I'll gather the latest evidence on how well vaccines prevent disease.
Yes, vaccines are widely recognized by global health authorities and scientific evidence as a highly effective tool to prevent disease.
Mechanism
•Vaccines work by imitating an infection to engage the body's natural defenses.
•Vaccines contain weakened or inactive parts of a particular organism (antigen) that triggers an immune response within the body. Newer vaccines contain the blueprint for producing antigens rather than the antigen itself
•Vaccines train your immune system to create antibodies, just as it does when it's exposed to a disease. However, because vaccines contain only killed or weakened forms of germs like viruses or bacteria, they do not cause the disease or put you at risk of its complications.
•If the person is exposed to the dangerous pathogen in the future, their immune system will be able to respond immediately, protecting against disease
Effectiveness
•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 (1).
•Immunization is a global health success story, saving millions of lives every year.
•Immunization currently prevents 3.5 million to 5 million deaths every year from diseases like diphtheria, tetanus, pertussis (whooping cough), influenza and measles.
•We now have vaccines to prevent more than 30 life-threatening diseases and infections, helping people of all ages live longer, healthier lives.
•Vaccines protect against many different diseases, including cervical cancer, cholera, COVID-19, diphtheria, hepatitis B, influenza, measles, polio, rabies and others.
•Vaccines are the most effective tool to prevent the outbreak of many dangerous diseases, including polio and measles.
•Vaccines are among the most cost-effective ways to protect against infectious diseases.
Historical Evidence
•Smallpox was eradicated worldwide in 1980.
•Over the past half century, in addition to eradicating smallpox, vaccines are estimated to have averted 154 million deaths and saved 9 billion years of life.
•The introduction of a vaccine has, in many cases, led to a very large decrease in the incidence of the targeted disease — such as the 96% decrease in the incidence of polio that occurred within 7 years of the introduction of the Salk and Sabin polio vaccines
•In 2013, it was estimated that 103 million cases of childhood diseases in the United States had been prevented by the use of vaccines since 1924.
•Vaccines prevented more than 500 million illnesses and 1.13 million deaths among children born over the last three decades, according to a new study.
•Routinely administered vaccines are estimated to prevent 3.5 to 5 million deaths annually across 20 life-threatening vaccine-preventable diseases (VPDs)
Nuance on Effectiveness
Effectiveness does not always mean absolute prevention of infection. For example, effectiveness for COVID-19 vaccines in current reporting is not absolute prevention of infection but measurable reduction in severe outcomes—many studies and public-health analyses emphasize strong protection, especially against hospitalization and critical illness in older adults
Overall, consensus from the World Health Organization, CDC, and peer-reviewed research is that vaccines are safe, cost-effective, and one of the most consistently effective interventions against infectious diseases such as smallpox, rabies, polio, and various childhood illnesses.