New single-dose vaccine gives ‘strong rabies protection’

A new single-dose vaccine developed by the University of Oxford provides protection against rabies above the World Health Organisation threshold within two months, a study has shown.

Researchers aimed to look at safety and measure immune responses from the vaccine by analysing levels of rabies-neutralising antibodies.

The university tested the ChAdOx2 RabG vaccine on 12 people, in the rabies inoculation's first human tests.

Of the 12 volunteers, three received a low dose, three a medium dose and six a high dose of the vaccine.

Strong immune responses against rabies were generated by the vaccine.

All volunteers who received a medium or high dose developed levels of rabies-neutralising antibodies above the World Health Organisation protective threshold within two months.

No serious adverse effects or safety concerns were reported by the volunteers, with typical short-lived vaccine side-effects such as soreness at the injection area or feverishness mainly reported by the groups who had received the medium and higher doses.

The researchers also assessed the longer term immune response to the vaccine.

They found that six of the seven middle and high-dose recipients who returned for another follow-up a year after vaccination maintained neutralising antibody levels above the protective threshold.

This showed that the immune response from the vaccine remained over time.

“We’re absolutely delighted with these early results,” said associate professor Sandy Douglas, head of the trial at Oxford's Jenner Institute.

"The vaccine has performed even better than we had expected. The problems with existing rabies vaccines are that they are expensive and require multiple doses.

“We’re very hopeful that expanded trials in countries affected by rabies will prove that this new vaccine could enable routine, affordable, single-dose vaccination against this devastating disease.”

Researchers hope the results will support further development of the vaccine and allow larger clinical trials to take place.

A clinical trial to assess safety and immunogenicity in Tanzania is also continuing and results of that trial are expected this year, with full results due in late 2023.

"New rabies vaccines based on modern vaccine technologies could become important tools in preventing the tens of thousands of rabies deaths that occur annually,” said Dr Daniel Jenkin, lead research fellow in the trial at the Jenner Institute.

"Our strong early clinical trial data with ChAdOx2 RabG supports further development of this approach.

“The ChAdOx2 RabG vaccine is based on the ChAdOx2 vector, a weakened version of a common cold virus [adenovirus] that has been genetically modified so that it is impossible for it to replicate in humans, and is similar to the technology used successfully in the Oxford-AstraZeneca Covid-19 vaccine."