The 2021 Global Burden of Disease (GBD) report produced by the Institute of Health Indicators and Evaluation (IHME) provides the burden data of 371 diseases and injuries in 204 countries and regions, including the prevalence, incidence, mortality, and risk factors (GBD 2021 Demographics Collaborators, 2024; GBD 2021 Risk Factors Collaborators, 2024; GBD 2021 Causes of Death Collaborators, 2024; GBD 2021 Diseases and Injuries Collaborators, 2024). All data were available to the public free of charge through the website,² including data available in previous reports, statistical modeling, and methodological information. According to GBD 2021, measles is highly contagious and mainly spreads through respiratory droplets. The typical clinical manifestations of measles include fever, cough, runny nose, conjunctivitis, oral mucosal spots, and systemic maculopapules. According to the tenth revision of the International Classification of Diseases, the code for measles is B05.

The GBD 2021 query tool was utilized to collect data on the prevalence, incidence, mortality, and disability-adjusted life years (DALYs) from 1990 to 2021 in the global measles population and among children and adolescents in BRICS-plus countries. Given the data variability, the final estimate represents the average result of 500 calculations, and the boundary of uncertainty intervals was defined by the 2.5th and 97.5th percentiles, resulting in 95% uncertainty intervals (UIs) (GBD 2021 Diseases and Injuries Collaborators, 2024). The detailed methodology and modeling process of GBD 2021 have been recorded in other related publications (GBD 2021 Causes of Death Collaborators, 2024; GBD 2021 Diseases and Injuries Collaborators, 2024). The data set used was anonymous and open to the public free of charge.

Socio-demographic index (SDI) is a composite marker of lag-distributed income per capita, average years of education, and fertility rates among females under 25 years (GBD 2021 Diseases and Injuries Collaborators, 2024). It ranged from 0 to 1, with 0 indicating the lowest development level and 1 indicating the highest level. According to the SDI value of GBD 2021, countries were divided into five SDI quintiles: low SDI, low-middle SDI, middle-SDI, high-middle SDI, and high-SDI regions.

DALYs is a comprehensive index to quantify the impact of diseases, injuries, and risk factors on health. It comprehensively evaluates the disease burden from disability and mortality, including years of life lost (YLLs) and years lived with disability (YLDs). DALYs are widely used to evaluate the disease burden.

The data used were derived from the GBD study, which has been reviewed by the Institutional Review Board of the University of Washington and is available for public inquiry. The analysis of the GBD study followed the principles of accuracy and transparency and the guidelines for health estimation reports (GBD 2021 Diseases and Injuries Collaborators, 2024).

Due to the linear relationship between age, period, and cohort, it is difficult to estimate the unique effect set for each age, period, and cohort. Therefore, the age-period-cohort model is used to analyze the temporal trends of different age groups, periods, and birth cohorts (Zhang et al., 2022), aiming to study the temporal trend of incidence or mortality with age, period, and cohort (Fan et al., 2023). The net drift reflects the percentage change in the population in 1 year, while the local drift shows the APC in each age group. The longitudinal age curve shows the specific age rate fitted in the reference cohort, and the periodic deviation has been adjusted. Periodic relative risk (RR) was adjusted by age and nonlinear cohort effect in each period compared to the reference period. Cohort RR was adjusted by age and the nonlinear periodic effect in each cohort compared to the reference cohort. RR >1 showed that this factor increased the risk of measles; RR <1 showed that this factor reduced the risk of measles. To solve the identification problem caused by the linear relationship between age, period, and cohort, the internal estimator method associated with the age-period-cohort model was employed to overcome the unpredictability of model parameters.

The Bayesian age-period-cohort (BAPC) model considers the effects of age, period, and birth cohort on disease outcomes. It uses a second-order random walk (RW 2) model to combine prior information about unknown parameters with sample data to analyze and predict the effects of age, period, and cohort on a given event (such as mortality and disease incidence) in the population (Ji et al., 2023). This model has higher accuracy in predicting the disease burden. Therefore, R-package BAPC and integrated nested Laplace approximation were leveraged to predict the burden of measles mortality and DALYs in the initial BRICS-plus countries from 2022 to 2032.

