The MV Hondius outbreak has brought a recurring question back to the fore : why, when vaccines were developed in record time against COVID-19, is there still no vaccine against Andes hantavirus ? The answer has less to do with science than with a hard-to-solve epidemiological and economic equation.
No licensed vaccine against the Andes virus
Let us be clear from the outset : to date, no vaccine is licensed against the Andes virus, nor more broadly against hantavirus pulmonary syndrome (HPS), whether in the United States, Europe or Latin America.
This absence may surprise, because hantavirus vaccines do exist… but elsewhere, and against other viruses. In South Korea, the inactivated Hantavax vaccine has been used for decades. In China, inactivated vaccines (rodent-brain-derived and, more recently, cell-culture-derived) are administered on a large scale. But these vaccines target the Hantaan and Seoul viruses, responsible in Asia and Europe for haemorrhagic fever with renal syndrome (HFRS) — a disease distinct from American HPS. They do not protect against the Andes virus.
A DNA candidate that proved itself… in phase 1
Research is not at a standstill, however. The most advanced candidate against the Andes virus is a DNA vaccine developed by USAMRIID, the US Army's medical research institute of infectious diseases (Fort Detrick, Maryland).
Its principle : have the body produce the virus's two envelope glycoproteins (Gn and Gc), training the immune system to recognise them. The phase 1 study, published in 2024, delivered encouraging results :
- 48 healthy adults, split into four cohorts (2 or 4 mg doses, 3- or 4-injection schedules) ;
- needle-free administration, by pressure injection (PharmaJet Stratis system) ;
- 88 to 90% of participants in the best-dosed cohorts developed neutralising antibodies (67% in the lowest-dose cohort) ;
- the authors' conclusion : a "safe" vaccine inducing a "robust and durable" immune response.
It is a real milestone — but a phase 1 only measures safety and immune response, not actual efficacy in preventing disease. And that is exactly where the road stalls.
The real obstacle: not enough patients to prove it works
To license a vaccine, you need a phase 3 : demonstrating, across a large population, that the vaccinated fall significantly less ill than the unvaccinated. But HPS is a rare, sporadic disease. The Andes virus causes a few hundred cases a year, scattered across vast rural areas of South America.
As a result, to observe enough cases and prove efficacy, you would need to enrol tens of thousands of people in at-risk regions — typically Patagonia — and follow them for years. Such a trial is logistically heavy and very costly, for a narrow commercial market. That was the analysis summed up by Der Spiegel on 18 May 2026 under a telling headline : how lack of money and lack of patients are slowing development.
In other words : it is not that science cannot make a vaccine — it is that proving it works is very hard, for want of enough patients to protect.
What the MV Hondius episode could change
A high-profile outbreak like the MV Hondius can reshuffle the deck by reviving scientific interest and funding. Several avenues remain open : optimising the DNA candidate, nucleic-acid platforms (including messenger RNA) being explored against hantaviruses, and work carried out notably in Argentina, where hospital teams have for years been seeking a vaccine suited to South American strains (France Info, 21 May 2026).
But perspective is in order : no licensed product is expected in the short term. For now, prevention rests on what already works — avoiding exposure to reservoir rodents and their droppings, and applying strict protocols in case of contamination.
What about treatment?
The picture is similar on the therapeutic side : there is no licensed specific antiviral against HPS. Care remains supportive — respiratory support and, in severe forms, ECMO (extracorporeal membrane oxygenation), as for the French patient hospitalised at Bichat. Hence the importance of early diagnosis and of monitoring exposed people throughout the incubation period.
Key takeaways
- No licensed vaccine against Andes hantavirus / HPS, in the Americas or Europe.
- Existing vaccines (Hantavax in Korea, inactivated vaccines in China) target other strains (Asian HFRS), not the Andes virus.
- A USAMRIID DNA candidate cleared phase 1 (88-90% neutralising-antibody responders, safety confirmed).
- The bottleneck is logistical and economic: the disease is too rare for a realistic phase 3 efficacy trial.
- No vaccine expected in the short term; prevention rests on rodent avoidance and PPE/disinfection protocols.
For the disease and its management, see Andes virus in depth. On decontamination after exposure, read why you wet surfaces instead of sweeping.