A new study has shown for the first time that an experimental vaccine against Middle East Respiratory Syndrome (MERS) induces a stable and functional immune response in humans that persists for at least two years after a booster vaccination. The results mark an important step toward an effective MERS vaccine and strengthen the scientific basis for pandemic preparedness.
The long-term clinical study was conducted by an international research team from the German Center for Infection Research (DZIF). The findings were published in the journal Nature Communications.
The vaccine candidate MVA-MERS-S under investigation is based on an attenuated poxvirus vector that presents the spike protein of the Middle East Respiratory Syndrome (MERS) Coronavirus (MERS-CoV) to the immune system.
First identified in 2012, MERS causes severe respiratory disease with a case fatality rate of up to 36%. The virus continues to circulate in animal reservoirs, including dromedary camels. Though human infections are rare, MERS-CoV poses a potential threat of future outbreaks. New MERS cases have been reported in France and Saudi Arabia within the past two months.
The World Health Organization (WHO) lists the virus as a priority pathogen (WHO R&D Blueprint for Epidemics) for which vaccines and therapies are urgently needed. Currently, however, there is no licensed vaccine or specific antiviral therapy against MERS.
Additional booster shot significantly improves long-term immune response
In a Phase I clinical trial, healthy adults in Hamburg and Rotterdam received three vaccinations with MVA-MERS-S. For the long-term follow-up now published, the research team examined how well the immune system of 48 participants from Hamburg remained prepared to respond to the virus 24 months after the third vaccination.
The analysis showed that both MERS-CoV-specific antibodies and specialized immune cells were still present at this timepoint. Notably, antibody levels remained stable at levels that were comparable to the highest levels measured after the second vaccination. In addition, the antibodies were able to neutralize clinically relevant, circulating variants of the MERS coronavirus.
In this context, a long-lasting immune response indicates that the body can still recognize the virus long after vaccination and mount a rapid response upon exposure. The study demonstrates that such durable immunity can be achieved in particular through the administration of a targeted booster vaccination.
“That we were able to measure such a stable immune response two years after the last vaccination was by no means a given,” says first author Dr. Leonie Mayer from the Institute for Infection Research and Vaccine Development (IIRVD) at the University Medical Center Hamburg-Eppendorf (UKE). “Our results show that an additional booster vaccination significantly improves long-term immunity.”
Long-term data show lasting immune response for the first time
To date, the absence of a licensed MERS vaccine is largely due to the rarity and unpredictability of the disease, which makes conducting large-scale efficacy trials difficult.
This underscores the importance of detailed immunological analyses in early-phase clinical trials to gain first insights into vaccine performance. The long-term data now available close a key knowledge gap by demonstrating, for the first time, how durable vaccine-induced immunity against MERS can be.
“This study represents another important step in global preparedness for emerging viruses,” says Prof. Dr. Marylyn Addo, scientific lead of the study and director of the IIRVD.
“It shows that we can develop vaccines that not only have short-term effects but also elicit long-lasting immune responses. This knowledge is crucial for containing future outbreaks at an early stage, particularly in high-risk populations, and for better protecting society,” adds Addo, who has been Vice Chair of the DZIF Executive Board since the beginning of 2026 and co-coordinates the DZIF Bridging Topic Vaccines.
The findings provide an important foundation for further clinical trials and for the strategic development of vaccines against MERS and other emerging viruses.
Publication details
Leonie Mayer et al, Two-year persistence of MERS-CoV-specific antibody and T cell responses after MVA-MERS-S vaccination in healthy adults, Nature Communications (2026). DOI: 10.1038/s41467-025-68248-5
Journal information:
Nature Communications
Key medical concepts
Middle East Respiratory Syndrome Coronavirusneutralizing antibody
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