Are vaccines an effective tool to prevent disease?

Vaccines are one of the best-proven tools for preventing disease — I'll pull the latest evidence to show how well they work.

Yes — vaccines are one of the most effective tools ever developed to prevent disease.

How vaccines prevent disease

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

> Vaccines work by producing an immune response in the body without causing illness

They work by using dead or weakened viruses to trick our bodies into thinking we have already had the disease. When you get a vaccine, your immune system responds to these weakened ‘invaders’ and creates antibodies to protect you against future infection

Vaccines contain weakened or inactive versions of pathogens or their components and your immune system responds by creating T cells and B cells that specifically recognize and remember that pathogen, producing long-term immunity as they cause memory cells to be created.

Vaccines also protect communities through herd immunity:

> Herd immunity, or community immunity, means there are enough people immunised in the community to slow or stop the spread of disease

When enough people are immune, it creates a protective barrier for the whole population because there are very few places for the pathogen to breed, so vaccinated people are less likely to pass it on to others and unvaccinated individuals gain indirect protection.

It is important that people are aware of the broader protection that vaccination can provide and continue to trust in vaccines as one of the most effective tools to prevent diseases

Evidence of effectiveness

Global 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 the past 50 years, essential vaccines against just 14 diseases have saved at least 154 million lives

The World Health Organization also estimates that over the last 50 years 154 million lives have been saved by immunizations, that is an estimated 6 lives every minute of every year.

> 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 among the safest and most effective public health tools, preventing 3.5–5 million deaths every year.

Research modeling 50 years of the Expanded Programme on Immunization found that during the same period, vaccination has contributed to 40% of the drop in infant deaths.

Disease-specific successes:

Recent US data:

> Research shows that routine vaccinations for children born during 1994–2023 will have prevented about 508 million illnesses and 32 million hospitalizations and saved over 1.1 million lives

According to CDC data from 2023, unvaccinated individuals were 6x more likely to be hospitalized and 12x more likely to die from COVID-19 than those who were fully vaccinated and boosted. Effectiveness for COVID-19 vaccines is not absolute prevention of infection but measurable reduction in severe outcomes— many studies emphasize strong protection, especially against hospitalization and critical illness in older adults.

> Vaccines cannot always prevent infection, but they can substantially reduce the risk of serious disease

Vaccination not only prevents disease caused by acute infection but also protects against long-term immune-related sequelae that can follow an acute viral infection.

Are vaccines perfect?

No vaccine is 100% effective for every person, effectiveness varies by vaccine, age, and immune status, and protection can wane over time requiring boosters. Like any medicine, vaccines can cause side effects, however, these are usually very minor and of short duration, such as a sore arm or a mild fever. More serious side effects are possible but extremely rare.

Before any vaccine is introduced, the vaccine undergoes rigorous and stringent testing through multiple phases of clinical trials and after introduction, national health authorities continuously monitor vaccine safety.

A person is far more likely to be seriously harmed by a disease than by a vaccine. Vaccine-preventable diseases like measles, meningitis, hepatitis B or polio can be deadly or cause severe illness and disability.

In summary, the scientific consensus from WHO, CDC and large global reviews is that vaccines are highly effective at preventing illness, severe complications, hospitalization, disability and death from more than 30 infectious diseases, and have saved hundreds of millions of lives through individual protection and community (herd) immunity.