Public Health Actions to Control Measles Among Afghan Evacuees During Operation Allies Welcome — United States, September–November 2021

Investigation and Results

Measles was first diagnosed in an evacuee aged 17 years who began experiencing prodromal symptoms on September 1 in Germany while awaiting transport to the United States (disclosed on later interview). The patient traveled on military flights from Ramstein Air Base, Germany to Washington Dulles International Airport (IAD) on September 3, and from IAD to Fort McCoy, Wisconsin on September 4. A few hours after completing the intake process, the patient sought care at the on-site acute care clinic with a fever of 107.6°F (42°C) and a maculopapular rash (Box). The patient was transferred to a local emergency department where specimens were collected for measles testing, which was performed by the Wisconsin State Laboratory of Hygiene. Upon return to Fort McCoy on September 5, the patient was isolated at an on-site facility. Measles was confirmed by real-time reverse transcription–polymerase chain reaction (RT-PCR) on September 5; molecular characterization yielded genotype B3, consistent with genotypes recently identified in countries neighboring Afghanistan.**

A confirmed measles case was defined as an acute febrile rash illness and either detection of measles virus RNA using real-time RT-PCR or measles-specific immunoglobulin M antibody by enzyme immunoassays, or direct epidemiologic linkage to a laboratory-confirmed case (3). By September 14, five additional measles cases had been confirmed: four in patients at hotel A and one in a patient at Fort Pickett, Virginia. To identify additional cases, active case finding and tracing of exposed contacts were conducted by DoD and DHS public health surveillance and medical staff members and contractors at domestic military bases, international airports, and hotel A. This activity was reviewed by CDC and was conducted consistent with applicable federal law and CDC policy.^††

A total of 47 confirmed measles cases were reported among Afghan evacuees at six domestic sites in four jurisdictions (22 cases in Virginia, 22 in Wisconsin, two in New Mexico, and one in New Jersey). Rash onset dates ranged from September 2 to October 15.^§§ The median age of patients was 1 year (range = 0–26 years); 16 (34%) patients were aged <12 months, 17 (36%) were aged 1–4 years, 11 (23%) were aged 5–19 years, and three (6%) were aged 20–29 years; 55% were male. All 47 patients were unvaccinated or had unknown vaccination status upon arrival in the United States. Overall, 46 (98%) cases were laboratory-confirmed. Genotyping performed on 43 real-time RT-PCR–positive specimens identified genotype B3 in all. The crude attack rate was 0.065%. Domestic sites also reported 57 varicella cases, 14 mumps cases, and one rubella case.^¶¶

Public Health Response

After DoD began larger-scale emergency evacuations, administration of routine predeparture vaccinations in Afghanistan was not operationally feasible because of the urgency and scope of the evacuations, and efforts shifted to providing MMR vaccine to evacuees soon after arrival in the United States. Following the detection of measles cases, rapid scale-up of DoD-led vaccination efforts began across domestic military bases housing evacuees on September 6, and evacuation flights from overseas locations to the United States were temporarily halted on September 10. CDC issued a directive on September 14 recommending urgent implementation of measures to limit measles spread; this directive included a pause on evacuation flights from overseas locations and the acceleration of mass MMR and varicella vaccination for all eligible evacuees aged ≥6 months and ≥12 months, respectively, who did not have contraindications (4,5), at both OAW overseas and domestic locations. Because of the lack of documentation of previous vaccination or disease history of evacuees, more targeted vaccination of susceptible persons was not possible. In addition, all evacuees were presumed to have been exposed to measles and thus were recommended to remain in quarantine (i.e., on bases and in overseas locations) for 21 days following receipt of MMR vaccine (3). Efforts were also made to provide immunoglobulin to persons ineligible for MMR vaccine (infants aged <6 months and seronegative pregnant women) at domestic sites.

By September 24, an estimated 91% of eligible evacuees at the domestic military bases had been vaccinated with MMR vaccine, increasing to 96% by November 25. No measles cases were reported in military personnel, volunteers and staff members supporting the OAW response, or in the community (areas surrounding the military bases or hotel A); no measles-related deaths occurred. OAW international flights resumed on October 5, with no measles cases identified among evacuees arriving after the pause.

An additional tool for measles control became available on September 17 with the addition of measles to the list of federally quarantinable diseases via Executive Order 14047.*** This policy change enabled the use of federal regulatory authority to control measles transmission by allowing the issuance of federal public health orders, if necessary. CDC developed operating procedures and policies to determine situations for which issuing a federal order for isolation of patients and quarantine of exposed contacts might be necessary for the protection of public health. As a result of the high measles vaccination coverage achieved through this response and the adherence with voluntary isolation and quarantine recommendations, no federal public health orders were issued.

