Are vaccines an effective tool to prevent disease?

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

Yes, vaccines are widely regarded by major health organizations and decades of evidence as one of the most effective tools to prevent disease.

Evidence for Effectiveness

> Vaccination is one of the most effective ways to prevent diseases.

> Vaccines are among the most powerful inventions in history, making once-feared diseases preventable

Key evidence includes:

1. Millions of lives saved:

Of the vaccines included in the 50-year study, the measles vaccination had the most significant impact on reducing infant mortality, accounting for 60% of the lives saved due to immunization.

2. Eradication and elimination of diseases:

> Vaccines helped eradicate smallpox in 1977 and are on their way to eradicating polio and eliminating neonatal tetanus and measles.

Vaccines have also resulted in the eradication of two major pathogens, rinderpest and smallpox, as well as the local elimination of others, such as measles.

A classic example is the 96% decrease in the incidence of polio that occurred within 7 years of the introduction of the Salk and Sabin polio vaccines.

As the result of vaccination against polio more than 20 million people are able to walk today who would otherwise have been paralysed.

Vaccination directly contributed to reducing infant deaths by 40% globally, and by more than 50% in the African Region over 50 years for 14 diseases including diphtheria, pertussis, tuberculosis, yellow fever and others.

3. Large-scale U.S. data:

Among children born during 1994–2023, routine childhood vaccinations will have prevented approximately 508 million cases of illness, 32 million hospitalizations, and 1,129,000 deaths.

More specifically, among approximately 117 million children born during 1994–2023, routine childhood immunization was estimated to prevent 508 million lifetime cases of illness and 32 million hospitalizations.

For seasonal diseases, during the 2024–25 influenza season, influenza vaccination prevented an estimated 5 million medical visits, 180,000 hospitalizations, and 12,000 deaths caused by influenza viruses.

For COVID-19, the 2024-25 COVID-19 vaccine was an estimated 40% effective against hospital admission and 79% effective against invasive mechanical ventilation (IMV) or death.

How Vaccines Prevent Disease

Vaccines work by introducing a weakened or inactive form of the virus or bacteria into the body, triggering an immune response without causing illness. They are described as one of the most effective tools we have in preventing diseases, because they train the immune system to recognize and fight pathogens.

They also provide community protection through herd immunity:

> Vaccines protect the recipient and the people in close contact with him or her. ... This is known as herd immunity.

Herd immunity happens when enough people in a community are immune to a disease that they "shield" those who don't have immunity. The more contagious the disease is, the larger the population vaccination rate needs to be.

Limitations and Considerations

> A person is far more likely to be seriously harmed by a disease than by a vaccine.

Vaccine-preventable diseases like measles, meningitis, hepatitis B or polio can be deadly or cause severe illness and disability.

Overall, the consensus from WHO, CDC, and peer-reviewed literature is that vaccines are highly effective, cost-effective, and life-saving, and have been the cornerstone for controlling, eliminating, and eradicating infectious diseases.