Vaccines protect us from serious diseases and some can also help contain the spread of disease, saving around 2-3 million lives every year. Many of us receive these vaccines, for diseases such as measles, meningitis and pneumonia, as routine childhood immunisations. This has led to these diseases becoming less common, or even eliminated, in areas with high levels of vaccination. Some diseases have the potential to be eradicated, as smallpox was in 1980. But because most can exist in animals or in the environment (for example in the soil), they pose an ever-present threat, which is why it is so important that vaccination coverage remain high. Whenever vaccination levels drop, either because of hesitancy or when services are disrupted, these deadly diseases can quickly rebound. The life-saving power of vaccination is a major reason why global health organisations like Gavi are working hard to get vaccines out to low-resource areas where vaccines are either unaffordable or inaccessible. Even in countries where the risk of infectious disease is low, getting vaccinated is still important in order to protect vulnerable people who can’t be vaccinated, such as people with compromised immune systems (like those with cancer or HIV/AIDS) or people with extreme allergies. In addition, vaccines are not always as effective in triggering a robust immune response in elderly people, who may be more vulnerable to disease, and so widespread immunisation is critical to protecting them.