‘Canary in the coal mine’: Experts sound alarm about measles
With more than 400 reported cases and at least one death, Texas and New Mexico are in the midst of one of the largest measles outbreaks in the United States in the past 25 years.
Since childhood vaccination rates in the U.S. dipped below 95% in 2020, experts have warned that highly infectious diseases such as measles, mumps or pertussis could make a comeback. Although there have been other notable measles outbreaks in the past decade, the outbreak in Texas and New Mexico — which may have spread to Kansas, Oklahoma and Mexico — is the first time someone has died from measles in the U.S. since 2015.
“Over the last almost 25 years, we have seen small numbers of cases with two major blips,” Yvonne “Bonnie” A. Maldonado, MD, the Taube Professor of Global Health and Infectious Diseases and professor of pediatric infectious diseases, epidemiology and population health at Stanford University School of Medicine, told Healio.
Maldonado was referring to large measles outbreaks that occurred in California from 2014 to 2015 and New York City from 2018 to 2019. The outbreak that began this year in Texas and spread to New Mexico had grown to 444 cases as of March 28, mostly in unvaccinated children, making it one of the largest outbreaks since the U.S. was deemed to have eliminated endemic measles in 2000.
U.S. outbreaks since 2000 have generally involved unvaccinated people who traveled to a place where the disease is still endemic and brought it home, Maldonado noted. The U.S. would lose its measles elimination status if one of these travel-related outbreaks lasted for more than 1 year, which almost happened in the New York outbreak.
Before the measles vaccine became available in 1963, the CDC estimated that 3 to 4 million people were infected with the highly contagious virus each year, and 400 to 500 died from it.
In February, Texas health officials announced the death from measles of an unvaccinated school-aged child, the first U.S. death from measles since 2015. Less than 10 days later, an adult in New Mexico tested positive for measles after their death.
“It is very, very important to properly educate the public about the benefits, the need, the safety (of vaccines) and how this will directly impact their children’s health, as well as their own health,” Aaron E. Glatt, MD, MACP, FIDSA, FSHEA, chairman of the department of medicine and chief of the division of infectious diseases at Mount Sinai South Nassau and professor of medicine at the Icahn School of Medicine at Mount Sinai, told Healio.
Four days after the death in Texas, newly confirmed HHS Secretary Robert F. Kennedy Jr. — who has a long history of supporting anti-science views on the safety of vaccines, including the MMR vaccine — published an op-ed on the Fox News website saying the outbreak is a “call to action for all of us to reaffirm our commitment to public health.” Kennedy noted that the MMR vaccine protects not only the person getting vaccinated, but also contributes to herd immunity, which provides protection for people who are not able to be vaccinated. But he stopped short of recommending that everyone get vaccinated, calling vaccination “a personal choice.”
“We need to get out there, and we need to vaccinate,” Maldonado said. “The messaging has not been very strong from our central public health agencies, and we need to get those messages out.”
We checked in with some experts to get their feedback on the declines in routine vaccination in the U.S. and the growing measles outbreak near the Texas-New Mexico border.
Vaccination coverage ‘still pretty good’
Vaccination coverage of 95% is widely considered the necessary threshold for preventing community transmission of measles and other vaccine-preventable diseases.
MMR coverage among kindergarteners in the U.S. has dipped to 92.7% nationally, but Maldonado said she is optimistic because most states still have rates above 90%.
“Overall, our coverage rates are still pretty good,” she said. “They are over 90% for most of the country. I think our major lesson is that we need to keep childhood vaccination levels as high as possible.”
However, the number of states with 90% or higher coverage is decreasing each year. During the 2023-2024 school year, 14 states reported MMR vaccination rates below 90%. Idaho reported the lowest rates of MMR vaccination among kindergarteners in the country at 79.6%, according to CDC data.
High vaccination coverage does not guarantee that states are safe from measles outbreaks, Maldonado explained. Texas reported statewide MMR coverage of 94.3% during the last school year but is currently the epicenter of one of the largest U.S. measles outbreaks in the past 25 years. And New Mexico, which achieved 95% coverage last year, reported dozens of cases in two counties on the Texas border.
“Even if your state has a high vaccination rate, it still does not mean you do not have pockets of undervaccination,” Maldonado said. “What happens is these outbreaks — if not attended to rapidly — will start spreading into relatively higher vaccinated parts of the community.”