Discussion

Measles is an extremely contagious viral illness, with one infectious patient capable of infecting an average of 12–18 persons in a fully susceptible population (6). Measles-containing vaccines are highly effective, with 2 doses conferring approximately 97% protection (4). Measles elimination^††† has been maintained in the United States since 2000; however, measles cases reached a 25-year high in 2019, with 1,274 cases reported across 32 U.S. jurisdictions; 85% of these cases occurred among pockets of undervaccinated persons, where the virus spread following international importations (7). Reduced global travel, physical distancing, and other COVID-19 pandemic-related mitigation measures likely contributed to only 15 measles cases being reported in the United States from 2020 to 2021 before the start of OAW (8). However, the lessons of the 2019 U.S. outbreaks highlight the need for vigilance as well as the importance of prompt interventions to control measles (8). In addition, global standards for humanitarian crises^§§§ recommend conducting a mass measles vaccination campaign when estimated measles coverage is ≤90% or is not known. The low measles vaccination coverage among evacuees, coupled with the high potential for multiple importations, increased risk for transmission in congregate settings, and possible spread into U.S. communities during the OAW response, demanded immediate public health action requiring a whole-of-government approach.

All identified cases occurred among evacuees who arrived during August 17–September 10 before international flights from overseas locations were temporarily halted to permit mass vaccination of all evacuees. The absence of additional cases in evacuees who arrived after flights resumed is evidence of the success of this strategy in preventing new introductions of measles into the United States. This response also highlights the effectiveness of the mass vaccination campaign in minimizing further transmission on military bases (attack rates for measles outbreaks among refugee populations in congregate settings have ranged from 0.9% to 25.5%) (9,10), as well as preventing transmission into communities with health care systems already strained by the COVID-19 pandemic. Efforts continued to 1) ensure high vaccination coverage among the remainder of incoming evacuees, 2) identify and isolate ill persons among evacuees on military bases, and 3) perform contact tracing to identify and quarantine exposed persons.

The findings in this report are subject to at least two limitations. First, cases might have been missed because of clinical misdiagnoses, limited available staff members to conduct timely and regular wellness checks, and failure of ill persons to seek care at acute care clinics. Second, contact tracing and ascertainment of exposures were difficult because of evacuees mixing at overseas locations, on international and domestic flights, at receiving airports, and at military bases, creating challenges for adequate monitoring among exposed persons.

Rapid implementation of a high-coverage mass measles vaccination campaign by DoD with a 21-day quarantine after receipt of MMR vaccine reduced measles importations and prevented substantial potential spread of measles on military bases and into U.S. communities, and the morbidity and mortality associated with such outbreaks. The robust MMR and varicella vaccination campaign also likely limited the number of varicella, mumps, and rubella cases identified across military bases.

