Measles outbreaks in the United States in 2025: Practice, policy, and the canary in the coalmine

1. Measles in the United States: the current situation

As of April 24, 2025, the Centers for Disease Control and Prevention has confirmed 884 measles cases in the United States; there are 11 outbreaks (defined as having three or more related cases) spread across 29 states [1]. Among these, Texas, New Mexico, Kansas, Ohio, Oklahoma, and Pennsylvania are leading. Texas predominates with 646 cases, followed by New Mexico with 65 [2,3]. Most significantly, the outbreak is concentrated along the Western Texas–Southern New Mexico border [4]. This cluster of counties holds 92.6 % of cases in Texas and all but one case in New Mexico [2,3]. Furthermore, Gaines County, Texas, alone hosts 393 cases - more than any state in the country. This cluster contributes the majority of cases in the US this year and all three deaths. The first two deaths took place in Lubbock, with both children being from Gaines County and one from the Mennonite community; the third was an adult in Lea County [[5], [6], [7]]. Importantly, all three individuals were unvaccinated [[8], [9], [10]].

These rates of measles seen so far in 2025 are unprecedented since the elimination of measles in the United States in 2000. Throughout this 25-year period, cases only rose to significant levels on two other occasions: 667 in 2014 (the “Disneyland Outbreak”) and 1274 in 2019 (centered in communities of Orthodox Jews in New York) [1]. This is especially concerning since 2019 levels have almost been surpassed in only the first quarter of this year. The US does not stand alone in these trends, as it appears measles is growing throughout the globe. In Europe, cases are currently the highest they have been in 25 years with particular concern in Romania and Kazakhstan [11,12]. For the year 2024, a total of 35 212 measles cases were reported across the EU/EEA, marking a notable increase (ten-fold), from the 3973 cases reported in 2023 [13]. In Africa, the situation is equivalent and even more concerning as no country in the region has achieved elimination [14]. While contexts differ considerably by country and region, these uniform trends are particularly concerning for global shifts in attitudes regarding vaccines [15].

2. Current risk factors for measles

Whilst this rise in measles cases in the US has been portrayed in the media as an issue of immigration of non-US citizens into the country, it has been shown that there is no correlation between the share of a state's population that is foreign born and its rate of measles [16]. The incidence of measles has become increasingly due to US-acquired cases - with most being epidemiologically or virologically linked to imported cases by US residents who have travelled to areas with high prevalence of measles [17]. Therefore, herd immunity plays a significant role to prevent the spreading of these seeding cases; at least 95 % of the population must be immune to measles as it is a highly contagious virus.

Despite decades of a good safety profile and disproven links to autism, measles vaccination rates do not reach this threshold (of 95 %) and are in fact dropping [18]. National 2-dose MMR vaccination coverage was reported to be 92.7 % during the 2023–2024 school year [19]. Yet, even this level of coverage is not observed in particular communities, with heterogeneous immunity observed in different populations throughout the country. Moreover, these vaccination rate estimations do not include homeschooled or some undocumented children, who are both less likely to be vaccinated [20,21]. It is possible, then, that vaccination rates are lower than currently estimated. This ultimately means there are numerous pockets of individuals throughout the country at high risk of contracting measles. Indeed, the CDC reports that 97 % of all cases this year have occurred in those without evidence of vaccination coverage [1].

Significantly, Gaines County, Texas, consistently holds the lowest reported levels of MMR vaccination in the state whilst having substantially higher numbers of cases [19]. These low rates can be attributed to a variety of political, social, and religious factors. Notably, the county is home to a significant Old Colony Mennonite community, distinct from the Mennonite Church of America [22,23]. This isolated group is considered to be under-vaccinated, however accurate rates are difficult to quantify since most children are either home-schooled or enrolled in nonaccredited private schools that do not record immunization data [5,24,25]. However, the situation is nuanced. While the Mennonite doctrine does not explicitly prohibit vaccinations, the Old Colony Mennonites tend to be highly conservative in their ideology [26]. They typically live with limited access to technology and modern amenities, and firmly resist assimilation into mainstream society [27,28]. This, combined with historical exclusion from earlier U.S. vaccine campaigns, contributes to skepticism towards modern medicine. Along with their isolated rural way of life, the community's strong emphasis on self-reliance distances them from access to healthcare. Interestingly, most Old Colony Mennonites speak a Low German dialect, further limiting access to healthcare [28].

The Mennonite community in Gaines can be thought of as one example of a wider spread phenomenon. This would include the communities of the Orthodox Jews in New York and Amish in Ohio, as well as clusters of vaccine exemptions in California – all of whom are under vaccinated and have experienced outbreaks of measles in the past few years [[29], [30], [31]].

