Are vaccines an effective tool to prevent disease?

Vaccines are one of medicine's most proven defenses — I'll gather the latest evidence on their effectiveness.

Yes, vaccines are considered one of the most effective tools to prevent disease by major public health organizations worldwide.

Evidence for 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). During the same period, vaccination has contributed to 40% of the drop in infant deaths.

> Immunization is a global health success story, saving millions of lives every year.

Current global estimates include:

•Immunization currently prevents 3.5 million to 5 million deaths every year from diseases like diphtheria, tetanus, pertussis, influenza and measles.

•WHO estimates that today immunizations prevent between 2 and 3 million deaths annually and protect many more people from illness and disability.

•Vaccination is one of the most effective interventions against infectious diseases and is estimated to prevent 2-3 million deaths annually, with an additional 1.5 million deaths that could be averted with improvements in global vaccination coverage.

Vaccination is considered the most successful and cost-effective medical intervention ever.

How Vaccines Prevent Disease

Vaccines reduce risks of getting a disease by working with your body’s natural defenses to build protection. When you get a vaccine, your immune system responds.

> 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.

We now have vaccines to prevent more than 30 life-threatening diseases and infections, including cervical cancer, cholera, COVID-19, diphtheria, hepatitis B, influenza, measles, meningitis, mumps, pertussis, pneumonia, polio, rabies, rubella, tetanus, typhoid, varicella and yellow fever.

Historical and Real-World Impact

•The only human disease ever eradicated, smallpox, was eradicated using a vaccine, and a second, polio, is near eradication, also using 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.

•A greater than 92% decline in cases and a 99% or greater decline in deaths due to diseases prevented by vaccines recommended before 1980 were shown for diphtheria, mumps, pertussis, and tetanus.

•Endemic transmission of poliovirus and measles and rubella viruses has been eliminated in the United States; smallpox has been eradicated worldwide.

•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.

For newer diseases like COVID-19, data shows vaccines are proving effective against existing variants, especially at preventing severe disease, hospitalization and death.

Efficacy vs. Effectiveness and Limitations

Effectiveness is measured in two ways:

•Vaccine efficacy is measured in controlled clinical trials

•Vaccine effectiveness refers to how well vaccines work in the real world. Effectiveness can differ from efficacy because we can’t predict exactly how effective vaccination will be for a much bigger and more variable population.

Vaccines are not 100% effective for every person:

> Vaccines can stop most people from getting sick, but not everyone.
> If vaccinated people do get sick, they are likely to have milder symptoms, in general 'It is very rare for someone vaccinated to experience severe illness or die.

Protection may also weaken over time and require booster doses, and viruses can change over time to produce new variants. Vaccines are therefore monitored for ongoing safety and effectiveness after approval, and booster doses help strengthen and extend the protection.

In summary, while no vaccine provides absolute protection for 100% of recipients and effectiveness varies by disease, age, health status and variant, the scientific consensus and decades of global data show vaccines are a highly effective, safe, and cost-effective tool for preventing infectious diseases, reducing severe illness, hospitalizations, deaths, and in some cases achieving eradication or elimination.

Citations (3)

1who.intGovernment
Vaccines and immunization: Vaccine safety
Backs: “Over the past 50 years, essential vaccines against just 14 diseases have saved at least 154 million lives (1).”
2who.intGovernment
Vaccines and immunization
Backs: “Over the past 50 years, essential vaccines against just 14 diseases have saved at least 154 million lives (1). During the same period, vaccination has contributed to 40% of the drop in infant deaths.”
3who.intGovernment
Vaccine efficacy, effectiveness and protection
Backs: “For newer diseases like COVID-19, data shows vaccines are proving effective against existing variants, especially at preventing severe disease, hospitalization and death. Efficacy vs. Effectiveness and Limitations”