Autoregressive Integrated Moving Average (ARIMA) model is a commonly used time series analysis method. We used this model to predict the prevalence, incidence, mortality, and DALYs of measles among children and adolescents in the BRICS-plus countries from 2022 to 2032. The model can effectively capture the trend and seasonal change characteristics in time series data by integrating three major elements: autoregression (AR), difference (I), and moving average (MA). The auto.arima function was used to select the optimal model based on the Akaike information criterion, and the Ljung–Box test was used to verify whether the residual sequence was white noise.

Joinpoint and age-period-cohort analyses reveal trend characteristics, while the BAPC model clarifies the underlying drivers behind the trends. ARIMA models analyze time series data to eliminate trends and seasonal effects, revealing underlying long-term patterns while controlling for confounding factors.

In this study, the prevalence, incidence, mortality, and DALYs rates were all expressed as the predicted values per 100,000 population with a 95% UI. All analyses were performed in R software and Joinpoint Regression Program 5.3.0 (National Institutes of Health, n.d.). p < 0.05 (two-sided) inferred statistical significance.

The changes in measles-related burden to children and adolescents per 100,000 people in BRICS-plus countries and over the world (1990–2021) are shown in Table 1; Supplementary Table 1 and Figures 1, 2. Between 1990 and 2021, the global annual number of measles declined from 1701026.49 (95% UI: 600598.31 to 3702216.49) to 130392.93 (95% UI: 114767.08 to 147285.75), representing a reduction of 92%, with an average annual decrease of 6.80% (95% CI: −7.74 to −5.85). Moreover, from 1990 to 2021, the incidence, mortality, and DALYs of measles among children and adolescents were all decreased, and the EAPC was −6.80 (95% CI: −7.74 to −5.85), −8.02 (95% CI: −8.58 to −7.46), and −8.02 (95% CI: −8.58 to −7.46), respectively. The overall measles burden in BRICS-plus countries showed a significant downward trend. The prevalence, incidence, mortality, and DALYs of measles were substantially reduced in Saudi Arabia. For instance, the prevalent cases decreased from 8320.57 (95% UI: 2961.13 to 18219.85) to 33.21 (95% UI: 7.34 to 68.26), representing a reduction of 100%, with an average annual decrease of 15.20% (95% CI: −18.73 to −11.53), followed by Iran and Egypt (Supplementary Table 1 and Figures 1, 2). Brazil had a smaller decline from 1607.74 (95% UI: 1594.94 to 1619.91) to 19.05 (95% UI: 17.57 to 20.51) (Table 1; Figures 1, 2). In addition, Brazil had no significant changes in incidence and mortality, with EAPCs of −4.55 (95% CI: −16.5 to 9.13) and −5.99 (95% CI: −11.7 to 0.09), respectively.

In 2021, Ethiopia had the highest measles-associated DALYs at 124542.02 (95% UI: 64010.84 to 219173.95). In contrast, the Russian Federation reported a minimal count at 1.74 (95% UI: 0.14 to 4.41). Ethiopia also had the highest DALYs rate per 100,000 population at 21773.84 (95% UI: 11191.1 to 38318.47), while the Russian Federation presented the lowest rate per 100,000 population at 0.51 (95% UI: 0.04 to 1.31). These results showed that the burden of measles on children and adolescents in BRICS-plus countries continued to decrease (Table 1; Supplementary Figure S1; Figures 1, 2). The trends of the prevalence, incidence, mortality, and DALYs of measles in different regions over time are displayed in Figure 3. The prevalence, incidence, mortality, and DALYs of measles in the global scope and BRICS-plus countries gradually decreased. The downward trend was particularly significant in India and remained relatively stable in other countries.

