How does a vaccine work? An expert breaks it down

Marya Ghazipura, epidemiologist and biostatician based in New York City talks to Yahoo Life about all things vaccines: What is a vaccine? How is it made? How long does it take? The purpose of a vaccine is to train our bodies to create an immune response to pathogens so that we can successfully neutralize a virus when we come in contact with it in the future. “A pathogen is a protein that’s foreign to your body, like a virus or bacteria,” Ghazipura explains. “The idea is that we want our bodies to create antibodies against it.” In order to create these antibodies to act as a defense mechanism, we first need to be exposed to the virus via an antigen in a vaccine. “Antigens are proteins that are on the surface of the virus, they look like the pathogen but they’re inactive or they’re weakened,” she says. Once we are exposed to these antigens via a vaccine, our bodies learn to recognize them as a hostile invader, creating antibodies to fight them off. “That way in the future when you’re challenged with the virus, your body already recognizes it as a foreign object, and it has adequate storage of antibodies to neutralize the virus,” Ghazipura tells Yahoo Life. “Vaccines don’t just work at an individual level, sure they protect us, but they also work at this population level,” she explains. “This results in something called herd immunity.” Ghazipura explains that if enough people are immune through vaccinations, the virus stops finding enough hosts and eventually starts dying out. That’s why it’s important that as many people as possible become vaccinated. Ghazipura says that the process to develop a virus is made up of 5 key phases that can take up to 5 years, but science is being expedited at unprecedented rates to stop the spread of COVID-19. Once all phases are complete including three levels of clinical trials involving thousands of volunteers, a vaccine is approved and moves on to mass production. Ghazipura says that although push back against science is at an all-time high, in order for a vaccine to work properly, we need everyone on board. “We want as few people as possible to be contagious, and in order to make that happen we need higher vaccine uptake,” Ghazipura says.

Video transcript

MARYA GHAZIPURA: My name is Marya Ghazipura. And I'm an epidemiologist and biostatistician here in New York City. A vaccine is a therapeutic drug. And it works by teaching our immune system to recognize and combat any sort of foreign pathogen.

A pathogen is a protein that's foreign to your body-- viruses or bacteria. The idea is that we want our bodies to create antibodies against it. And these antibodies are a little defense mechanism. They're little soldiers inside our bodies that attack this foreign body and try to destroy it.

But in order for our bodies to recognize these pathogens as being foreign, your body needs to be exposed to the virus. Antigens are proteins that are on the surface of the virus. They look like the pathogen, but they're inactive or they're weakened.

And when these antigens are delivered into our body through a vaccine, our immune system learns to recognize them as a hostile invader. So that way in the future, when you're challenged with the virus, your body already recognizes it as a foreign object. And it has adequate stores of antibodies to neutralize the virus.

Now a key thing to remember here is that vaccines don't just work at an individual level. Sure, they protect us, but they also work at this population level. This results in something called herd immunity. Essentially, if large portions of the population are immune through vaccinations, the virus itself cannot sustain and it slowly starts dying out.

There are five key stages to vaccine development. The first stage, which can take from months to years, is this exploratory phase. And the idea is that we really want to understand the virus. We look at them in the labs. We look at them in animal cultures.

And then, and only then, do we enter something called a preclinical phase. And we're really looking at whether or not this vaccine is safe. After the preclinical phase, we move on to clinicals.

Now in phase one in the clinical stage, we look at the safety of the vaccine. And it only includes about a few dozen people.

Moving on to phase two, we now have hundreds of people. And here we look at what's the right dosage? Is it going to be injected? Is it going to be inhaled?

The third phase is basically when we have thousands of people in a randomized trial. It looks at safety and efficacy on a much larger scale. Vaccine development then concludes with regulatory approvals. And then there's mass production.

The average vaccine can take about five years to develop. Science has mobilized in unprecedented ways to battle COVID-19. They're being rushed and they are being expedited, but they're being done in a way that, ideally, is safe and effective. Once a safe and effective vaccine is made available, to arrive at herd immunity, we need everyone on board.

The pushback against scientific recommendations is also at an unprecedented high in our current climate. We've seen this play out in the controversy over wearing masks. And so it's important that safety data are made very clear and public for the general public to trust in our fast-track processes.

We want as few people as possible to be contagious. And in order to make that happen, we need higher vaccine uptake.