This was the case in New York, which was home to the largest measles outbreak since 1992, according to a 2020 article published in The New England Journal of Medicine. The state has consistently reported 95%-plus MMR coverage over the past decade, but in 2018 and 2019, 649 people in Brooklyn and Queens were infected with measles — most of whom were ultra-Orthodox Jewish residents who were not vaccinated.
Former New York Mayor Bill de Blasio announced the end of the outbreak in September 2019 — 11 months after the first cases were detected. If it had gone another month, the U.S. would have lost its measles elimination status.
In his announcement, de Blasio praised the efforts of leaders in Jewish communities for encouraging vaccinations. In Williamsburg, where the outbreak was concentrated, MMR vaccination rates rose from 79.5% in October 2018 to 91.1% in September 2019 among children aged 1 to 5, according to the NEJM report.
Similar to the outbreak in NYC, the Texas measles outbreak is concentrated in Gaines County, which has consistently had one of the highest vaccine exemption rates in the state. In the last decade, exemptions in the county have doubled among kindergarteners (7.45% vs. 17.62%) and tripled among all K-12 students (4.32% vs. 13.6%), according to Texas Department of State Health Services data.
“There is a small group of people that we are never going to get through to,” Glatt said. “Our focus should be on the people in the past who would have been vaccinating their children, and now they are not.”
Measles legislation landscape has changed
One of the first big measles outbreaks to occur after the U.S. achieved elimination status in 2000 was a cluster of 125 cases that spread at the Disney parks in California in late 2014.
According to an MMWR report, 110 patients were California residents, and 88% of them were unvaccinated or had an unknown vaccination status. Twelve were infants as young as 6 weeks old who were not eligible for vaccination, whereas 28 reported being intentionally unvaccinated due to personal beliefs.
At the time, California allowed philosophical exemptions for vaccines, but in June 2015, state legislators passed a law eliminating the option. According to CDC data, California’s measles vaccination coverage was 92.6% during the 2014-2015 school year. Today, it exceeds 96%.
According to the National Conference of State Legislatures, five states currently prohibit religious or philosophical exemptions: California, Connecticut, Maine, New York and West Virginia. Until 2023, Mississippi did as well, but the state began allowing religious exemptions in April of that year.
In February, West Virginia senators passed a bill that would introduce the option for religious and philosophical exemptions, with senators arguing that the current rules for medical exemptions are “overly burdensome.” When the bill was presented to the House Health and Human Services Committee, local outlet News and Sentinel reported that legislators removed the religious and philosophical exemption and made changes to medical exemptions instead. Their updates would protect health care providers who write medical exemption statements from disciplinary action, and it would ensure children with medical exemptions be allowed to participate in extracurricular activities — which some schools in the state currently prohibit. The committee sent the amended bill to the state’s House of Delegates.
Public health support ‘really vital’
Physicians alone cannot end a measles outbreak — it requires support from local and state public health departments to coordinate responses across health systems and disseminate information to the public, according to Matthew Washam, MD, MPH, a pediatric infectious disease physician and chief of epidemiology and infection prevention at Nationwide Children’s Hospital in Columbus, Ohio.
“Public health support and response really is vital to interrupting and stopping any ongoing measles outbreak in the United States,” he said.
Washam described how his hospital responded to a measles outbreak that began in Central Ohio in November 2022. According to an MMWR report, the state reported 85 cases in Central Ohio near Columbus between November 2022 and February 2023. All the cases occurred in children aged younger than 16 years (median age, 1 year), and 80 were unvaccinated, the report noted.
Washam said the response involved educating providers about measles — some had never seen it — and updating intake questions to identify nonspecific symptoms that could be associated with other respiratory viruses. Staff also ensured that patients suspected to have measles were roomed in a separate area of the hospital, because the virus can live in the air for up to 2 hours after an infected person passes through.
“The fact that this is such a contagious virus, and we have clinicians who may not have seen measles infections before, shows how wonderful of a vaccine MMR is,” Washam said. “But it also highlights that it does not take much for this virus to come back.”
