How can vaccines be used to tackle AMR?
Vaccines are a way of protecting the body by preparing the immune system to fight diseases which can be caused by harmful microbes – known as pathogens.
Vaccines are often regarded as one of the greatest advancements in modern medicine. They save millions of lives worldwide every year [1], are responsible for the eradication of smallpox [2] and Rinderpest, the deadliest cattle disease in history [3], and were a crucial part of efforts to control COVID-19.
How do vaccines work?
To understand how vaccines work, we need to start with a quick look at the immune system. The immune system is responsible for protecting the body from foreign substances like pathogens.
The immune system responds to pathogens in many different ways: one of them is the production of antibodies. Antibodies are specific to the markers found on the pathogen (which are called antigens). Antibodies bind to the antigens which helps the immune system to target the pathogen. Our bodies are capable of producing thousands of different antibodies. Once a pathogen enters the body, the immune system works to ‘remember’ the specific antibody for that pathogen if it’s seen it before or develop the right antibody to target the new pathogen.
To create a new type of antibody takes time and while this is happening, the host is susceptible to attack by the pathogen. There is a chance that the pathogen could cause life threatening damage or become too much for the immune system to handle.
But, once the specific antibody is created, specialist immune cells can create more of them rapidly. Antibodies can neutralise pathogens by binding to their surface, preventing them from infecting cells. They can also clump the pathogens together, making them an easier target for other specialist immune cells.
To prepare for a faster response in the future, the immune system also produces specialist memory cells. These cells remember the specific antigens of the pathogen and how to produce the right antibodies. If the body is exposed to the same pathogen again, the right antibodies can be produced much faster for a more effective response, protecting the host from becoming seriously ill or dying. If the immune system can effectively respond to the pathogen the individual is considered immune.
Vaccines are a way of artificially stimulating this natural immune response. Most vaccines work by introducing a small amount of a weakened or inactive pathogen (or even just a part of it) into the body. Without encountering, or feeling the full effects of the pathogen, recipients of an effective vaccine will have an immune system that is better equipped to respond, produce the right antibodies quickly and protect the body. This prevents the recipient of the vaccine from getting seriously ill or dying if they encounter the pathogen in the future.
How can vaccines be useful against AMR?
Vaccines and effective vaccine programmes can be useful against AMR in a number of ways:
- If a large proportion of the population are vaccinated against disease, they’re less likely to get sick. If fewer people are getting sick from a disease, fewer antimicrobials will be needed. This also reduces the risk of incorrect use of antimicrobials, for example taking antibiotics against a viral infection. If fewer antimicrobials are administered, the chances of pathogens developing resistance is reduced.
- Some pathogens have already developed resistance to most available antimicrobials. Developing vaccines against these pathogens is vital. Any reduction in the use of the remaining antimicrobials will slow the rate at which further resistance will develop, therefore extending the lifetime of these precious resources.
- If sufficient levels of immunity are maintained, an infected individual is less likely to spread the disease to other members of the population, whether they’re vaccinated or not (a concept called herd immunity).
Why don’t we have vaccines for everything?
There are some barriers in the way of making vaccines. Pathogens also have clever ways of evading the immune system, making it difficult to create vaccines. Many pathogens, for example, evolve rapidly, and their antigens change with them, which means that the antigens that the immune system was trained on (from a vaccine or from previous infection) become quickly out of date.
Developing vaccines is complicated and often requires international collaboration. Production of the vaccine against the parasite responsible for malaria, for example, took 30 years. But, as we have seen with the production of the COVID-19 vaccines, new technologies, better financing and careful preparation can speed up these processes.
There are also practicalities to consider. Vaccinating everyone isn’t always possible or cost effective. It’s often cheaper to distribute antimicrobials than prevent infection with vaccines. It is hard, for example, to vaccinate wild animal populations where we can vaccinate companion animals and livestock.
While making new vaccines is difficult, even the vaccines we do have aren’t always being distributed to the right places. Lower-Middle income countries, especially, often aren’t getting access to the right vaccines.
What needs to be done to utilise vaccines to tackle AMR?
There is work to be done to get to a position where vaccines are being developed and used effectively against AMR.
What the community can do right now, is to increase access and uptake of vaccines we do have, incentivise the development of AMR-relevant vaccines and gather more data on the impact of vaccines on AMR so that we can be best placed to target research and response.
Vaccines have an important role to play in tackling AMR, but they are one part of a complex picture. A coordinated, collaborative approach utilising all available strategies must be embraced.
Useful Resources
British Society for Immunology
[1] https://www.who.int/health-topics/vaccines-and-immunization#tab=tab_1
[2] https://www.who.int/news-room/spotlight/history-of-vaccination/a-brief-history-of-vaccination
[3] https://www.woah.org/en/article/ten-years-on-rinderpest-eradication-highlights-the-value-of-vaccines/