaccines; improving people’s understanding and acceptance of measles vaccines; and introducing new vaccine storage and delivery technologies that can make it easier to reach remote communities with immunization services can help improve the outlook for measles in 2024.
Q1: What is measles, and what steps has the international community taken already to prevent it?
A1: Measles is a highly transmissible, vaccine-preventable viral disease that can cause fever, rash, and diarrhea, among other symptoms. It can lead to blindness, hearing loss, secondary infections, such as pneumonia, and death, particularly for unvaccinated children in low-income countries with fragile health systems. Vaccines to protect against infection with measles have been available since the early 1960s and were introduced worldwide during that decade, but until the early twenty-first century they were not widely available outside of high- and middle-income settings. As a consequence, in the years prior to 2000 there were millions of measles cases and at least 750,000 deaths per year, more than five times the number of deaths due to measles in 2022.
Beginning in 2000, several international efforts began to focus attention on opportunities to eliminate measles, with vaccination, along with testing and disease surveillance, a core component of elimination strategies. Gavi, the Vaccine Alliance, was created in 2000 to assist low-income countries in purchasing and delivering vaccines, including measles vaccine. And the Measles Rubella Partnership, launched in 2001, brings together multilateral agencies, nongovernmental organizations, and government agencies, including the CDC, to focus attention on surveillance, immunization, training, and data analysis with respect to measles and rubella, a viral infection also known as German measles that can be prevented with a vaccine commonly administered alongside the measles vaccine. Within the Sustainable Development Goals to which countries committed in 2015, SDG Target 3.b emphasizes equitable access to vaccines as a key indicator.
Q2: Why is measles vaccine coverage important for protecting global health security?
A2: Because measles is so contagious, at least 95 percent of the population must have immunity to the virus in order to prevent deadly outbreaks. As one vaccine dose does not quite provide full immunity, the WHO recommends countries provide children with two doses, with the first at nine months to one year of age and a second at 15 to 18 months. Measles vaccine coverage thus serves as an indicator of children’s access to the health system and routine immunization services during the first few years of life. And while it is possible to initiate special activities during an outbreak to immunize people who may have previously missed the measles vaccine, supplementary immunization activities (SIAs) require additional resources and emergency campaigns can be time-consuming. Recent outbreaks have shown that the travel of one infected person to another community or country where there are unvaccinated people can spark disease transmission there as well. A case of measles also leaves the patient immunosuppressed and more vulnerable to other infectious diseases for several years following infection.
The efforts by Gavi, the Measles-Rubella Partnership, and others to raise awareness of the role vaccines can play in eliminating measles led to a significant increase in the percentage of countries offering the first dose of vaccine, from 72 percent in 2000 to 86 percent in 2019. U.S. agencies, including the CDC and the U.S. Agency for International Development, play an important role in helping to increase global measles vaccination coverage, through support for Gavi and through the provision of bilateral technical assistance to support countries’ efforts to improve the delivery of measles vaccines. Following the widespread introduction of measles vaccines, there was an estimated 75 percent drop in cases from 2000 to 2022, averting 57 million deaths.
Unfortunately, coverage of the first dose of measles vaccine decreased during the first years of the pandemic to 83 percent and has not yet recovered to the pre-pandemic levels. Gavi support has enabled eligible countries to introduce the second dose of measles vaccine, with just six countries not having introduced the second dose at this point. Coverage with the second dose, at 74 percent, remains suboptimal, leaving children in countries with lower than recommended coverage—or with pockets of low coverage—vulnerable to measles infection.
