Maintenance of Measles Elimination Status in the United States for 20 Years Despite Increasing Challenges.
MMR vaccine
measles
measles outbreak
Journal
Clinical infectious diseases : an official publication of the Infectious Diseases Society of America
ISSN: 1537-6591
Titre abrégé: Clin Infect Dis
Pays: United States
ID NLM: 9203213
Informations de publication
Date de publication:
31 08 2022
31 08 2022
Historique:
received:
31
08
2021
pubmed:
2
12
2021
medline:
3
9
2022
entrez:
1
12
2021
Statut:
ppublish
Résumé
Measles elimination (interruption of endemic measles virus transmission) in the United States was declared in 2000; however, the number of cases and outbreaks have increased in recent years. We characterized the epidemiology of measles outbreaks and measles transmission patterns after elimination to identify potential gaps in the US measles control program. We analyzed national measles notification data from 1 January 2001 to 31 December 2019. We defined measles infection clusters as single cases (isolated cases not linked to additional cases), 2-case clusters, or outbreaks with ≥3 linked cases. We calculated the effective reproduction number (R) to assess changes in transmissibility and reviewed molecular epidemiology data. During 2001-2019, a total of 3873 measles cases, including 747 international importations, were reported in the United States; 29% of importations were associated with outbreaks. Among 871 clusters, 69% were single cases and 72% had no spread. Larger and longer clusters were reported since 2013, including 7 outbreaks with >50 cases lasting >2 months, 5 of which occurred in known underimmunized, close-knit communities. No measles lineage circulated in a single transmission chain for >12 months. Higher estimates of R were noted in recent years, although R remained below the epidemic threshold of 1. Current epidemiology continues to support the interruption of endemic measles virus transmission in the United States. However, larger and longer outbreaks in recent postelimination years and emerging trends of increased transmission in underimmunized communities emphasize the need for targeted approaches to close existing immunity gaps and maintain measles elimination.
Sections du résumé
BACKGROUND
Measles elimination (interruption of endemic measles virus transmission) in the United States was declared in 2000; however, the number of cases and outbreaks have increased in recent years. We characterized the epidemiology of measles outbreaks and measles transmission patterns after elimination to identify potential gaps in the US measles control program.
METHODS
We analyzed national measles notification data from 1 January 2001 to 31 December 2019. We defined measles infection clusters as single cases (isolated cases not linked to additional cases), 2-case clusters, or outbreaks with ≥3 linked cases. We calculated the effective reproduction number (R) to assess changes in transmissibility and reviewed molecular epidemiology data.
RESULTS
During 2001-2019, a total of 3873 measles cases, including 747 international importations, were reported in the United States; 29% of importations were associated with outbreaks. Among 871 clusters, 69% were single cases and 72% had no spread. Larger and longer clusters were reported since 2013, including 7 outbreaks with >50 cases lasting >2 months, 5 of which occurred in known underimmunized, close-knit communities. No measles lineage circulated in a single transmission chain for >12 months. Higher estimates of R were noted in recent years, although R remained below the epidemic threshold of 1.
CONCLUSIONS
Current epidemiology continues to support the interruption of endemic measles virus transmission in the United States. However, larger and longer outbreaks in recent postelimination years and emerging trends of increased transmission in underimmunized communities emphasize the need for targeted approaches to close existing immunity gaps and maintain measles elimination.
Identifiants
pubmed: 34849648
pii: 6443449
doi: 10.1093/cid/ciab979
doi:
Substances chimiques
Measles Vaccine
0
Types de publication
Journal Article
Langues
eng
Sous-ensembles de citation
IM
Pagination
416-424Informations de copyright
Published by Oxford University Press for the Infectious Diseases Society of America 2021.
Déclaration de conflit d'intérêts
Potential conflicts of interest. The authors: No reported conflicts of interest. All authors have submitted the ICMJE Form for Disclosure of Potential Conflicts of Interest.