The drop in vaccination rates in the past five years could be attributed to the delay and pause in routine childhood vaccinations during the COVID-19 pandemic, as healthcare resources were shifted to prioritize the pandemic and parents adhered to home quarantine [32,33]. However, rates in administration of the vaccine have continued to decrease despite the end of the pandemic [19,34,35]. As political and social discourse during the time of the pandemic focused heavily on the efficacy and safety of the COVID-19 vaccines, the conversation spilled over to include all vaccinations. Ultimately, attitudes and concerns towards vaccinations as a whole were affected [36].

The increase in vaccine hesitancy also appears in line with changing cultural and political views in the country, with beliefs against vaccine use becoming more prevalent as right-wing ideologies grow in popularity. Far-right parties often promote individual liberty and skepticism towards scientific institutions, which lay fertile ground for vaccine distrust to thrive [37,38]. This changing political climate is also occurring worldwide and may be the reason why MMR vaccine rates are dropping on a global scale. According to the World Health Organization, rates in 2021 dropped to the lowest level in the past two decades [39]. In 2023, this value is reported to have increased slightly but remains low at 83 % first-dose vaccination [40]. This net drop corroborates with the rise in measles cases observed globally, further underscoring the role that the drop in vaccination rates are playing in this global resurgence.

Growing anti-immigration rhetoric seen in both conservative and liberal domains is also thought to be impacting protection against measles. Access to healthcare among undocumented immigrants is frequently limited by cost, language, knowledge of the healthcare system, and fear of deportation [41]. As the culture of fear among undocumented individuals continues to intensify, as is occurring in 2025 in the US, larger numbers of individuals will be unable to seek healthcare and immunization [42]. Therefore, pockets of vulnerable individuals will expand. In fact, Texas is currently home to the second greatest number of undocumented immigrants in the country. While access to vaccination is fundamentally part of the human right to health, protecting these individuals will also contribute to herd immunity and the overall greater safety of the country from vaccine-preventable diseases [43,44].

3. Implications for clinicians and public health officials

Clinically, the risk of measles is often found in its complications. During the primary infection, complications such as secondary bacterial pneumonia and encephalitis are common causes of mortality [45]. Measles has also been shown to cause dysfunctional immunity, contributing to increased risk of secondary infections as well as reactivation of latent infections for up to two years [46]. This immune amnesia can increase mortality even outside of the primary infection; this is particularly concerning in regions of the world with high prevalence of other severe infections. The public health risk of this virus, and therefore necessity of intervention, must thus not be underestimated [47].

While reasons for vaccine refusal are often complex, healthcare professionals must embrace this complexity and use evidence-based strategies to improve both attitudes towards vaccination as well as vaccination behaviors [48]. On the frontlines of this work are primary care physicians, who are tasked with engaging in sustained dialogue with parents [49]. Foremost, all children with accepting parents are to be routinely vaccinated at 12 and 60 months of age. If there is significant risk of exposure, an additional vaccine can be given between 6 and 12 months before beginning the routine schedule; if risk continues to increase, the second dose of vaccine can be given only 3 months following the first to achieve maximum immunity.

While it is common practice to decline the acceptance of vaccine-refusing families into pediatric or primary care practice, there is no current evidence to show this is efficacious [50]. Vaccine hesitancy is often interlaced with social determinants of health and various socioeconomic factors; since vaccine refusal has been shown to be a modifiable behavior, multi-visit conversations are encouraged and should involve fully understanding concerns and utilizing empathic responses [51,52]. The parents’ path from pre-contemplation (not considering vaccination) to action (vaccinating) must be step-wise; placing pressure on parents or exercising judgement can halt progress towards vaccination [53]. Innovative approaches have also been developed, with success using social media platforms focused on presenting knowledge in a collaborative tone [48].

Efforts against vaccine hesitancy must also extend beyond the clinic to widespread public health efforts, particularly since religious and political factors are significantly at play [54]. As seen in Gaines, a community's religious and cultural disposition can significantly impact health decisions and vaccine rates. Campaigns encouraging vaccination must be inclusive of the unique considerations of these groups in order to be effective; this point is emphasized by the CDC [[55], [56], [57]]. Forward-thinking approaches to reach these individuals are critically needed. One case for inspiration can be found in India, where healthcare workers and faith leaders co-designed a campaign which successfully improved vaccine uptake [58].

In order to achieve protection for all children, both national and global efforts are required. This state of emergency in Gaines could have occurred in any community with enough vulnerability and hence needs to be understood as a cautionary tale. It may even be speculated that the risk of reestablishing endemic measles in the US due to this continually increasing vulnerability is now upon us [59]. Beyond this, measles has been described as the canary in the coalmine, since outbreaks expose populations who are vulnerable to all vaccine-preventable diseases [60]. With so many cases in the first quarter of the year, it can be extrapolated that vaccine-acquired immunity is currently at a record low.