Progress Toward Regional Measles Elimination — Worldwide, 2000–2021

Anna A. Minta, MD; Matt Ferrari, PhD; Sebastien Antoni, MPH; Allison Portnoy, ScD; Alyssa Sbarra, MPH; Brian Lambert; Sarah Hauryski; Cynthia Hatcher, MPH; Yoann Nedelec, MPH; Deblina Datta, MD; Lee Lee Ho, MPH; Claudia Steulet, MPH; Marta Gacic-Dobo, MSc; Paul A. Rota, PhD; Mick N. Mulders, PhD; Anindya S. Bose, MD; William A. Perea; Patrick O'Connor, MD

Disclosures

Morbidity and Mortality Weekly Report. 2022;71(47):1489-1495.

Measles Case and Mortality Estimates

A previously described model^[3] for estimating measles cases and deaths was updated with 2021 measles data and United Nations 2000–2021 population estimates.^§§§ Data on case fatality from an updated systematic review and a suite of covariates with known relationships to case fatality were used in a Bayesian meta-regression modeling framework to produce estimates of measles case fatality ratios^¶¶¶.^[4] The updated estimates reflect heterogeneity among countries, years, and ages. On the basis of the revised model and 2021 data, the estimated number of measles cases decreased 72%, from 34,013,000 in 2000 to 9,484,000 in 2021; estimated annual measles deaths decreased 83%, from 761,000 to 128,000 (Table 2). However, the estimated numbers of both cases and deaths were higher in 2021 compared with those in 2020. During 2000–2021, compared with no measles vaccination, measles vaccination prevented an estimated 56 million deaths globally (Figure).

(Enlarge Image)

Figure.

Estimated number of annual measles deaths with measles vaccination and in the absence of measles vaccination — worldwide, 2000–2021*
*Deaths prevented by vaccination are estimated by the area between estimated deaths with vaccination and those without vaccination (cumulative total of 56 million deaths prevented during 2000–2021). Vertical bars represent 95% CIs around the point estimate.

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Abstract and Introduction
Immunization Activities
Surveillance Performance and Reported Measles Incidence
Measles Case and Mortality Estimates
Regional Verification of Measles Elimination
Discussion
References
Sidebar

^§§§State-space model of unobserved measles incidence during 2000–2021 generated using the following inputs from all member countries: 1) total annual reported measles cases, 2) annual MCV1 coverage from WHO-UNICEF estimates of national immunization coverage, 3) annual MCV2 coverage from WHO-UNICEF estimates of national immunization coverage, 4) annual SIAs with coverage and age targets (subnational SIAs are discounted by the proportion of the total population targeted), 5) annual total population size, 6) total annual births, and 7) list of all countries and years for which reporting was enhanced.
^¶¶¶The model fitted the reported case fatality ratios from the systematic review as a function of the following covariates: 1) gross domestic product per capita, 2) HIV prevalence, 3) maternal education, 4) MCV1 coverage, 5) proportion urban, 6) total fertility rate, 7) mortality rate among children aged <5 years, 8) vitamin A deficiency prevalence, 9) war and terrorism mortality rate, 10) wasting prevalence, and 11) measles incidence. Annual measles incidence for each country was based on this fitted state-space model. High income countries were excluded from this analysis.

Table 1. Estimates of regional immunization coverage with the first and second doses of measles-containing vaccine administered through routine immunization services, reported measles cases, and measles incidence, by World Health Organization region — worldwide, 2000–2021
Yr/WHO region (no. of countries in region)	Percentage				No. of reported measles cases^§ (% of total cases)	Measles incidence^§,¶,**
Yr/WHO region (no. of countries in region)	MCV1* coverage	Countries with ≥90% MCV1 coverage^†	MCV2* coverage	Reporting countries with <5 measles cases per 1 million population^§,¶	No. of reported measles cases^§ (% of total cases)	Measles incidence^§,¶,**
Total (all regions)
2000 (191)	72	44	17	33	853,479 (100)	145
2010 (193)	84	63	42	59	343,806 (100)	50
2016 (194)	85	61	67	64	132,490 (100)	18
2019 (194)	86	62	71	44	873,022 (100)	120
2020 (194)	83	51	72	57	159,073 (100)	21
2021 (194)	81	47	71	66	123,981 (100)	17
African
2000 (46)	53	9	5	6	520,102 (60.9)	832
2010 (46)	72	36	5	30	199,174 (57.9)	232
2016 (47)	68	34	22	49	36,269 (27.4)	37
2019 (47)	70	30	33	34	618,595 (70.9)	560
2020 (47)	69	19	40	30	115,369 (72.5)	106
2021 (47)	68	23	41	34	89,602 (72.3)	83
Americas
2000 (35)	93	63	65	89	1,754 (0.2)	2
2010 (35)	93	74	67	100	247 (0.1)	0.3
2016 (35)	92	66	80	97	97 (0.1)	0.1
2019 (35)	87	69	72	89	21,971 (2.5)	32
2020 (35)	85	43	72	97	9,996 (6.3)	10
2021 (35)	84	31	75	97	682 (0.6)	0.7
Eastern Mediterranean
2000 (21)	71	57	27	14	38,592 (4.5)	87
2010 (21)	76	62	52	38	10,072 (2.9)	17
2016 (21)	82	57	73	52	6,275 (4.7)	10
2019 (21)	83	52	76	38	18,458 (2.1)	26
2020 (21)	83	48	77	48	6,769 (4.3)	10
2021 (21)	82	48	77	52	26,089 (21.0)	40
European
2000 (52)	91	60	48	38	37,421 (4.4)	50
2010 (53)	94	83	80	68	30,625 (8.9)	34
2016 (53)	93	81	88	77	4,440 (3.4)	5
2019 (53)	96	85	92	30	106,130 (12.2)	117
2020 (53)	94	77	91	70	10,945 (6.9)	14
2021 (53)	94	70	91	91	99 (0.1)	0.1
South-East Asia
2000 (10)	62	27	3	0	78,558 (9.2)	51
2010 (11)	83	45	15	36	54,228 (15.8)	30
2016 (11)	89	64	75	27	27,530 (20.8)	14
2019 (11)	94	73	83	27	29,389 (3.4)	15
2020 (11)	88	64	80	45	9,389 (5.9)	5
2021 (11)	86	55	78	55	6,448 (5.2)	3
Western Pacific
2000 (27)	85	48	2	26	177,052 (20.7)	106
2010 (27)	97	63	87	63	49,460 (14.4)	28
2016 (27)	96	63	93	48	57,879 (43.7)	31
2019 (27)	95	70	93	41	78,479 (9.0)	41
2020 (27)	94	63	94	37	6,605 (4.2)	4
2021 (27)	91	59	91	48	1,061 (0.9)	0.6

