Are vaccines an effective tool to prevent disease?

I'll gather the latest evidence on how well vaccines prevent disease.

Yes, vaccines are one of the most effective tools to prevent disease. Evidence from laboratory science, clinical trials and real-world monitoring consistently shows they prevent infection, severe disease, hospitalization and death.

How vaccines work

> Vaccination is a simple, safe, and effective way of protecting you against harmful diseases, before you come into contact with them

Vaccines train the immune system to create antibodies without causing disease. Once exposed to one or more doses, we typically remain protected for years, decades or even a lifetime - This is what makes vaccines so effective.

> Without vaccines, we are at risk of serious illness and disability from diseases like measles, meningitis, pneumonia, tetanus and polio

Two key reasons to get vaccinated are to protect ourselves and to protect those around us who cannot be vaccinated.

Effectiveness measured in trials and real world

Large reviews confirm both:

> Vaccines cannot always prevent infection, but they can substantially reduce the risk of serious disease

Population-level impact

> Vaccination is one of the most effective ways to prevent diseases. Over the past 50 years, essential vaccines against just 14 diseases have saved at least 154 million lives

Other estimates:

We now have vaccines to prevent more than 30 life-threatening diseases, including cervical cancer, cholera, COVID-19, diphtheria, hepatitis B, influenza, measles, polio and others listed by WHO.

Vaccines are also critical to the prevention and control of infectious disease outbreaks.

Eradication and near-eradication examples

> Smallpox was eradicated through global vaccination and surveillance programs. Worldwide cases of polio caused by wild poliovirus have fallen by more than 99% since 1988

This illustrates herd immunity - when sufficient percentage of a population is immunized, circulation is limited, protecting even those who cannot be vaccinated.

Limitations

No vaccine is 100% effective for every person, and effectiveness can vary by age, health status, pathogen variant, and time since vaccination. High coverage is needed to maintain herd immunity, and delays in vaccination increase risk of serious illness.

However, WHO and national regulatory authorities continuously monitor safety and effectiveness after approval, and research confirms the risk-benefit ratio is overwhelmingly favorable: serious side effects are extremely rare, while vaccine-preventable diseases can cause blindness, deafness, paralysis, brain damage, cancer and death.

Conclusion: Based on 50 years of data, controlled trials and real-world surveillance, vaccination is a safe, effective and life-saving tool that prevents millions of deaths and disabilities annually and remains the best health investment for preventing infectious diseases.