Significant regional differences were observed in the link between SDI and measles burden in BRICS-plus countries. In 2021, as the SDI level improved in 204 countries and regions worldwide, the burden of measles among children and adolescents in BRICS-plus countries decreased significantly, indicating a significant negative correlation between SDI and measles. From 1990 to 2021, the prevalence of measles among children and adolescents in BRICS-plus countries showed a downward trend with the increase of SDI (R = −0.703, p < 0.001). The downward trend was most apparent when SDI was between 0.00 and 0.50; countries with high-middle SDI (e.g., Russia and China) and middle SDI (e.g., Brazil and Iran) showed lower-than-expected measles prevalence (Figure 4A). Moreover, from 1990 to 2021, the incidence (R = −0.703, p < 0.001), mortality (R = −0.687, p < 0.001), and DALYs of measles (R = −0.687, p < 0.001) were negatively correlated with SDI (Figures 4B–D).

Measles prevalence was higher globally in the under-five age group, with females (17.09 per 100,000) having a slightly higher prevalence than males (16.88 per 100,000). In BRICS-plus countries, the prevalence of measles was highest among children under 5 years, especially in Ethiopia (19.52 per 100,000 for males and 19.34 per 100,000 for females), followed by South Africa and India. Russia, on the other hand, showed the lowest prevalence. In addition, among children and adolescents in BRICS-plus countries, the prevalence rate of measles decreased with age (Figure 5A and Supplementary Table 2). The incidence rate of measles was higher in the under-five age group globally and in BRICS-plus countries. According to the data in 2021, Ethiopia showed the most new cases of measles, with males (712.52 per 100,000) slightly higher than females (705.91 per 100,000) (Figure 5B and Supplementary Table 2). The mortality rate of measles in the under-five age group was the highest in Ethiopia, followed by South Africa and India. However, the overall measles mortality rate was low globally and in BRICS-plus countries (Figure 5C and Supplementary Table 2). The analysis of DALYs rate showed a similar trend to the prevalence. DALYs rate gradually decreased with age. Ethiopia showed the largest difference in DALYs rate between sexes among children under 5 years (females 630.01 per 100,000 vs. males 820.53 per 100,000), followed by the age group of 5–9 years old (females 45.74 per 100,000 vs. males 33.97 per 100,000) and the age group of 10–14 years old (females 13.07 per 100,000 vs. males 11.88 per 100,000) (Figure 5D and Supplementary Table 2).

Joinpoint regression analysis showed a downward trend in the global prevalence of measles in children and adolescents from 1990 to 2021 (AAPC = −7.94; 95% CI: −8.58 to −7.3; p = 0.001). However, the change in the prevalence among female patients between 2008 and 2011 was not significant (APC = −1.68; 95% CI: −12.25 to 10.16; p = 0.758) (Supplementary Table 3). Incidence and prevalence showed similar trends. Notably, changes in mortality and DALYs were not significant between 2008 and 2011 for either male or female patients, while other indicators demonstrated consistent trends with prevalence and incidence (Supplementary Table 3). Figure 6; Supplementary Figure S1 present joinpoint regression analyses of the prevalence, incidence, mortality, and DALYs of measles among children and adolescents in BRICS-plus countries from 1990 to 2021. The measles burden on children and adolescents in BRICS-plus countries showed a decreasing trend. However, the burden in China, South Africa, the United Arab Emirates, and Iran fluctuated significantly over time while relatively stable in other countries. With a large population base, India showed a significant downward trend in overall disease and measles burden at all stages. Despite the overall downward trend in China, the mortality (APC = 191.88; 95% CI: 4.47 to 715.47; p = 0.042) and DALYs of measles (APC = 183.99; 95% CI: 0.28 to 704.23; p = 0.049) were increased in children and adolescents between 2019 and 2021 (Figure 6; Supplementary Figure S1; Supplementary Tables 4–13).

Most measles cases worldwide were recorded in patients under 5 years old, and a similar distribution was observed in almost all BRICS-plus countries (Figure 7A; Supplementary Figures S2A–S4A). From 1990 to 2021, the age distribution of measles cases in the world and BRICS-plus countries was relatively stable, mainly concentrated in people under 5 years old. However, with time, the prevalence, incidence, mortality, and DALYs of measles gradually declined. Among BRICS-plus countries, the number of measles cases in India and Ethiopia was relatively stable, while Russia showed a certain degree of fluctuation.