Operation Allies Welcome Response Group

Indu B. Ahluwalia, CDC; Olubunmi A. Akinkugbe, CDC; Aaron Aranas, CDC; Melissa Arons, CDC; Christine Atherstone, CDC; Valerie Bampoe, CDC; Patricia Bessler, CDC; Leticia Bligh, CDC; Kimberly Bonner, CDC; Virginia B. Bowen, CDC; Kendra Broadwater, CDC; Gary W. Brunette, CDC; Joan M. Brunkard, CDC; Dru A. Burns, CDC; Molly Cantrell, CDC; Bryan E. Christensen, CDC; James R. Cope, CDC; Janine Cory, CDC; Nathan E. Crawford, CDC; David Daigle, CDC; Scott M. Daly, CDC; Peter Dejonge, CDC; Mushtaq Dualeh, CDC; Kevin H. Dunn, CDC; Rachel B. Eidex, CDC; Kai Elgethun, CDC; Geroncio Fajardo, CDC; Maureen Fonseca-Ford, CDC; Katherine Franc, CDC; Joanna Gaines, CDC; Nisha George, CDC; James Goodson, CDC; Caitlin Green, CDC; Aaron J. Grober, CDC; Kibrten Hailu, CDC; Duane R. Hammond, CDC; Brian H. Harcourt, CDC; Alexandra Hess, CDC; Elisabeth Hesse, CDC; Deborah V.L. Hirst, CDC; Jennifer Hornsby-Myers, CDC; Ben Humrighouse, CDC; Maliha Ishaq, CDC; Kenta Ishii, CDC; Allison James, CDC; Bina Jayapaul-Philip, CDC; Emily S. Jentes, CDC; Latoya Johnson, CDC; Marie Johnston, CDC; Christine D. Jolley, CDC; Akadia Kacha-Ochana, CDC; Harpriya Kaur, CDC; Megan Keaveney, CDC; Hilary C. Kelly, CDC; Vikram Krishnasamy, CDC; Gayathri S. Kumar, CDC; Ma’isah Larkin, CDC; Mary Layde, CDC; Ryan F. LeBouf, CDC; Deborah Lee, CDC; Rosa C. Lira, CDC; Raymond Lopez, CDC; Matthew J. Lozier, CDC; Alicia Macler, CDC; Hugh Mainzer, CDC; Deborah Malden, CDC; Jason Malenfant, CDC; Nina Marano, CDC; Zachary Marsh, CDC; Oren Mayer, CDC; Robert McDonald, CDC; Neha Mehta, CDC; Akshara N. Menon, CDC; Erika Meyer, CDC; Stephen T. Miles, CDC; Faisal Minhaj, CDC; Sara Mirza, CDC; Kyle M. Moller, CDC; Sapna Bamrah Morris, CDC; Dylan T. Neu, CDC; Lisa P. Oakley, CDC; Denisse Vega Ocasio, CDC; Taylor Osborne, CDC; Alan C. Ou, CDC; Megan Peck, CDC; start highlightClelia Pezzi, CDC;end highlight Marissa Person, CDC; Drew Posey, CDC; Alexis Pullia, CDC; Chaolong Qi, CDC; Amanda J. Raziano, CDC; Malia Richmond-Crum, CDC; Shahrokh Roohi, CDC; John M. Saindon, CDC; Samira Sami, CDC; Liliana Sanchez-Gonzalez, CDC; Ryan Schweitzer, CDC; Amee M. Schwitters, CDC; Mays Shamout, CDC; Caitlin E. Shockey, CDC; Talya Shragai, CDC; Kimberly B. Singler, CDC; Erica J. Sison, CDC; Dallas Smith, CDC; Matthew Smith, CDC; Neha J. Sood, CDC; Brittany J. Sunshine, CDC; Alma Trujillo, CDC; Snigdha Vallabhaneni, CDC; Alexandra Wickson, CDC; Jonathan S. Yoder, CDC; Laura R. Zambuto, CDC; Tara Cozzarelli, Defense Health Agency; Morrisa Rice, Health Resources and Services Administration; Madia Ricks, Health Resources and Services Administration; John S. Birchfield, North American Aerospace Defense Command and U.S. Northern Command; Atmaram Nambiar, Pennsylvania Department of Health; Avery Avrakatos, U.S. Agency for International Development; Timothy P. Ballard, U.S. Air Force; Ethan Dennis, U.S. Air Force; Kelly Gambino-Shirley, U.S. Air Force; Amanda E. Huston, U.S. Air Force; Melissa G. Jennings, U.S. Air Force; David M. Oldham, U.S. Air Force; Michael J. Rabener, U.S. Air Force; Matthew N. Fandre, U.S. Army; Raymond J. Jablonka, U.S. Army; Amber Love, U.S. Marine Corps; Olivia L. Peduzzi, U.S. Marine Corps; Kirsten Snow, U.S. Marine Corps; Joy A. Greer, U.S. Navy; Chase A. Hughes, U.S. Navy; Matthew A. Humphreys, U.S. Navy; Adrian B. Korduba, U.S. Navy; Kari A. Neamand-Cheney, U.S. Navy; Nikki L. Pritchard, U.S. Navy; Alisha M. Smith, U.S. Navy; Jessica L. Whelpley, U.S. Navy; Sulola Adekoya, Virginia Department of Health; Victoria Alexander, Virginia Department of Health; Meredith Davis, Virginia Department of Health; Jonathan Falk, Virginia Department of Health; Katie Kurkjian, Virginia Department of Health; Elizabeth McCarty, Virginia Department of Health; James Moss, Virginia Department of Health; Angela Myrick-West, Virginia Department of Health; Chandni Patel, Virginia Department of Health; Rhonda Pruitt, Virginia Department of Health; Dawn Saady, Virginia Department of Health; Denise Sockwell, Virginia Department of Health; Amanda Touma, Virginia Department of Health; Stephanie Wheawill, Virginia Department of Health; Diane Woolard, Virginia Department of Health; Andrea Young, Virginia Department of Health; Latoya Griffin-Thomas, Virginia Division of Consolidated Laboratory Services; Sean Kelly, Virginia Division of Consolidated Laboratory Services; Jamie McLeod, Virginia Division of Consolidated Laboratory Services; Matthew C. Lambert, Wisconsin Department of Health Services; Tonya L. Danz, Wisconsin State Laboratory of Hygiene; Timothy Davis, Wisconsin State Laboratory of Hygiene; Kyley Guenther, Wisconsin State Laboratory of Hygiene; Erika Hanson, Wisconsin State Laboratory of Hygiene.