A new vaccine platform could see us waving goodbye to boosters for some diseases, as one shot could cover every possible future strain of a virus. So far, it’s only been tested out in mice, but the scientists behind it are optimistic.

“This could be the universal vaccine that we have been looking for,” said Rong Hai, a virologist at the University of California, Riverside, in a statement. 

The vaccine uses a live, attenuated version of the virus. Lots of existing vaccines, like the MMR and chickenpox vaccines, use a similar method. Unlike those, however, the new vaccines will not rely on the body’s immune system mounting a response to the injected virus. Instead, they will activate a system called RNA interference, or RNAi.

It sounds a bit similar to the mRNA vaccines we've been using for COVID-19, but the way it works is quite different. 

“A host – a person, a mouse, anyone infected – will produce small interfering RNAs as an immune response to viral infection. These RNAi then knock down the virus,” explained lead author Shouwei Ding, distinguished professor of microbiology. 

Viruses are generally able to get around this response by producing proteins that block the RNAi, but weakening the virus first overcomes this problem. “It can replicate to some level, but then loses the battle to the host RNAi response. A virus weakened in this way can be used as a vaccine for boosting our RNAi immune system,” Ding said. 

And mutating won’t save them either. “Viruses may mutate in regions not targeted by traditional vaccines. However, we are targeting their whole genome with thousands of small RNAs,” Hai added. “They cannot escape this.”

It's worth noting that the idea that RNAi can form part of humans' defense against viral infection has caused controversy, but that hasn't stopped a number of researchers beginning investigations into RNAi-based therapeutics over the last decade or so.

The new vaccine platform also has one more big advantage. Because it doesn’t rely on a traditional immune response from B and T cells, it could potentially be used in very young babies, or those with immune disorders who are normally ineligible for live vaccines. 

To test this, the researchers created a vaccine against a mouse virus called Nodamura. They gave a single injection to mice that had been genetically modified to remove their B and T immune cells. That one shot was enough to protect them from infection with Nodamura virus for at least three months – quite a long time, when you consider a mouse’s typical lifespan of somewhere between two and three years.  

The vaccine worked even in newborn mice as they can already produce small RNAs, which is why it has potential for use in babies who would normally be too young to receive vaccines.

From their previous research, the team is convinced that flu infection also activates the RNAi system, so that’s going to be their next target. They plan to develop a nasal spray vaccine, to avoid some of the issues and fears associated with needles. 

“Our next step is to use this same concept to generate a flu vaccine, so infants can be protected. If we are successful, they’ll no longer have to depend on their mothers’ antibodies,” said Ding.

There's still some way to go, but if it is successful it's hoped that adapting the technology to cover other viruses would be relatively straightforward.

Ding explained, “There are several well-known human pathogens; dengue, SARS, COVID. They all have similar viral functions. This should be applicable to these viruses in an easy transfer of knowledge.”

The study is published in the Proceedings of the National Academy of Sciences.