Figures 7B–D; Supplementary Figures S2B–D–S4B–D present the age-period-cohort effect estimates for measles in children and adolescents in BRICS-plus countries. Overall, cohort effects were similar in all countries. After adjusting for period effects, the prevalence and incidence of measles decreased with age in the reference cohort. Almost all countries, except Brazil, showed similar age effects. They leveled off, showing an “L-shaped” curve. In both male and female individuals, the highest prevalence and incidence of measles were found in the 0–5 age group, while BRICS-plus countries, except Brazil, showed lowered prevalence and incidence of measles after 10 years old (Figure 7B; Supplementary Figure S2B). Figure 7C illustrates the estimated cyclical effects by sex over the entire study period. Brazil and Saudi Arabia showed an overall downward trend but a slight rebound between 2017 and 2022. However, the prevalence of measles in Brazil was greatly lower in females than in males, while the opposite pattern was revealed in Saudi Arabia. Russia had the lowest prevalence of measles between 2007 and 2012; India and Ethiopia showed a clear downward trend, with the risk remaining below 1 since 2007; and the risk also remained below 1 in China, except for 2002–2007. The risk remained consistently above 1 in South Africa until 1997 and stabilized at 1 and below since 2002, with a slight upward trend between 2017 and 2022. Egypt consistently had a risk above 1 between 2012 and 2017, showing a slight upward trend. The United Arab Emirates primarily maintained its risk above 1, although it eventually showed a downward trend. Iran had a risk above 1 from 1997 to 2002, trending below 1 since then, and its prevalence remained stable since 2012. Supplementary Figure S2C illustrates the trend in measles incidence among children and adolescents between 1990 and 2021. The incidence in all age groups showed an almost downward trend over time. In particular, the incidence was higher in the 0–5-year age group and lower in the age groups ≥10 years. Figure 7D; Supplementary Figure S2D illustrate cohort-based changes in prevalence and incidence for specific age groups. The prevalence and incidence of measles showed a gradual decrease with age. Supplementary Figures S3B–D, S4B–D illustrate changes in mortality and DALYs.

BAPC model predictions indicated that during this period, the prevalence and incidence of measles will show a downward trend worldwide. By 2032, the number of overall measles cases will reach 183319.78 (95% UI: −321397.99 to 688037.55) (Supplementary Table 14), and the number of new cases is expected to be 6273361.11 (95% UI: −11029405.35 to 23576127.56) (Supplementary Table 15). Figure 8A shows that the prevalence and number of patients in the initial BRICS countries will continue to decrease. India has the highest prevalence, followed by China, Brazil, and South Africa. In Russia, no one is expected to be infected with measles. Figure 8B shows that the incidence and number of patients in the initial BRICS countries will continue to decrease. The incidence trend is similar in China and India, two countries with large populations, but India shows slightly severe situations. There will be a few new cases in Brazil and South Africa, while Russia shows no new cases. The ARIMA model further confirmed the overall trend in the prevalence and incidence in the five countries mentioned above (Supplementary Figure S5).

The results showed that the global measles burden among children and adolescents declined significantly during 1990–2021, with the number of measles cases decreasing from 1701026.49 cases in 1990 to 130392.93 cases in 2021, a decrease of 92%, and an average annual decrease of 6.80%. This trend may be related to the increase in global vaccination coverage and public health interventions (Leong and Wilder-Smith, 2019; Auzenbergs et al., 2023). However, there was no significant decline in the prevalence of measles in female patients during 2008–2011, and mortality and DALYs also stagnated, which may be related to the contraction of public health investments in low- and middle-income countries (Andrietta et al., 2020; Addis et al., 2024). The burden of measles in the BRICS-plus countries also showed a significant downward trend. Saudi Arabia showed the most significant decrease in measles prevalence, which reached 100%, with an average annual decrease of 15.20%; in Brazil, the average annual decrease in measles prevalence was 4.09%. Ethiopia showed the highest DALYs (124542.02); the Russian Federation showed the lowest DALYs with only 1.74, indicating that low-income country Ethiopia suffers from a heavy burden of measles, while the high-income country Russia has a very low burden of measles.