Abbreviations: MCV1 = first dose of measles-containing vaccine; MCV2 = second dose of measles-containing vaccine; WHO = World Health Organization.
*https://immunizationdata.who.int/pages/coverage/mcv.html (Accessed September 29, 2022).
^†Denominator is the number of WHO member states.
^§https://immunizationdata.who.int/pages/incidence/measles.html (Accessed September 29, 2022).
^¶Population data from United Nations Department of Economic and Social Affairs, Population Division, 2022. Any country not reporting measles cases for that year was removed from both the numerator and denominator in calculating incidence.
**Cases per 1 million population.

Table 2. Estimated number of measles cases and deaths,* by World Health Organization region — worldwide, 2000 and 2021
Yr/WHO region (no. of countries in region)	No. (95% CI)		Estimated reduction in measles mortality, %2000–2021	Cumulative no. of measles deaths averted by vaccination2000–2021
Yr/WHO region (no. of countries in region)	Estimated no. of measles cases	Estimated no. of measles deaths	Estimated reduction in measles mortality, %2000–2021
Total, all regions
2000 (191)	34,012,634 (27,393,416–42,901,683)	761,038 (561,895–993,312)	83	55,812,741
2021 (194)	9,484,464 (5,681,867–14,881,517)	127,656 (74,444–197,500)	83	55,812,741
African
2000 (46)	10,965,152 (7,134,948–14,649,839)	356,299 (227,304–488,539)	81	19,499,793
2021 (47)	4,430,595 (2,619,358–7,030,815)	66,229 (38,811–106,293)	81	19,499,793
Americas
2000 (35)	8,770 (4,385–35,080)	NA^†	61	4,343,128
2021 (35)	3,410 (1,705–13,640)	NA^†	61	4,343,128
Eastern Mediterranean
2000 (21)	4,370,190 (3,295,576–6,213,952)	150,299 (115,962–205,857)	67	9,553,930
2021 (21)	2,303,170 (1,304,581–3,075,854)	48,979 (26,638–72,045)	67	9,553,930
European
2000 (52)	911,710 (733,732–1,353,344)	3,869 (3,098–4,747)	97	1,146,475
2021 (53)	86,196 (25,252–208,956)	132 (34–352)	97	1,146,475
South-East Asia
2000 (10)	12,395,953 (11,108,235–14,268,354)	224,822 (192,623–266,165)	95	16,546,297
2021 (11)	1,702,699 (1,399,591–2,321,389)	10,230 (8,328–13,538)	95	16,546,297
Western Pacific
2000 (27)	5,360,859 (5,116,541–6,381,114)	25,746 (22,907–27,993)	92	4,723,119
2021 (27)	958,395 (331381–2,230,863)	2,085 (633–5,267)	92	4,723,119

Abbreviations: NA = not applicable; WHO = World Health Organization.
*The measles mortality model used to generate estimated measles cases and deaths is rerun each year using the new and revised annual WHO-UNICEF estimates of national immunization coverage data as well as updated surveillance data. In 2021, data on case fatality from an updated systematic review and a suite of covariates with known relationships to case fatality were used in a Bayesian meta-regression modeling framework to produce estimates of measles case fatality ratios; therefore, the estimated number of cases and mortality estimates for 2000–2020 in this report differs from previous reports.
^†Estimated measles mortality was too low to allow reliable measurement of mortality reduction.