SINGLE-DOSE mRNA vaccines fully protected hamsters against Andes hantavirus, supporting faster outbreak-response vaccine development efforts.
Andes Hantavirus Vaccine Shows Complete Protection
Two investigational mRNA vaccines against Andes hantavirus provided complete protection in a lethal animal challenge model after just one intramuscular dose, according to newly published findings.
The vaccines were tested in female golden Syrian hamsters, the only animal model that closely recapitulates fatal hantavirus pulmonary syndrome caused by Andes virus in humans. Animals received either a 1-methylpseudouridine-modified or non-modified mRNA vaccine encoding the Andes virus envelope glycoproteins Gn and Gc, at doses of 25 μg, 5 μg, or 1 μg. Four weeks later, they were challenged with 350 plaque-forming units of Andes virus and monitored for weight loss and clinical disease.
All vaccinated hamsters were protected from overt disease, including those given the lowest tested dose. No replicating virus was detected in liver tissue at study termination on day 28 after infection. In contrast, four of five control hamsters reached endpoint by days 9 to 10 after infection, including two deaths and two humane euthanasia events. The surviving control animal experienced progressive weight loss without recovery to baseline.
Fast Immune Response Could Support Outbreak Control
The Andes hantavirus vaccine candidates also generated early, dose-dependent IgG responses. Both vaccine platforms elicited antibodies by day 14 after vaccination, with significantly higher titers at 25 μg than at 1 μg. Immunogenicity was equivalent between the modified and non-modified mRNA vaccines at each dose level.
The results are clinically relevant because Andes virus differs from many other hantaviruses in its ability to spread person to person through close contact with respiratory secretions. The May 2026 outbreak aboard the MV Hondius cruise ship, which departed from Argentina, resulted in 13 reported cases and three deaths. Nearly 150 passengers and high-risk contacts dispersed across 23 countries, creating a complex contact-tracing challenge during a 42-day incubation window.
Clinical Translation Remains the Next Step
No Andes hantavirus vaccines or preventive treatments are currently approved by the U.S. Food and Drug Administration or European Medicines Agency. The single-dose protection, dose-sparing efficacy, and antibody responses within 2 weeks support accelerated development toward clinical trials.
Researchers noted that viral load was assessed only in the liver, so circulating virus or lung infection could not be excluded. However, liver titers correlate with lung titers in this hamster model, supporting their use as a vaccine efficacy measure. Further studies will need to define the optimal vaccine modality, minimal effective dose, scalability, and potential role in post-exposure prophylaxis for high-risk contacts during outbreaks.
Reference
Meyer M et al. Single-dose mRNA vaccines against Andes hantavirus. The Lancet. 2026;DOI: 10.1016/S0140-6736(26)01124-4.
The University of Texas Medical Branch. UTMB scientists track breakthrough single-dose vaccines for Andes hantavirus strain. 2026. Available at: https://www.utmb.edu/news/article/utmb-news/2026/06/11/utmb-scientists-track-breakthrough-single-dose-vaccines-for-andes-hantavirus-strain. Last accessed: 15 June 2026.
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