Previous studies have confirmed that the risk of measles outbreaks is significantly elevated in areas with less than 95% measles vaccination coverage, leading to a surge in YLLs and YLDs (Fu et al., 2021; Gianfredi et al., 2020). Supplementary immunization targeting specific populations is effective in controlling measles incidence (Kuddus et al., 2023; Sato and Haraguchi, 2021). Between 2000 and 2017, the average annual number of deaths declined by 80% globally due to universal access to MCV (Dabbagh et al., 2018). However, millions of children missed vaccination during the COVID-19 pandemic, resulting in an 18% increase in the number of measles cases and a 43% increase in deaths globally in 2022 compared to 2021, showing signs of an epidemic rebound (Minta et al., 2023). China reported an abnormal surge in measles mortality and DALYs among children and adolescents in 2019–2021, which may be associated with a decline in routine immunization rates during COVID-19, missed vaccination of migrant children, and strained healthcare resources (Wu et al., 2020; Lee et al., 2022; Locke et al., 2023). Recent research findings (Chen et al., 2025) indicate that during the COVID-19 pandemic from 2019 to 2021, the global burden of measles decreased overall, but mortality and DALYs rates in East Asia increased significantly, with EAPC of 155.55 and 146.94, respectively. In addition, the pandemic has disrupted vaccination efforts. Among 204 countries, 75 countries reported a significant decline in the coverage rate for the first dose of MCV, and 68 countries showed a decline in the vaccination rate for the second dose of MCV. We further explored possible influencing factors by conducting a retrospective analysis of the epidemiological situation of measles among children and adolescents in China from 2019 to 2021. This included, but was not limited to, changes in vaccination coverage, population mobility patterns, allocation of medical resources, and socioeconomic factors. By comprehensively analyzing these factors, we hope to gain a more comprehensive understanding of the reasons behind the rise in measles mortality rates and provide data support and recommendations for future public health strategies. We have added the content to the discussion section. The fluctuation in South Africa may be related to the accumulation of susceptible populations, increased population density, and human immunodeficiency virus (HIV) infection, which have led to repeated outbreaks (Sartorius et al., 2013; McMorrow et al., 2009). In addition, political mismanagement and funding deficiency have negatively impacted vaccination (Pustake et al., 2022). Thus, it is evident that the measles burden is influenced by differences in healthcare resources, vaccination coverage, and socioeconomic development.

SDI is significantly negatively correlated with measles incidence and mortality (Wang et al., 2021; GBD 2015 Maternal Mortality Collaborators, 2016). This study found that the prevalence, incidence, mortality, and DALYs of measles among children and adolescents in the BRICS-plus countries declined significantly as the SDI increased. Among them, Brazil, Russia, China, and Iran had lower-than-expected measles prevalence. High-SDI country Russia (SDI = 0.82) had the lowest prevalence rate (0.01 per 100,000 population), and its vaccination coverage was more than 95%, suggesting that the measles epidemic was effectively controlled (Onishchenko et al., 2011); whereas, Ethiopia (SDI = 0.35) had a low level of economic status and lack of healthcare resources, with vaccination coverage of less than 60%, which resulted in a persistently high burden of measles. This may be closely related to its low vaccination coverage and low level of socio-economic development (Shiferie et al., 2024). Previous studies have noted that rising measles vaccination rates can significantly reduce measles incidence and mortality globally, with the most significant reductions in high-SDI countries, such as Russia and China (Gastañaduy et al., 2021; Wang et al., 2021; Wang H. et al., 2023). Consistently, the present study further confirmed the negative association between SDI and measles burden (George et al., 2024; Bidari and Yang, 2024).

