Coronavirus vaccines 101: What you need to know

Staggering global investment in vaccine development and production could well lead to the fastest vaccine turnaround in human history.
August 10th, 2020
nurse with mask and shield readies a coronavirus vaccine for a patient wearing a mask.
It’s a race to find a coronavirus vaccine, but there are many questions around vaccines. Here is what you need to know. Photo: Getty Images.

UCHealth is hosting a major clinical trial: the trial of Moderna’s experimental vaccine at UCHealth University of Colorado Hospital on the Anschutz Medical Campus, which aims to enroll 1,000 patients. Across the globe, several vaccine makers are racing to create and test vaccines that they hope will work to prevent COVID-19. It’s helpful to go over the basics. Here’s what you need to know about coronavirus vaccines.

What is a vaccine?

Think of a vaccine as forcing a practice session on the immune system. Vaccines give the body a sneak peek at one or more key features of a virus before the actual virus barges in. The immune system then develops a “memory” of a virus.

How will vaccines for the new coronavirus work?

Typically, these vaccines will latch either directly or indirectly onto the spike protein that makes coronaviruses unique. (Coronaviruses got their name because the viruses have spikes that look like a crown.)

Once prepped, the immune system can quickly recognize actual coronaviruses should they invade, interfere with a virus’s ability to multiply, and call into action other parts of the immune system. The idea is to stop SARS-CoV-2, the virus that causes COVID-19, from getting into cells, replicating itself and making a person sick.

Are these vaccines safe?

Vaccines are, in general, overwhelmingly safe – even more so when one considers the personal and societal costs of the diseases they prevent. The same should hold true with the coronavirus vaccines under development. Coronavirus vaccines use different approaches, but none involve viruses that can multiply and cause disease. They’re designed to sharpen the immune system by introducing inactivated viruses, viral proteins, or genetic instructions (RNA or DNA) that tell the recipient’s cells to produce viral proteins for the immune system’s training.

Why do I keep hearing people talk about vaccines that are “safe and effective?”

The 1986 National Childhood Vaccine Injury Act requires that vaccines be both “safe and effective.”

According to the Centers for Disease Control and Prevention, during the 1970s, consumers became more concerned about vaccine safety. Several lawsuits were filed against vaccine manufacturers and health care providers by people who believed they were injured by the diphtheria, pertussis and tetanus (DPT) vaccines. Some people won financial awards despite lack of evidence to support vaccine injury claims. To reduce liability and respond to public health concerns, Congress took action and passed the act in 1986.

I also hear about people who oppose vaccines. Is there any scientific evidence to support this point of view?

No. In fact, vaccines have led to some of the most remarkable public health success stories in history. Thanks to vaccines, health leaders have eradicated smallpox and nearly eliminated cases of polio around the world. Many vaccine skeptics believe that vaccines make people sick, in large part because of fraudulent and discredited research. In fact, research shows the opposite. Vaccines save lives.

How soon will coronavirus vaccines be ready?

While no one knows the timing for sure. The fastest that the first vaccine trials are expected to yield an FDA-approved vaccine would be late this year or early next. Of course, if you happen to be a Chinese soldier, you may already have been vaccinated by an experimental CanSino Biologics vaccine.

How soon could I get a vaccine?

Vaccine developers are racing to make them available as quickly as humanly possible, but it could be months before vaccines are ready for the public. That’s despite heroic efforts to smash the current vaccine-development speed record. (The mumps vaccine took four years.) Assuming a booster is required, immunizing the U.S. population would involve more than 650 million injections. Globally, think 14 billion shots.

Has there ever been a vaccine for another coronavirus?

None that has been approved for use with people, though research done in the pursuit of vaccines for SARS and MERS coronaviruses established a foundation for SARS-CoV-2 vaccine-development efforts.

Will the coronavirus vaccines work for the common cold?

