Why do we use vaccines and how well do they work?
The goal of vaccination programmes is to protect and improve the health of the entire population through disease prevention. Vaccines are estimated to prevent between 3.5 and 5 million deaths worldwide every year. The Smallpox vaccine was so successful that nobody has had the disease globally since 1978. Vaccines also serve wider purposes in public health as they prevent us passing infections from one person to another, help control disease outbreaks that can overwhelm health services and help protect the most vulnerable in society who can sometimes not get a vaccine themselves. The effectiveness of individual vaccines can vary depending on different factors, including the disease being targeted, the population being vaccinated and the type of vaccine.
Vaccines have saved the lives of an estimated 101 million infants globally over the past 50 years. Smallpox used to kill 30% of the people it infected. In high-income regions of the world, such as Western Europe, measles still causes death in about 1 in 5000 cases. But in the poorest regions, as many as 1 in 100 will die. 99% of people who receive two doses of the MMR vaccine will be protected against measles.
Polio mainly affects children under the age of five, with one in every 200 infections leading to irreversible paralysis while 5-10% of those infected die. Thanks to vaccination, the last case of naturally occurring polio in the UK was in 1984. You can find out more about the effects of polio on the people who catch it in this video: . The human papillomavirus (HPV) vaccine, introduced in the UK in 2008, has been calculated to reduce the risk of cervical cancer death before age 30 to effectively zero, with no woman in their early 20s dying from cervical cancer in England between 2020 and 2024.
There are several overlapping reasons why health authorities offer vaccination to people.
Protecting individuals
First, they protect you against serious illness from infections. Despite great advances in medicine and treatments for infectious diseases, there are still some that cannot be effectively cured because no treatment exists or it is not fully effective. This is particularly true for many diseases caused by viruses but also for some bacterial infections and in some cases made even more serious by the spread of antibiotic resistance. Vaccines do not always prevent infectious viruses and bacteria from getting into your body in the first place. They help prepare your immune system to fight off the disease when it attacks and may block it completely or reduce the severity of the illness it causes. Not everyone's immune system works the same and although some people may get ill despite having the vaccine, the illness is usually milder than in an unvaccinated person. (Find out more in What are vaccines and how do they work?)
You can read more about some of the science behind why we know vaccines work here:
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Protecting the vulnerable
Another reason for using vaccines is to protect vulnerable people who are more prone to the severe symptoms of an infectious disease or are unable to have a vaccine themselves. If those around them are vaccinated, they may be less likely to catch or to pass on the disease.
Protecting public health
Vaccinations are also critical for preventing and controlling infectious disease outbreaks. Without vaccination, outbreaks of diseases such as flu or COVID-19 can quickly overwhelm health services and hospitals. By reducing the severity of the disease, preventing deaths and reducing the spread of the disease, vaccinations are vital for protecting public health. The UK government estimates that in England alone, close to 230,000 hospitalisations are prevented each year by the pre-school vaccination programme alone.
Eradicating diseases
With a concerted, global, vaccination effort, it is even possible to completely eradicate a disease from naturally passing between people. This has been managed in humans for smallpox, which took 20 years, and for type 2 and 3 polio viruses. The UK was declared polio-free in 2003, but polio still persists in other parts of the world where vaccination programmes have been less successful.