The highly contagious nature makes measles a leading cause of childhood deaths globally, especially in areas with low vaccination rates (Lazar et al., 2019; Do et al., 2021; Stein-Zamir et al., 2024). About 350,000 measles cases were reported globally in 2018, resulting in about 142,000 deaths, the majority of which were in children under 5 years of age (Misin et al., 2020). The present study suggested that about 50% of global measles cases occurred in the under-five group, consistent with previous studies (Misin et al., 2020; Wang et al., 2021). This may stem from the fact that infants and young children have immature immune systems and are more susceptible to infection (Simon et al., 2015), indicating the importance of measles vaccination programs for children within 5 years after birth. Ethiopia had the highest prevalence of measles among children under 5 years of age in BRICS-plus countries, followed by South Africa and India. The study also found a significant decline in measles burden with age. DALYs in Ethiopian children under 5 years of age was 820.53 per 100,000 population for males and 630.01 per 100,000 population for females. It declined to 11.88 per 100,000 population and 13.07 per 100,000 population, respectively, in the age group of 10–14 years. This may be attributed to the cumulative effect of the mature immune system and vaccination (Simon et al., 2015; Wang Q. et al., 2023).

This study analyzed the prevalence and incidence of measles among children and adolescents in BRICS-plus countries using an age-period-cohort model. The prevalence and incidence of measles in the reference cohort showed a significant age-dependent decline, forming a typical “L-shaped” curve. The 0–5 age group had the highest prevalence and incidence of measles, which was related to the waning of maternal antibodies and the immature immune system (Simon et al., 2015; Wang Q. et al., 2023; Dagan et al., 1995). Although most countries have included the first dose of MCV in the routine immunization program for infants, vaccine interruptions, vaccine hesitancy, or insufficient coverage in some regions may lead to a continued high risk in this age group (Kostandova et al., 2022; Durrheim et al., 2024). Period effect analysis showed that Brazil and Saudi Arabia experienced a rebound in incidence between 2017 and 2022, which may be related to the disrupted routine immunization, vaccine hesitancy, delayed vaccination, and imported cases associated with religious gatherings during the COVID-19 pandemic (Lee et al., 2022; Packham et al., 2024; Chiappini et al., 2021; Shafi et al., 2016). The risk of measles in China, India, and Ethiopia has continued to decline since 2007, indicating the effectiveness of supplementary vaccination campaigns (Auzenbergs et al., 2023; Wang Q. et al., 2023; Shen et al., 2022). Cohort effect analysis further demonstrated that the incidence in more recent birth cohorts was significantly lower than that in earlier cohorts, confirming the cumulative protective effect of vaccination programs (Auzenbergs et al., 2023; Wang Q. et al., 2023). Therefore, precise interventions targeting the 0–5 age group are needed for measles elimination worldwide.

Predictive models of measles prevalence and incidence globally and in BRICS-plus countries for 2032 revealed the potential progress and persistent challenges in measles elimination. The predictions showed a downward trend in the global number of measles patients, but the wide range of the confidence interval, especially negative values, indicated the sensitivity of the predictive model to public health emergencies. Among BRICS-plus countries, India may maintain the highest prevalence, mainly attributed to the disparity in immunization coverage under its large population base (Panda et al., 2020; Scobie et al., 2015). Although China showed a similar downward trend, densely-populated areas may lead to local outbreaks. The predicted low incidence in Brazil and South Africa is based on the stability of the existing prevention and control systems, but the immunosuppressed state of HIV-infected children in South Africa remains a potential threat (Sartorius et al., 2013; Coetzee et al., 2014). Therefore, future public health policies should continue to increase vaccination coverage, especially in countries with a high measles burden, to further lower the incidence and mortality of measles.

Although this study provides a detailed analysis of the measles burden globally and in BRICS-plus countries, there are still certain limitations. Firstly, the GBD database has low data quality in some low-income countries, which may lead to underreporting. Secondly, the timespan (from 1990 to 2021) does not fully consider the impact of the recent decline in vaccination coverage in some countries, especially the rebound in the measles burden from 2019 to 2021, which may be related to interrupted vaccination due to the COVID-19 pandemic. In addition, this study focuses on the relationship between SDI and measles burden but does not deeply explore other influencing factors, such as the allocation of medical resources, population mobility, and changes in public health policies. These factors may have significant impacts on the measles burden in specific countries or regions. Future studies should further explore the independent and interactive effects of these factors to improve the reliability of research results.