Don’t bet on it, but you never know. Four different coronaviruses account for about a quarter of common colds; some degree of cross-immunity from SARS-CoV-2 vaccination could be a pleasant surprise. Some scientists speculate that the huge numbers of asymptomatic COVID-19 cases – perhaps as high as 40% of them – may rest on cross-immunity developed by exposure to these common-cold viruses.

I’ve heard there are different types of vaccines for COVID-19. What are they and how do they work?

Some of the first vaccines being tested in clinical trials introduce SARS-CoV-2 spike proteins to the body in a fascinating way. Rather than inject coronavirus spike proteins directly, the vaccines deliver genetic instructions (via messenger RNA, or mRNA) that make their way into shoulder-muscle cells near the injection site. One vaccine now being tested introduces the genetic instructions to muscle cells in a tiny fatty envelope; another vaccine does so using an a weakened common-cold virus called an adenovirus. Once in the muscle cells, the mRNA instructs those cells to produce coronavirus spike proteins that then trigger the immune response.

Other vaccine types used to spur an immune response include DNA vaccines that introduce DNA (rather than the mRNA above) to induce human cells to churn out virus proteins; inactivated and live attenuated vaccines that use inactive or weakened forms of a target virus; and vaccines that directly introduce viral proteins or protein fragments.

What’s a clinical trial? And what are these trial “phases” anyway?

Clinical trials test drugs or medical devices on human beings. To get that far, a vaccine has already shown promise in the laboratory (think petri dishes and test tubes) and in animal studies. Once a vaccine is ready for testing in human volunteers, the U.S Food and Drug Administration (FDA) requires success through three trial phases before approval for widespread use.

A phase 1 trial tests the vaccine’s safety with tens of patients. A phase 2 trials tests the vaccine’s safety as well as its effectiveness at different doses with hundreds of patients. A Phase 3 trial test the vaccine’s safety and effectiveness with thousands of patients. The first vaccines being tested in the U.S. will include 30,000 participants each, and the trials will follow them for two years.

Are you saying we won’t have a vaccine for two years?

Definitely not. Either of these vaccines could prove its mettle in a matter of months, and there are many others in development: the World Health Organization was tracking 165 vaccine candidates as of Aug. 5, of which 26 were in clinical trials and six of those in phase 3 trials. Once satisfied with a vaccine’s safety and effectiveness based on solid preliminary data, the FDA should approve it despite the vaccine’s clinical trial continuing for months or years.

I heard that companies are already manufacturing vaccines. Is that true?

Yes. Moderna, AstraZeneca and others are already producing, or contracting others to produce, mass quantities of vaccines under the assumption that they’ll ultimately be approved. But everything from supplying syringes to managing storage facilities will add to the challenge of the greatest mass-inoculation campaign the world has ever seen.

Who will get vaccines first?

It’s tough to say exactly who will be first in line for the vaccines. The National Institutes of Health has convened an expert group to help determine vaccination priorities. At the moment, it looks like health care and essential workers as well as high-risk populations including older adults, residents of long-term-care facilities, and people with underlying medical conditions will be first up.

Let’s get back to these coronavirus clinical trials. Do all 30,000 patients get the vaccine?

No. These trials are randomized, double-blind, placebo-controlled trials. That’s a fancy way of saying some of the participants get the vaccine and others get a placebo injection of salt water. Who gets drug or placebo will be randomly assigned, and neither the participant nor the health care workers doing the injections will know who gets what. Even the researchers leading the trials will not know whether a given participant has gotten the vaccine or the saline injection. That’s why the trial is known as “double blind”.

Once participants get a vaccine, will researchers intentionally expose them to the SARS-CoV-2 coronavirus?

No. That would not be ethical. Because there are still no effective therapies to prevent someone exposed to COVID-19 from falling seriously ill, intentionally exposing patients to the coronavirus is a no-go. Instead, the idea is to observe the number and severity of naturally occurring infections among the many thousands of volunteer participants who received vaccines or placebos. If there are notably fewer infections – or milder infections – among the vaccinated group, the vaccine is working.