Washam explained that it took the efforts of organizations outside the hospital to end the outbreak. According to the MMWR report, Columbus Public Health and Franklin County Public Health identified more than 700 people who were exposed to measles who were unvaccinated or whose vaccination status was unknown and asked them to quarantine. They also actively monitored nearly 450 people for symptoms, of whom 10% developed measles. They administered postexposure prophylaxis to 59 people who had been exposed.
One takeaway from the situation “is how quickly these outbreaks happen and how quickly the response occurs,” Washam said. “Usually, by the time you identify the first several cases in an outbreak, that is just the tip of the iceberg.”
Measles is the ‘canary in the coal mine’
Measles may not be the only disease to reemerge as vaccination coverage erodes, Maldonado said.
“Measles is like the canary in the coal mine because it is one of the most infectious diseases that we know of,” she said.
In areas that are chronically undervaccinated, Maldonado said there could be outbreaks of other vaccine-preventable diseases such as mumps, rubella or pertussis.
Pertussis cases quadrupled in the U.S. from the first half of 2023 to the first half of 2024, according to the CDC, and a county in Kentucky declared a pertussis outbreak in May 2024.
“Even with good vaccination, some of these diseases can come back not because the vaccine does not work, but again, because people are not vaccinated,” Maldonado said.
Washam said physicians should reacquaint themselves with the clinical presentation of vaccine-preventable diseases, so they can identify cases as soon as possible.
“Our world is small, and there is a lot of global travel, so we will continue to see these diseases,” he said.
For more information:
Aaron E. Glatt, MD, MACP, FIDSA, FSHEA, can be reached at infectiousdisease@healio.com.
Yvonne “Bonnie” A. Maldonado, MD, can be reached at bonniem@stanford.edu.
Matthew Washam, MD, MPH, can be reached at matthew.washam@nationwidechildrens.org.
References:
- CDC. Measles cases and outbreaks. https://www.cdc.gov/measles/data-research/index.html. Updated March 28, 2025. Accessed March 28, 2025.
- CDC. History of measles. https://www.cdc.gov/measles/about/history.html. Updated May 9, 2024. Accessed March 20, 2025.
- Measles outbreak in Gaines County, Texas. https://www.dshs.texas.gov/news-alerts/measles-outbreak-gaines-county-texas. Published Feb. 5, 2025. Accessed Feb. 28, 2025.
- Measles outbreak is a call to action for all of us. https://www.foxnews.com/opinion/robert-f-kennedy-jr-measles-outbreak-call-action-all-us. Published March 2, 2025. Accessed March 7, 2025.
- National Conference of State Legislatures. State non-medical exemptions from school immunization requirements. https://www.ncsl.org/health/state-non-medical-exemptions-from-school-immunization-requirements. Updated March 10, 2025 Accessed Feb. 28, 2025.
- Senate Bill (SB277) – Public health: Vaccinations. https://leginfo.legislature.ca.gov/faces/billNavClient.xhtml?bill_id=201520160SB277. Published June 30, 2015. Accessed Feb. 28, 2025.
- Senate passes vaccine exemption bill. https://blog.wvlegislature.gov/headline/2025/02/21/senate-passes-vaccine-exemptions/. Published Feb. 21, 2025. Accessed Feb. 28, 2025.
- James J. State approved 1,800 religious vaccine exemptions for schoolchildren as of September. Mississippi Today. https://mississippitoday.org/2023/10/05/religious-vaccine-exemptions-september/. Published Oct. 5, 2023. Accessed Feb. 28, 2025.
- Texas Health and Human Services. Annual report of immunization status of students 2023-2024 school year. https://www.dshs.texas.gov/sites/default/files/LIDS-Immunizations/pdf/2023-2024_Annual_Report_of_Immunization_Status_of_Students.pdf. Accessed Feb. 28, 2025.
- Tiller EC, et al. MMWR Morb Mortal Wkly Rep. 2023;doi:10.15585/mmwr.mm7231a3.
- West Virginia House Health Committee removes religious, philosophical exemptions from vaccine bill. https://www.newsandsentinel.com/news/local-news/2025/03/house-health-committee-removes-religious-philosophical-exemptions-from-vaccine-bill/. Published March 19, 2025. Accessed March 20, 2025.
- Zipprich J, et al. MMWR Morb Mortal Wklyl Rep. 2015;64(06);153-154.
- Zucker JR, et al. N Engl J Med. 2020;doi:10.1056/NEJMoa1912514.