Are vaccines an effective tool to prevent disease?

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

Yes, vaccines are an effective tool to prevent disease.

Evidence from the World Health Organization (WHO), Centers for Disease Control and Prevention (CDC) and other health authorities shows:

1. How vaccines prevent disease

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

They do this by priming a person's immune system to recognise a specific disease-causing bacteria, virus or other pathogen. This "memory" can last years, or in some cases for life, which is why vaccination can be so effective, stopping people from getting sick rather than waiting until disease occurs.

Specifically:
> Vaccines contain weakened or inactive parts of a particular organism (antigen) that triggers an immune response within the body
> this weakened version will not cause the disease in the person receiving the vaccine, but it will prompt their immune system to respond much as it would have on its first reaction to the actual pathogen

Once exposed to one or more doses of a vaccine, we typically remain protected against a disease for years, decades or even a lifetime. This is what makes vaccines so effective. Rather than treating a disease after it occurs, vaccines prevent us in the first instance from getting sick.

We now have vaccines to prevent more than 30 life-threatening diseases and infections, helping people of all ages live longer, healthier lives.

Vaccines are also critical to the prevention and control of infectious disease outbreaks. They underpin global health security and are a vital tool in the battle against antimicrobial resistance.

Vaccines are safe, effective and life-saving. Before approval by relevant regulatory agencies, vaccines undergo rigorous clinical trials to test their quality, safety and efficacy.

2. Measured effectiveness

Vaccine efficacy is measured in controlled clinical trials. It is based on how many people who got vaccinated developed the 'outcome of interest' compared with how many people who got the placebo developed the same outcome. Vaccine effectiveness refers to how well vaccines work in the real world.

Examples:

•Based on what we know so far, vaccines are proving effective against existing variants, especially at preventing severe disease, hospitalization and death.

•A new CDC study showing that COVID-19 mRNA vaccines authorized by the Food and Drug Administration (FDA) protect health care personnel against COVID-19. mRNA vaccines (Pfizer-BioNTech and Moderna) reduced the risk of getting sick with COVID-19 by 94% among HCP who were fully vaccinated

•Vaccines can stop most people from getting sick, but not everyone. Even after someone receives all of the recommended doses and waits a few weeks for immunity to build up, there is still a chance that they can get infected. Vaccines do not provide full (100%) protection

•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 from the initial dose or primary series may weaken over time. Booster doses help strengthen and extend the protection

Herd immunity also contributes: When a lot of people in a community are vaccinated the pathogen has a hard time circulating because most of the people it encounters are immune.

3. Population-level impact

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

•Over 50 years, vaccines against 14 diseases—diphtheria, Haemophilus influenza type B, hepatitis B, Japanese encephalitis, measles, meningitis A, pertussis, invasive pneumococcal disease, polio, rotavirus, rubella, tetanus, tuberculosis, and yellow fever—had directly contributed to reducing infant deaths by 40 percent

•WHO estimates that a study found vaccines have saved at least 154 million lives over 50 years, and vaccines are among the most powerful inventions in history, making once-feared diseases preventable

•The greatest triumph of immunization was the eradication of smallpox in 1977. An astounding 3 million lives per year have been saved through this first-ever eradication of a disease

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

•Among U.S. children born from 1994 to 2013, vaccines will prevent about 322 million illnesses, 21 million hospitalizations, and 732,000 deaths.

At an individual level, vaccines are very effective at providing protection against certain diseases, though they don't provide immunity in 100 per cent of cases.

In summary, according to WHO and CDC, vaccines are a highly effective, safe and cost-effective public health intervention to prevent infection, severe illness, complications, hospitalization, death, and onward transmission of more than 30 diseases.

This information is for educational purposes and does not constitute medical advice. Talk to a health-care provider to find out what vaccinations are needed for you and your family.

Citations (3)

1who.intGovernment
Vaccines and immunization
Backs: “Vaccines reduce risks of getting a disease by working with your body's natural defenses to build protection.”
2who.intGovernment
How do vaccines work
Backs: “This "memory" can last years, or in some cases for life, which is why vaccination can be so effective, stopping people from getting sick rather than waiting until disease occurs. Specifically: Vaccines contain weakened or inactive parts of a particular organism (antigen) that triggers an immune response within the body”
3who.intGovernment
Vaccine efficacy, effectiveness and protection
Backs: “They underpin global health security and are a vital tool in the battle against antimicrobial resistance. Vaccines are safe, effective and life-saving. Before approval by relevant regulatory agencies, vaccines undergo rigorous clinical trials to test their quality, safety and efficacy.”