The world’s scientific and medical communities all agree: Vaccines are one of the safest guards for population health in history.

Every single day, around the world, vaccines save children’s lives. Throughout history, pandemics have swept through populations, killing millions of people, disrupting generations of societies. For diseases that weren’t deadly, epidemics left generation after generation of children exposed to debilitating diseases that left them unable to see, hear, walk, and talk.

Take Action: Where You Live Shouldn’t Decide Whether You Live. Demand World Leaders Invest in Vaccines

But vaccines — and the scientific revolution that brought them about — have changed all of that. Today, most kids don’t get measles, polio, or smallpox. In fact, kids don’t even have to get chickenpox anymore thanks to vaccines.

Yet distrust of vaccine persists. Most of that distrust is attributed to now-debunked study that was published in a medical journal in the United Kingdom years ago, but the jitters remain.

To help clear up any confusion, Global Citizen brings you a quick guide to the vaccine myths you may have heard, but you shouldn’t believe.

Read More: Study: Vaccines Have Prevented 450,000 Deaths in US Since 1963

1. Vaccines Are No Longer Needed

Some people think that vaccines are unnecessary as long as good hygiene is maintained; that is, that clean water, nutrition, and sanitation alone can prevent diseases. Unfortunately, those things aren’t enough. The diseases that have been prevented by vaccines can spread even in the most hygienic conditions. Infectious diseases like whooping cough, polio, and measles could all reappear if optimum rates of immunization in a population (or “herd immunity” — the idea of protecting an entire population through mass vaccination) are maintained, according to the World Health Organization.

2. Vaccines Aren’t Safe

Vaccines are among the most rigorously tested medicines on the planet. From the time a potential vaccine is discovered until it is adopted for use, it has typically gone through years of testing and trials; once it is released, scientists continue to monitor the results for any changes in outcomes, according to the WHO. Vaccines can cause reactions, but they often include temporary effects like soreness or a mild fever, but vaccines with any more serious effects than that are quickly taken off the market.

More importantly, people in all parts of the world are more likely to be harmed by vaccine-preventable diseases than by vaccines. Polio can cause paralysis; its vaccine cannot.

Read More: Vaccines Are So Clearly Effective, Even Congress Agrees They Are Safe

3. Getting Infections Helps Build Immunity Better Than Vaccines

Vaccines are designed to produce optimum immunity. They produce similar immunity to actually getting the disease without the dangers of actually having the disease itself. Again, having the disease poses greater risk, according to the WHO.

4. Vaccines Aren’t Needed If a Disease Doesn’t Exist in a Country

One of the things we learned from the Ebola outbreak was how quickly diseases can travel. Infectious agents circulating in one part of the world can quickly show up in another part in today’s interconnected world. So if a measles outbreak occurs in Australia, and someone unknowingly carries it to the United States, an unvaccinated person in the US could quickly become infected and spread the disease.

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5. Vaccines & Autism: A Reality Check

It’s time this myth was put to rest. The study that originally proposed a link between to autism and the measles vaccine, published nearly two decades ago, was found to be fraudulent and was retracted. The panic it caused has lingered, posing real dangers to the health of the global population, according to WHO.

One more time, for emphasis: There is no evidence of a link between MMR vaccine and autism or autistic disorders.

Read More: Everything You Need to Know About the Anti-Vaxxer Movement