Preparedness for future pandemics: MERS vaccine candidate shows long-lasting immune response
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 persist for at least two years after a booster vaccination. MERS is listed by the World Health Organization as a priority pathogen (WHO R&D Blueprint for Epidemics) for which vaccines and therapies are urgently needed. 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) and was funded by DZIF and the Coalition for Epidemic Preparedness Innovations (CEPI). The findings were published recently in the journal Nature Communications.
The vaccine candidate investigated, MVA-MERS-S, is based on an attenuated poxvirus vector and presents the spike protein of the MERS coronavirus (MERS-CoV) to the immune system. MERS was identified in 2012 and causes severe respiratory disease with a high case fatality rate of up to 36 percent. The virus continues to circulate in animal reservoirs, such as dromedary camels. Although human infections remain rare, MERS-CoV is considered a potential threat for future outbreaks. New MERS cases have been reported in France and Saudi Arabia within the past two months. To date, no licensed vaccine against MERS exists, and there is no specific antiviral therapy.
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. The study was conducted within a consortium of the German Center for Infection Research (DZIF), which included the University Medical Center Hamburg-Eppendorf (UKE), the Institute of Virology at Charité – Universitätsmedizin Berlin, the Institute of Virology at Philipps University Marburg, and the Department of Viroscience at Erasmus Medical Center in Rotterdam in the Netherlands. The work was carried out in close cooperation with the Collaborative Research Center 1648 “Emerging Viruses: Structure, Pathogenesis and Immunity”.
Source: Press release of the University Medical Center Hamburg-Eppendorf (in German)
