This year, April 24-30 is World Immunization Week. Amid the ongoing COVID-19 pandemic, the world is paying much attention to the COVID-19 vaccines. In this context, it is important to highlight the value of basic immunizations.
Immunization is essential to preventing the spread of highly contagious diseases, many of which put infants and young children at severe risk because their immune systems are not yet fully developed. The World Health Organization (WHO) recommends basic vaccines should be given to children under the age of one against diseases such as tuberculosis, polio, rubella, diphtheria, and measles.
Measles is one of the most contagious diseases
Measles spreads easily through the coughing or sneezing of infected people. There is no known treatment for it, and vaccination is the main strategy for prevention. Unvaccinated young children are at high risk of contracting measles and its serious complications including encephalitis, blindness, severe diarrhea, severe respiratory infections, and even death. The risks of developing severe measles is generally higher for children under the age of 5 who are also malnourished or have immunological disorders such as AIDS.1
2019 had the highest recorded cases of measles in over two decades
Despite the drastic decline in the reported measles cases from 850,000 in 2000 to 132,000 in 2016, the number of annual cases has since risen sharply to 873,000 by 2019 – a five-fold increase in just 3 years.2
The increases were driven by Sub-Saharan Africa, which accounted for about 70 percent of report measles cases in 2019, followed by Europe and Central Asia (12 percent) and East Asia and Pacific (10 percent). Some countries experienced particularly large measles outbreaks, with the Democratic Republic of the Congo, Madagascar, Ukraine, the Philippines and Brazil showing the highest increases in number of reported cases (several countries from virtually zero cases in 2016) . Even in high-income countries like France, Italy, or the United Kingdom, measles cases showed 10-16-fold increases between 2015 and 2019. The United States had around 1,300 reported cases in 2019, although the country had declared measles eliminated in 2000. The WHO/ Centers for Disease Control and Prevention points out that a failure to vaccinate children on time is the main driver of the observed increase in cases and deaths.
Immunization against measles is critical
Immunization is the most effective prevention measure against measles and the vaccine has been shown to be safe and effective. The WHO recommends two doses of the measles vaccine to achieve full immunization. In many countries, the first dose is administered in a child’s first year and the second dose in the 2nd year.3
Due to the high rate of transmission, the WHO estimates that to achieve ‘herd immunity’ against measles about 95 percent of a population needs to be vaccinated. Herd immunity is achieved when enough people become immune to a disease, making its spread unlikely. Less than half of the countries in the world had met the herd protection threshold for measles by 2019. Only 82 out of 192 countries achieved a coverage of more than 95 percent for the first dose of measles vaccine, and only 52 out of 174 countries achieved a coverage of over 95 percent for the second dose of the measles vaccine.4
Globally, the immunization rate for measles has not improved much in the last decade
Globally, the proportion of children with a first dose of measles vaccines has plateaued in the last ten years, increasing only slightly from 84 percent in 2010 to 86 percent in 2019. In 7 countries over half of all children aged 1 years old had not received even a first dose of the measles vaccine in 2019: Papua New Guinea, Chad, Montenegro, Somalia, Guinea, Central African Republic, and South Sudan.
The share of children receiving a second dose of measles vaccine has steadily increased since 2000. Still, the global coverage for the second dose stood at only 71 percent in 2019 – an immunizations rate that is much lower compared with that for other diseases like tuberculosis or polio.
Several countries continue to lag severely in vaccination rates while other have made remarkable progress
Two decades ago, most children who were unvaccinated against measles were concentrated in South Asia and East Asia and the Pacific. Due to dramatic progress made by some countries including India, China, and Bangladesh, the composition of unvaccinated children has shifted drastically. Each of these countries witnessed a decline in unvaccinated children by 90 percent. For example, in 1997, there were more than 11 million unvaccinated children in India. In 2019, this number has fallen to about a million. Many children worldwide remain unprotected against measles. In 2019 globally approximately 19.8 million out of 136 million children aged 1 year old had not received a first dose of measles vaccine. These children without MCV1 are largely concentrated in Sub-Saharan Africa.
Because the first dose of measles vaccine is not always sufficient to develop protection against the disease, the addition of the second dose reinforces immunity and prevents outbreaks. Since 2017, the WHO has recommended that all countries should include a second routine dose of measles (MCV2) regardless of MCV1 coverage.
As of 2000, 93 countries provided MCV2 as part of their national immunization programs. Other countries did not provide it at all or provided it only in limited areas. However, the number of countries adopting MCV2 in the entire country almost doubled to 175 by 2019 compared to 20004. Still, many countries have low coverage of MCV2 and they are mostly located in Sub-Saharan Africa, Latin America & Caribbean, and in East Asia & Pacific. As of 2019, there were 15 countries where the coverage for MCV2 was less than 50 percent.
The impact of the COVID-19 pandemic on infant immunization programs
While measles is preventable through vaccination, this highly contagious disease is still one of the leading causes of deaths among children, especially in low-income countries. During the COVID-19 pandemic, the WHO and UNICEF have warned that immunization programs have been disrupted and many measles vaccination campaigns were or are at risk of being cancelled. To successfully prevent and eliminate measles, continued promotion and active support of two doses of measles vaccine for all children is critical.
Footnotes:
1. World Health Organization’s position paper on measles vaccines (April, 2017) :
2. Patel MK, Goodson JL, Alexander JP Jr., et al. “Progress Toward Regional Measles Elimination — Worldwide, 2000–2019.” Morbidity and Mortality Weekly Report 2020;69:1700–1705. DOI: http://dx.doi.org/10.15585/mmwr.mm6945a6
4. Calculated for economies in the WDI based on the World Health Organization’s data.5. In 2009, WHO recommended countries introduce the second dose of measles vaccine into the routine immunization schedule (MCV2) once they have achieved ≥80% coverage of MCV1 at the national level for 3 consecutive years. In 2017, however, MCV2 introduction policy was revised. WHO has recommended that all countries should include MCV2 in their national vaccination schedules regardless of the level of MCV1 coverage.