The world is waiting anxiously for a COVID-19 vaccine, but how do vaccines even work? Here’s what you need to know.

The U.S. woke up to exciting news on Monday: the potential of a very effective COVID-19 vaccine. Pharmaceutical company Pfizer announced that early data from its vaccine trial suggests that its two-dose vaccine is 90 percent effective at preventing COVID-19, without any serious safety concerns. (The results of its trial have yet to be published in a peer-reviewed scientific journal, and Pfizer has not shared the nitty-gritty of its data with the public yet.) This is heartening news, given that any vaccine for COVID-19 will be of the highest stakes for the entire global population.

While we wait for a final vaccine to roll out to the global population, biochemist, neurobiologist, and antibody engineer Esther Odekunle, PhD, has some insight to share about how the vaccine development process works. In the latest episode of Well+Good’s YouTube series Need to Know, she answers host Sophia Bush’s most pressing questions about the COVID-19 vaccine—starting with the basics of what a vaccine even is. “A vaccine is a substance that stimulates your body’s immune system to fight against, and therefore protect you against, a pathogen, and a pathogen is anything that causes disease,” Dr. Odekunle explains.

Getting naturally infected with a pathogen, like the SARS-CoV-2 virus, creates an immune response in your body that works to fight off that pathogen, says Dr. Odenkunle. Vaccines cheat this process by providing your body with defenses against the pathogen without requiring you to actually suffer through its potential effects (aka, getting really sick) first. “Depending on the effectiveness of the vaccine, it could provide full immunity, which would mean you will not be infected when exposed to the pathogen, or if full immunity is not possible, it could lessen the severity or duration of the infection,” she says. In this particular case, then, the aim of the COVID-19 vaccine is to prevent you from getting sick, or at least very sick, from the coronavirus should you come into contact with it.

Dr. Odekunle offers a lot more insights into the vaccine-making process, including explanations on the four types of vaccines (and which kind the COVID-19 vaccine likely will be) and what to expect when it finally arrives. Will we, Bush asks, be able to take off our masks at long last? Watch the video for the answer, and to find out which detail of the vaccine development process makes both women feel all the feelings. Says Bush, “It actually strikes me as quite beautiful.”

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