If a vaccine is working, how soon will a person who gets it be protected?

To be determined, but assume at least a couple of weeks. Early results from a phase 1 vaccine trial showed that antibodies only rose to levels similar to those of a recovered patient after the booster shot given a month after the initial injection. But there should be a gradual buildup of immunity during the post-vaccination window.

Will coronavirus vaccines have side effects?

More than half of those receiving early COVID-19 vaccines reported mild, short-term side effects such as fever, headaches, muscle aches, and injection-site reactions.

How long will immunity to COVID-19 last?

No one knows. On the plus side, the coronavirus mutates more slowly than flu viruses, whose viral-protein targets change so fast that annual flu shots are needed. So the coronavirus target isn’t moving nearly as fast. But there’s never been an approved coronavirus vaccine, so it’s not clear either how well these vaccines will prevent COVID-19. Keep in mind, too, that immunity may be partial, as it is with the flu shot. Even those vaccinated could fall ill, but experience lesser – and less-dangerous – symptoms.

Isn’t a vaccine supposed to stop you from getting sick?

Ideally, yes. But vaccines vary in how well they can do that. The measles component of the MMR vaccine is about 97% effective in stopping the measles virus. On the other hand, seasonal flu vaccines’ effectiveness in recent years has ranged from as low as 19% to as high as 60%. Keep in mind, though: even if a vaccine doesn’t stop a virus from setting up shop, it can give the immune system a leg up in battling the invader, resulting in a milder or asymptomatic infection.

Will I need a booster?

Yes, probably. The first vaccines to be tested in the U.S. have required a booster about a month after the first injection.

Why bother with a vaccine if we can just slow-burn until herd immunity?

First, despite alarmingly high infection counts in many parts of the United States, we’re a long way from herd immunity, which happens when enough of a population has developed immunity that a disease’s spread becomes improbable. Herd immunity can happen in two ways: through infection and through vaccination. The herd-immunity threshold is unknown with the coronavirus, but it’s thought to be somewhere around 43% to 66% of the population.

Even if we were to assume 10 times more U.S. infections than the nearly 5 million confirmed cases so far, that’s less than 15% of the U.S. population. Achieving herd immunity by further infecting more about six times the number of people who have already contracted COVID-19 would kill tens of thousands and push the health care system to its limits and beyond.

The very real prospect of effective vaccines being available in a matter of months renders every coronavirus death even more of an avoidable tragedy than has been the case from the beginning of the pandemic. The way forward is to socially distance, clear the air, wash hands, and mask up until a vaccine opens up a controlled, safe road to herd immunity.

About the author

Since 2008, Todd Neff has written hundreds of stories for University of Colorado Hospital and UCHealth. He covered science and the environment for the Daily Camera in Boulder, Colorado, and has taught narrative nonfiction at the University of Colorado. He was a 2007-2008 Ted Scripps Fellowship recipient in Environmental Journalism at CU.

His latest book, "The Laser That’s Changing the World," tells the story of the inventors and innovators who saw, and ultimately realized, the potential of lidar to help solve problems ranging from smokestack-pollution detection, ice-sheet mapping, disaster recovery, and, ultimately, autonomous-vehicle guidance, among many other uses. His first book, "From Jars to the Stars," recounts how Ball Aerospace evolved from an Indiana jar company - and a group of students in a University of Colorado basement - to an organization that managed to blast a sizable crater in the comet 9P/Tempel 1. "Jars" won the Colorado Book Award for History in 2012.

Todd graduated with a business degree from the University of Michigan, where he played soccer, and with a master’s degree from the Fletcher School of Law and Diplomacy at Tufts University. Before becoming a journalist at the turn of the millennium, he was an IT and strategy consultant. He once spoke fluent Japanese and still speaks fluent German.

When not writing, he spends time with teenage daughters and wife Carol, plays soccer, and allows himself to be bullied by a puggle he outweighs by a factor of seven.