Vaccines are a proven way to prevent disease — I'll pull the latest evidence on how well they work.
Yes, vaccines are one of the most effective tools to prevent disease.
Evidence of effectiveness
•Vaccination is described by the World Health Organization (WHO) as 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.
•Immunization currently prevents 3.5 million to 5 million deaths every year from diseases like diphtheria, tetanus, pertussis (whooping cough), influenza and measles.
•Vaccines are also described as critical to the prevention and control of infectious disease outbreaks.
•Research reviews conclude: "Vaccines remain the most consistently effective intervention against infectious diseases such as smallpox, rabies, polio, and various childhood illnesses"
Historical impact on incidence is large:
•Vaccines are among the most cost-effective ways to protect against infectious diseases, and introduction of a vaccine has in many cases led to a very large decrease in incidence — 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
•Smallpox vaccine is described as very effective as the smallpox virus is now completely gone
How they work
•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.
•More specifically, vaccines work by introducing a weakened or inactive version of the disease-causing agent to the body to trigger active immunity.
•They work by training our immune system to recognize and fight pathogens, either through introducing a weakened or dead version of the pathogen, or a part of it, like its proteins. This exposure triggers the body to produce antibodies without causing the disease itself
Level of protection
Vaccines are highly effective but not 100% perfect for every person, and effectiveness varies by vaccine and disease:
•For varicella (chickenpox) overall vaccine effectiveness is 82% after 1 dose and 92 to 98% after 2 doses; effectiveness against severe varicella is 100% after even 1 dose
•A sweeping global review found that mRNA vaccines — now administered billions of times worldwide — are safe and highly effective at preventing infectious diseases like COVID-19
•One study found that an up-to-date COVID-19 vaccine received within the past six months was 72 per cent effective at preventing hospitalization and 67 per cent effective at preventing the most serious outcomes, including ICU admission and death.
•Based on what we know so far, vaccines are proving effective against existing variants, especially at preventing severe disease, hospitalization and death. However, some variants are having a slight impact on the ability of vaccines to guard against mild disease and infection.
Vaccines are likely staying effective against variants because of the broad immune response they cause.
Community-level protection (herd immunity)
•Vaccination will prevent illness in an individual by providing artificial immunity — Consequently, vaccines reduce the likelihood that an infected individual will spread the pathogen they have been vaccinated against to others — This is the principle behind the idea of herd immunity
•Vaccines are one of the most effective tools we have in preventing diseases and achieving herd immunity
•Herd immunity describes how a population is protected from a disease after vaccination by stopping the germ responsible for the infection being transmitted between people
In summary, scientific consensus and decades of global data show vaccination is one of the most life-saving and effective public health interventions in history for preventing infectious disease, reducing severe illness, death, and transmission at both individual and population levels, while like any medical intervention protection is not absolute and is monitored for safety and effectiveness over time.