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Multiple diagnostic techniques identify previously vaccinated individuals with protective immunity against monkeypox
Erika Hammarlund1, Matthew W Lewis, Shirley V Carter
1Vaccine and Gene Therapy Institute, Oregon Health & Science University, 505 NW 185th Avenue, Beaverton, Oregon 97006, USA.
Nature Medicine
|August 9, 2005
Summary
Smallpox vaccination may offer decades of protection against monkeypox. This study found asymptomatic monkeypox infections in individuals vaccinated many years prior, suggesting lasting cross-immunity.
Area of Science:
- Virology
- Immunology
- Public Health
Background:
- Routine smallpox vaccination ceased in the US in 1972 for civilians and 1990 for military personnel.
- Long-term immunity following smallpox vaccination is debated, particularly regarding protection against orthopoxvirus diseases like monkeypox.
- Skepticism exists about the duration and efficacy of cross-protective immunity from smallpox vaccination against emergent orthopoxviruses.
Purpose of the Study:
- To investigate the persistence of immunity conferred by smallpox vaccination against monkeypox infection.
- To assess the extent of the 2003 US monkeypox outbreak by identifying asymptomatic cases in vaccinated individuals.
- To determine if cross-protective immunity against West African monkeypox is maintained for extended periods post-vaccination.
Main Methods:
- Utilized independent and internally validated diagnostic methods with high sensitivity (>95%) and specificity (>90%) for monkeypox detection.
- Identified and analyzed three previously unreported cases of monkeypox infection in individuals with a history of smallpox vaccination.
- Assessed the time elapsed since smallpox vaccination for the identified monkeypox cases (13, 29, and 48 years).
Main Results:
- Three asymptomatic cases of monkeypox were identified in individuals vaccinated against smallpox 13, 29, and 48 years prior.
- These individuals were unaware of their infection, indicating subclinical disease presentation.
- The findings suggest the 2003 US monkeypox outbreak was larger than previously estimated.
Conclusions:
- Cross-protective antiviral immunity against West African monkeypox can be maintained for decades after smallpox vaccination.
- Smallpox vaccination provides significant long-term protection, even against asymptomatic or subclinical orthopoxvirus infections.
- These findings have implications for understanding population immunity and potential strategies for managing future orthopoxvirus outbreaks.
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