Are vaccines an effective tool to prevent disease?

Yes

Yes, vaccines are highly effective tools for preventing disease. Global scientific and medical consensus overwhelmingly supports vaccination as one of the most successful and cost-effective public health interventions in history.

Below is an overview of how vaccines work, the evidence of their effectiveness, and why they are so critical to global health.

1. How Vaccines Work

Vaccines prevent disease by working with your body’s natural defenses to build immunity safely. They introduce a harmless, weakened, or inactive part of a pathogen (like a virus or bacteria), or a blueprint for making a harmless part (like mRNA).

This trains your immune system to produce antibodies and memory cells. If you are ever exposed to the actual pathogen in the future, your immune system is already prepared to recognize and destroy it before it causes severe illness. Because vaccines only contain weakened or inactive forms of a germ (or parts of it), they do not cause the disease itself.

2. Evidence of Effectiveness

The real-world impact of vaccines is backed by extensive historical and modern data:

•Saving Millions of Lives Annually: According to the World Health Organization (WHO), immunization currently prevents between 3.5 million and 5 million deaths every year from diseases like diphtheria, tetanus, pertussis (whooping cough), influenza, and measles.

•Long-Term Protection: The U.S. Centers for Disease Control and Prevention (CDC) estimates that routine childhood vaccinations for Americans born between 1994 and 2023 will prevent about 508 million illnesses, 32 million hospitalizations, and save over 1.1 million lives.

•Eradication of Deadly Pathogens: Vaccines successfully eradicated smallpox globally, one of the deadliest human diseases in history. They have also brought polio to the brink of global eradication.

3. Efficacy vs. Real-World Effectiveness

When discussing how well vaccines work, scientists look at two measures:

•Vaccine Efficacy: This is measured in controlled clinical trials. For example, if a vaccine has an 80% efficacy in a trial, it means vaccinated participants had an 80% lower risk of getting sick compared to those who received a placebo.

•Vaccine Effectiveness: This measures how well vaccines work in the "real world" across a much larger, more diverse population.

While no vaccine is 100% effective for everyone due to differences in individual immune systems, they remain incredibly powerful. Even in cases of "breakthrough infections" (where a fully vaccinated person still gets sick), vaccines dramatically reduce the risk of severe illness, hospitalization, and death.

4. Broader Benefits of Vaccination

Beyond protecting individuals, vaccines provide major societal and economic benefits:

•Herd Immunity: When a high percentage of a community is vaccinated, it becomes difficult for a disease to spread. This helps protect vulnerable individuals who cannot be vaccinated, such as infants, the elderly, or people with weakened immune systems.

•Outbreak Prevention: Vaccines act as a barrier to prevent infectious disease outbreaks from turning into pandemics.

•Economic Value: Vaccination is highly cost-effective. The CDC notes that for every dollar spent on childhood immunizations in low- and middle-income countries, approximately $52 is saved in healthcare costs and economic productivity lost to illness.

•Combating Superbugs: By preventing bacterial infections and viral infections (which might otherwise be inappropriately treated with antibiotics), vaccines help slow the rise of drug-resistant bacteria (antimicrobial resistance).

Citations (5)

1cdc.govGovernment
cdc.gov
Backs: “Yes, vaccines are highly effective tools for preventing disease. Global scientific and medical consensus overwhelmingly supports vaccination as one of the most successful and cost-effective public health interventions in history.”
attribution, other, points to yes. Claim: Global scientific and medical consensus supports vaccination as one of the most successful and cost-effective public health interventions in history.
2who.intGovernment
who.int
Backs: “Yes, vaccines are highly effective tools for preventing disease. Global scientific and medical consensus overwhelmingly supports vaccination as one of the most successful and cost-effective public health interventions in history.”
attribution, other, points to yes. Claim: Global scientific and medical consensus supports vaccination as one of the most successful and cost-effective public health interventions in history.
3cdc.govGovernment
cdc.gov
Backs: “Long-Term Protection: The U.S. Centers for Disease Control and Prevention (CDC) estimates that routine childhood vaccinations for Americans born between 1994 and 2023 will prevent about 508 million illnesses, 32 million hospitalizations, and save over 1.1 million lives. Eradication of Deadly Pathogens: Vaccines…”
statistic, other, points to yes. Claim: CDC estimates routine childhood vaccinations for those born 1994-2023 prevent 508 million illnesses, 32 million hospitalizations, and over 1.1 million deaths.
4who.intGovernment
who.int
Backs: “When discussing how well vaccines work, scientists look at two measures: Vaccine Efficacy: This is measured in controlled clinical trials.”
background, other, points to yes. Claim: Scientists assess vaccines using two measures: efficacy in trials and effectiveness in the real world.
5cdc.govGovernment
cdc.gov
Backs: “Vaccine Effectiveness: This measures how well vaccines work in the "real world" across a much larger, more diverse population.”
background, other, points to yes. Claim: Vaccine effectiveness measures how well vaccines work in the real world across a larger, more diverse population.