The measles virus is highly contagious and increasingly prevalent in poor or resource-limited countries and is a major challenge facing the global health system. According to a World Health Organization report, no country has eliminated measles [6]. To our knowledge, our study is the first to document that Ibb Governorate recorded 3,898 suspected measles cases over the four-year period from 2020 to 2023. These results are similar to those of preceding studies in Yemen, which recorded 22,828 measles cases between 2018 and 2019 [13] and 41,135 suspected cases between 2020 and 2024 [22]. Moreover, other retrospective analyses conducted in various countries recorded 9, 643 measles cases in Saudi Arabia [26], 4,241 in Southeast Ethiopia [27], 11,71 in Canada [28], 306 in Taiwan [29], 401 in South Africa [30], 11,784 in Niger [31], and 26,188 in Kenya [32]. Recent observations have indicated an increase in measles cases, with the WHO European Region reporting 60,848 cases [33].
Furthermore, armed conflict has led to a significant increase in the incidence of measles (estimate = 1.131, p < 0.05), according to a negative binomial model conducted on 192 countries between 2018 and 2023 [34]. Armed conflict disrupts supply chains, leads to displacement from conflict zones, deteriorates healthcare, and reduces vaccination coverage and the flight of human resources. All of these factors contribute significantly to the increase in unvaccinated children and threaten herd immunity [35]. Significant rises in measles cases have been observed in the Democratic Republic of the Congo and Somalia as a result of ongoing armed conflicts [36]. Additionally, measles cases in Syria increased from 3,193 in the decade prior to the conflict to 30,241 cases between 2015 and 2019 [37]. Therefore, there is a need to enhance cooperation among countries around the world to develop and implement effective prevention strategies aimed at eliminating measles, with a focus on the most affected areas.
Seasonal variations do not appear to be associated with measles prevalence; however, travel periods and situations where unvaccinated individuals are confined in close living quarters, such as summer camps, have been linked to an increase in cases [10]. The current results revealed that the highest measles burden was observed in autumn, consistent with recent studies conducted in Ethiopia [27] and Nigeria [38]. This contradicts a previous report from some Yemeni governorates, which documented that most cases were recorded in summer and spring [23]. The discrepancy in the results is due to the geographic and climatic variations in the Yemeni governorates. In the study area, most people engage in daily activities more frequently during milder seasons, such as fall, which may contribute to measles outbreaks. Therefore, additional initiatives are needed to raise public awareness of the risks associated with infectious organisms and implement preventive measures during the seasons of greatest human movement.
This study showed that the cumulative incidence rate in Ibb Governorate over the past four years was 12.6 cases per 10,000 inhabitants, which is lower than the 18.8 cases per 10,000 population recorded in southern Yemen [23]. Furthermore, these results are higher than those documented in reports from China [39], Canada [28], Taiwan [29], Ethiopia [40], and EU countries [41]. These variations may be attributed to the effective programs employed in some nations to prevent and control measles outbreaks. Consequently, health institutions and healthcare workers must make greater efforts to enhance cooperation and coordinate efforts to monitor, detect, and track measles cases and implement plans to prevent its further spread.
These data revealed that males had a higher rate of measles incidence than females. This is consistent with earlier reports [27, 41, 42]. The current findings documented that children aged 0–4 years reported a higher incidence rate of measles, and these outcomes are inconsistent with those of other studies in Saudi Arabia [43], Lebanon [44], Syria [37], Kenya [32], Nigeria [38], and Canada [28]. The ongoing conflict in Yemen resulted in a lack of routine measles vaccinations for over 230,000 children in 2015, according to a WHO report [45]. Therefore, future measles outbreaks can be prevented by implementing various policies, including providing MMR vaccines to all children before school entry, covering all areas with vaccination staff, focusing on the most affected areas, and proactively addressing these issues.
In terms of the years of infection, the trend of the incidence rate of measles in the Ibb governorate increased between 2020 and 2023, from 0.7 to 6.8 cases per 10,000 people, by nearly nine-fold. A recent study in Yemen observed an increase in measles cases from 0.6 to 9.5 cases per 10,000 individuals between 2020 and 2023 [23]. Additionally, Patel et al. [7] documented a global increase of 556% in measles cases between 2017 and 2019. The COVID-19 pandemic that erupted from 2020 to 2022 revealed a major challenge to the global health system: delays or interruptions in measles vaccine supplies, increased outbreaks of preventable infectious diseases, and millions of children being exposed to the risk of measles infection [8]. The development of surveillance systems that are resilient to health and geopolitical crises is extremely important for the prompt detection and response to emerging outbreaks.
