An international research team has designed a vaccine shown to be effective in protecting dromedaries against the coronavirus (CoV) that causes MERS. According to News Medical, the vaccine may reduce animal-to-animal and animal-to-human infections by significantly reducing nasal excretion of the virus, and could be also tested for the protection of persons at greater risk of infection by the virus. For the study, the researchers used eight dromedaries (four vaccinated and four unvaccinated) to test the protective efficacy of MVA-S, which is a modified vaccine based on the orthopoxvirus virus Vaccinia Virus Ankara that expresses the MERS-CoV spike (S) protein.

The study was conducted with eight dromedaries from the Canary Islands. The animals were studied over 10 weeks in the same unit: one week of acclimatization, two separate vaccinations over four weeks, inoculation with MERS-CoV three weeks after the first vaccination, then two weeks of post-infection clinical monitoring and finally the necropsy of the animals.

The results of the study show that the vaccine is able to protect the animals at the level of the upper respiratory tract. When compared to the unvaccinated dromedaries, those that were vaccinated and subsequently infected with MERS-CoV showed a notable reduction in viruses excreted from the respiratory tract. In addition, the News Medical report notes that the protection was also demonstrated by the presence of antibodies that were able to neutralize the virus, by preventing its replication, in the serum of the vaccinated animals and in their nasal cavities.

The study revealed that none of the vaccinated animals developed clinical signs associated with infection on being inoculated with the virus, while only the control animals developed cold-like signs, such as increased nasal mucus secretion. The results of the research indicated that vaccination with MVA-S would serve mainly to reduce excretion of the virus and therefore its propagation, as indicated in the News Medical report.

The international research team believes that vaccinating the youngest dromedaries could drastically reduce excretion of the virus since they excrete larger quantities of MERS-CoV than adults, which suggests they should be vaccinated first. The researchers also noted that the vaccine based on MVA-S might also be tested on persons at higher risk of being infected by the virus, such as hospital workers. However, further studies are needed to determine the duration of the protection afforded by the vaccine because mucus immunity is typically a short-term effect.

Joaquim Segalés states, “It could be that total protection against MERS-coronavirus will never be attained. This is nonetheless a very significant step forward in the fight against this pathogen; now we need to delve more deeply into the duration of the immunity and dosage before applying it in real situations.”

Source: News Medical