Why Does It Take So Long To Create A Vaccine?

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Until a vaccine for COVID-19 is approved, social distancing and sheltering-in-place measures are the most effective ways to prevent the spread of this novel respiratory virus. Vaccines, of course, have eradicated tons of deadly illnesses throughout history, from the mumps to smallpox and polio and much more. They've greatly increased the average life expectancy. 

"When you receive a vaccination, your body develops an immune response to a weakened or altered virus," says Marcus Zervos, M.D., an infectious disease specialist with Henry Ford Health System. "Your body builds up antibodies so if you're exposed to that virus in the future, you can fight it off before you get an infection." 

Dr. Zervos says the soonest a COVID-19 vaccine could be ready for widespread use will be 18 months from nowand if that's the case, it will be the fastest a vaccine has ever been developed. 

"The AIDS vaccine has been worked on for 20 years or more, for example, and it's still not out," says Dr. Zervos. "But other vaccines have been developed more quickly than that, and our hope is that this one will be ready in 18 months, although there's always the possibility it doesn't work and you have to start over." 

Ideally, current social-distancing measures will eliminate COVID-19 and we won't see it again, he says. But if it does come back next winter, hopefully we will be ready with a vaccine. 

Step-By-Step: How A Vaccine Is Made

So, why does it take so long to develop a vaccine? In order to answer that question, you need to know how a vaccine is created. Here, Dr. Zervos shares the steps it takes to create one: 

1. Determine the genetic sequence of the virus. (Thankfully, scientists cracked COVID-19's code in record time.) 

2. Develop a vaccine using one of a few different strategies. These include:

  • Inactivate the virus so that, while keeping its major components, it won't cause infection. 
  • Heavily weaken a strain of the vaccine so that it won't cause infection. Technically, it will still be alive, but it won't be strong enough to cause harm. This is called an attenuated vaccine, and it's how both the measles and some flu vaccines have been created. 
  • Pull out specific components of the virus (i.e., parts of its genetic sequence, instead of the full genetic code) and use that as a vaccine, so that your body will recognize it and build up antibodies without getting an infection. "This is a fairly novel way of creating a vaccine, and it's one method that's being used with COVID-19," says Dr. Zervos. "Several different vaccines are being studied."

3. Start the first clinical trials using healthy, normal volunteers. "These first clinical trials measure the antibodies in the blood and ensure there aren't any dangers associated with the vaccine," says Dr. Zervos. "This is the stage we're in right now. We're just looking at safety and antibody response." 

4. Begin the second round of clinical trials in larger populations of people who are at risk for infection. (In this case, for example, healthcare workers.) Any adverse side effects are recorded in registries. "This stage is conducted in thousands of people, and it takes time to go through these studies," Dr. Zervos says. 

5. Approve vaccine for widespread use. When scientists are confident that a vaccine works, it gets massed produced for large populations. "When you use a vaccine in millions of people, you might see a side effect that wasn't previously noted, and so that gets recorded," says Dr. Zervos. "This stage—right after it's approvedis called post-approval monitoring." 

Although these steps may seem fairly straight forward, each phase takes plenty of time and coordination from researchers and doctors in order to ensure safety and precision. The more conscientious they are the first time, the higher the likelihood they'll get it right on the first try. 


If you're experiencing symptoms and are concerned about possibly having COVID-19, use this online screening tool to help you learn more about your risk and get recommended next steps. 

For up-to-date information about Henry Ford Health System's response to the coronavirus, visit henryford.com/coronavirus

Dr. Marcus Zervos is a doctor specializing in infectious disease and sees patients at Henry Ford Hospital in Detroit and Henry Ford West Bloomfield Hospital. 

Categories: FeelWell