Regarding districts, the As Saddah district exhibited the highest rate of measles incidence per 10,000 population with 44.7 cases, followed by Yarim (30.6 cases), As Sabrah (24.6 cases), and Al Udayn (20.2 cases). The rise in measles cases in these impacted areas could be attributed to several factors, such as population density, the state of the economy, the timing of vaccinations, and the availability or quality of the vaccine. Further studies are needed to investigate the possible reasons behind the high measles outbreak among the most affected districts and to develop urgent solutions to avoid the consequences of this type of disease.
The number of measles-related deaths continues to increase annually worldwide, rising from 95,000 to 136,000 between 2021 and 2023, a 43% increase [6]. In the current results, the overall measles case fatality rate was 0.87% in Ibb Governorate, which is lower than reported in Yemen between 1 and 9.42% [13, 23]. Moreover, this outcome is also lower than reported at 1.6% in Saudi Arabia [43], 1.8% in Kenya [32], and 1.9% in Niger [31]. To achieve the goal of measles elimination, more efforts are needed to cover all areas of immunization campaigns and motivate communities to participate in routine childhood vaccination. It is also important to establish catch-up vaccination campaigns for adults and adolescents who have missed their earlier vaccinations.
Worldwide, the most measles-related deaths occur among unvaccinated or under-vaccinated children under the age of five. The measles virus weakens the immune system, making it less able to protect itself, which explains why children are more susceptible to this virus [3]. This analysis showed that the case fatality rate was higher among young children, consistent with previous studies in Yemen [13, 23] and European Union countries [41]. Therefore, primary healthcare should implement a stronger immunization program to guarantee that all children receive two doses of the measles vaccine.
Measles immunization coverage in Yemen increased from 37% in 2015 to 45% in 2023, indicating that over 50% of children in Yemen are susceptible to measles infection [46]. These results revealed that unvaccinated individuals had a significantly higher incidence of measles than vaccinated individuals (60.8% vs. 39.2%, respectively). This finding is similar to previous reports that documented 76–82.4% of measles cases among unvaccinated people in Yemen [13, 23], 85.7% in Saudi Arabia [43], 86% in the WHO European Region [40], and 63% in Canada [28]. There may be potential reasons for the low measles vaccine coverage in the study area, such as concerns about vaccine safety or effectiveness, a shortage of vaccine supplies in all areas, poor quality or invalid vaccines, or an error in the timing of vaccination.
Furthermore, social factors such as distrust in health services and political unrest that has led to the displacement of populations from areas of armed conflict may have played an additional role in preventing vaccination. Therefore, routine vaccination coverage for targeted age groups should be increased by strengthening healthcare infrastructure and community engagement. Vaccination campaigns should be implemented as scheduled. Supplementary vaccination campaigns targeting areas with low vaccination coverage should be launched. Mobile vaccination clinics and units should be established in underserved areas, providing vaccines at appropriate locations and times.
Strength and limitations
This comprehensive analysis of the measles epidemiological situation is the first to be conducted in Ibb Governorate, a region that has been overlooked in many previous studies. The results of this analysis will significantly contribute to bridging this critical gap and provide relevant perspectives on the actual measles situation aimed at devising and implementing effective programs to enhance measles control and prevention in the study areas. Although this report boasts numerous strengths, it has some limitations. This analysis used secondary data from government health offices, which might not be complete or accurate because data quality and case reporting vary from district to district. Moreover, this study relied on passive surveillance, which could lead to underreporting of cases and possibly compromise the accuracy of our findings. In addition, there may be underreporting of measles cases, which could lead to inaccurate estimates of the prevalence of this disease. Furthermore, vaccination data may be incomplete, which could potentially impact the precision of the results and the estimates of vaccination efficacy. Additionally, this analysis was unable to assess factors such as economics and environment that are associated with measles prevalence, which will add further significance to the findings.