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Your most Googled questions about vaccines


Vaccines are undoubtedly one of the most important health tools at our disposal. But many people still have questions about what exactly they are and how they work.

Having safe and effective vaccines to fight COVID-19 within a full year of the first reported cases is a major scientific achievement. Now, understanding the basics of how vaccines work is more important than ever so everyone is well-informed about this crucial life-saving tool.

That’s why we want to make sure everyone has all the need-to-know facts about this tiny but mighty health intervention.

Why are vaccines important?

Short answer: vaccines save lives.

Long answer: immunisation is considered to be one of the most miraculous advances of modern medicine. Vaccines save up to up to 5 million lives per year and have contributed to a 60% drop in child mortality since 1990.

On top of the lives saved, vaccination also helps combat poverty and ensure more people get primary healthcare.

What do vaccines prevent?

Vaccines prevent some of the world’s deadliest and infectious diseases including measles, pneumonia, whooping cough, influenza, HPV, and cholera. In 2019 Gavi helped ensure that the newly created Ebola vaccine reached the people most in need. Now, Gavi is helping ensure equitable access to COVID-19 vaccines by co-leading COVAX, a pillar of the Access to COVID-19 Tools Accelerator (ACT-A). Learn more about how COVID-19 vaccines were developed.

Today, a number of other vaccines are still under development, including a universal influenza disease vaccine. To date, smallpox is the only disease to be entirely eradicated by vaccines, though there is hope that polio may soon follow.

What are the economic impacts of vaccines?

Vaccines lead to economic benefits for families and society alike.

Sickness can put a big financial strain on people and their families. Think about it this way: if a child is sick, they can’t go to school and often their parents can’t go to work. This can make short-term expenses pile up – like transportation to the health clinic, medical bills, and loss of income from taking time off of work. Longer-term, the economic impact of illness can include overall loss of productivity from disability or death.

Vaccination helps people avoid these costs through keeping people healthy, and the savings add up. For every US$1 spent on vaccines in Gavi-supported countries, the global economy gets a return of US$54. This resulted in over US$150 million in economic benefits from 2000 to 2017, thanks to Gavi.

COVID-19 has also proven that unequal access to vaccines can cost the global economy. Vaccine nationalism in rich countries and unequal COVID-19 vaccine distribution could cost the world economy an additional US$9.2 trillion, with rich countries bearing 75% of that global economic loss. Learn more about the potential economic impacts with our Vaccine Access Test and in our animated series “Pandemica.”

What would happen if the world didn’t have vaccines?

Without vaccines, millions of people wouldn’t be alive. Smallpox, one of the most devastating diseases in the world, might still exist. As for the economy, the devastating initial impacts of COVID-19 happened because we were just missing one vaccine. Now, imagine the impact with no vaccines at all, or the devastating economic impact if the world does not prioritize global vaccine distribution.

There’s no telling what specific effects those losses would have on the world, but it’s safe to say that the world is in a much better place because of vaccines. Regardless of the past, this is an important question for the present. Given what we know about the benefits of vaccines, we have a choice on what will happen based on how we use vaccines today.

What exactly are vaccines?

Vaccines are a way of inoculating people, which is intentional exposure to a disease in order to build immunity against that disease. Vaccines work by containing the same germs that cause the disease it’s protecting against. These germs are weakened or killed before entering the body, so they don’t lead to infection.

Where did vaccines come from?

The history of vaccination starts long before the first known vaccine. There’s evidence that people were inoculating against smallpox as early as the year 1000 CE in China.

It wasn’t until 1796 that Edward Jenner produced what is known as the first vaccine. He used cowpox pustules to immunise against smallpox. His invention was followed by 200+ years of research and innovation to create the vaccines we have today, and that work continues to this day.

In 2000, Gavi was founded to greatly expand the reach of vaccines worldwide, playing a key role in the modern history of vaccines. In just over two decades, Gavi has helped immunise 822 million children and save over 14 million lives.

How do vaccines work?

The germs in the vaccines mimic a real infection, causing your immune system to develop antibodies against that disease. As a result, you build up immunity to a disease without actually having the disease.

How do vaccinations improve global health?

When someone is vaccinated, the impacts extend far beyond that one person. When more people in a community are immune to a disease, it’s more difficult for the disease to spread from person to person. This is called community immunity, or herd immunity, and it decreases the likelihood of anyone getting that disease. Community immunity is especially important for people who cannot get vaccinated due to pre-existing conditions or age.

On top of the benefits of immunity, vaccines can help get more people into primary healthcare. Taking a child to get their vaccinations gives families regular contact with healthcare professionals, which can be used to discuss more than just vaccination. Taking a child in for vaccination doesn’t just protect against a specific disease — it gives families an opportunity to improve overall health.

Are vaccines safe?

Yes, vaccines are safe. Because of how many people worldwide rely on vaccination to stay healthy, ensuring the safety of vaccines is a priority among researchers and scientists.

When a vaccine is in development, it goes through rigorous testing to ensure that it is safe and effective. Once approved for use, every batch of vaccinations is also tested and monitored before being sent out. If you’re interested in every stage of testing for vaccines, from development to doctor’s office, you can read more here.

Can vaccines make you sick?

Although vaccines contain germs from diseases, they do not cause sickness. The germs in vaccines are either weak or dead, and dead viruses cannot cause a disease. With live vaccines, there might be what appears to be a “mild case of the disease,” but this is not harmful — “a vaccine causing a full-blown disease would be extremely unlikely.”

It is possible to have some side effects from vaccines, like soreness where the injection happened or a slight fever. The side effects depend on the vaccine, but none of them cause sickness.

What can I do to support vaccination and vaccine access?

Now that you know all about vaccines, you can do your part to ensure that everyone, everywhere has equal access both to COVID-19 vaccines and to routine immunisations.

Pandemics and diseases know no borders and require collective global action, so by joining ONE’s mission, you’ll help demand a global response to COVID-19, encourage world leaders to share surplus vaccine doses and stop vaccine nationalism, and help support organisations like Gavi in making sure people everywhere have access to vaccines.

Learn more with our Vaccine Access Test and watch Pandemica now.

This article was originally published in March 2020 and updated in April 2021.

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