A new type of vaccine – mRNA vaccines – were first seen in clinical practice as COVID-19 vaccines. These vaccines offer hope for much faster production of vaccines, even those for bacterial illnesses (remember, COVID-19 is caused by a virus).
Traditional vaccines include a dead or weakened (also called ‘attenuated’) sample of the bacteria that we want the immune system to learn to identify. To understand how an mRNA vaccine works, it is important to understand a little bit about how our immune system and diseases work.
Understanding mRNA vaccines for bacterial infections
- A bacterial disease is one that is caused by bacteria (single-celled ‘bugs’). Each bacterium (one cell) can divide to create two (which can each divide to create two more, etc). This allows them to reproduce very quickly (minutes rather than hours, in the laboratory).
- Each bacterial cell has various proteins on its surface. These proteins are what our immune system uses to identify the cells as belonging to something other than our own body. If this alerts our immune system to a threat, it will trigger an immune response. Some non-body cells are harmless, or even helpful (such as gut bacteria, which help us digest food).
- Bacterial cells, like all cells, use mRNA (messenger RNA) to produce those proteins.
If we work out the genetic code of the mRNA for a particular type of bacteria, we can create our own copy and put it into tiny (nano-sized) capsules that we inject into the bloodstream. The immune cells in the blood pick up these capsules and use the mRNA to create those bacterial surface proteins. The immune system then learns to recognise those proteins. This means that when the actual bacteria appears our bodies are primed to attack it.
It’s complicated, but it works. And the good news is that it could work for almost any bacteria, virus or fungus that has either DNA or RNA. It is even possible that they could be used to fight cancer (cancer cells often show certain surface proteins). They may also be effective for the treatment of diseases caused entirely or in part by a lack of effective protein production, such as cystic fibrosis.
COVID-19 as the launchpad for mRNA vaccines
The science to create such vaccines had been in the works for 30 years prior to the COVID-19 pandemic. All researchers needed was mRNA from an infectious disease to work with, and the time/money to do so. Scientists rapidly analysed the mRNA from the coronavirus that caused COVID-19. This allowed the scientists to create their own and start testing the vaccine within weeks of the start of the outbreak. It also means there could be much faster access to other (e.g., bacterial) vaccines in the future.
Can bacteria become resistant to an mRNA vaccine?
Technically, it’s possible for bacteria to start producing different proteins on their surface. However, if the changes are small enough it is likely that our immune system would still recognise the proteins. Our immune system can also learn and adapt, so this is more effective than using medicines to kill the bacteria.
What is the future of mRNA vaccines for bacterial infections?
Currently, many lab facilities are either closed due to the pandemic, or they have been repurposed to focus on COVID-19. Once the pandemic has ended, it is likely that attention will turn to using these vaccines for other diseases and conditions. Work has already begun on mRNA vaccines for Ebola, Zika and the flu, as well as melanoma (a type of skin cancer).
Read more about it:
- The Scientist “The promise of mRNA vaccines”
- Nature “The promise of mRNA vaccines: a biotech and industrial perspective”
- Harvard Health Blog “Why are mRNA vaccines so exciting?”
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