Coronavirus vaccines 101: What you need to know

Dec. 23, 2020
nurse with mask and shield readies a coronavirus vaccine for a patient wearing a mask.
Vaccines to prevent COVID-19 are safe and effective, according to the FDA. Photo: Getty Images.

Editor’s note: For the most up-to-date COVID-19 vaccine information, please click here.

Coronavirus vaccines have arrived and they’re highly effective in protecting people from COVID-19.

To help you understand more about vaccines for COVID-19, we consulted with UCHealth vaccine experts including Dr. Thomas Campbell, Dr. Michelle Barron and Dr. Richard Zane.

What is a vaccine?

Vaccines train our body’s immune system to recognize and attack pathogens. Think of a vaccine as a tool that kicks your immune system into gear and warns it to get ready for an invader. Vaccines give the body a sneak peek of one or more key features of a virus before the actual virus barges in. The immune system then develops a “memory” of a virus and can fight it the next time the virus tries to invade. Once you are protected, you have what are known as antibodies.

Humans have been subject to pandemics for centuries, and in the last 100 years or so, vaccines have been the tool that have helped us control, or in some cases, eliminate the pathogens that allow viruses to make us sick. (To learn all about viruses, click here. To learn more about vaccines at UCHealth, click here.)

Are COVID-19 vaccines safe?

Yes. In order to be approved, vaccine makers must prove to the U.S. Food and Drug Administration (FDA) that vaccines for COVID-19 are both safe and effective.

“The COVID-19 vaccines have been tested successfully on tens of thousands of people through clinical trials,” said Dr. Richard Zane, executive director of emergency services for UCHealth and UCHealth’s chief innovation officer.

Furthermore, said Zane, independent scientists have reviewed the COVID-19 vaccine trial results to make sure they are safe.

Researchers will continue to study long-term safety of COVID-19 vaccines, said Dr. Thomas Campbell, who is running the clinical trial for the Moderna COVID-19 vaccine at UCHealth University of Colorado Hospital on the Anschutz Medical Campus.

Added Thomas: “The vaccines have been successfully tested in clinical trials on tens of thousands of people.”

Do vaccines work?

Yes, vaccines have been very effective. Consider small pox, for example. “We were able to eliminate small pox from the face of the earth,” Campbell said.

We also have very effective vaccines now for other diseases that used to have a very big toll such as yellow fever, measles and chicken pox.

Do the vaccines for COVID-19 keep you from getting sick?

Yes. Says Campbell: “We have early results on the effectiveness for both the Moderna and Pfizer vaccines, which are very encouraging. Both have 94-to-95% efficacy, which puts them at the highest category of vaccines, like the measles vaccine. This is very, very encouraging.”

Dr. Richard Zane receives his COVID-19 vaccine.
Dr. Richard Zane was thrilled to receive his first dose of a remarkable new COVID-19 vaccine. Photo by Katie McCrimmon.

What is a clinical trial?

“Clinical trials are very well-controlled, tightly-designed experiments where efficacy (or how well a vaccine works) is determined,” Campbell said. “Efficacy is measured in terms of reduction in disease, relative to a placebo. These are all placebo-controlled, randomized and blinded (experiments). We can compare what happens to people who get the vaccine and what happens to people who get the placebo.”

What does “efficacy” mean?

Efficacy describes how well a vaccine works. “Vaccines are measured in terms of how much they can reduce the risk of getting symptomatic with COVID-19 illness. We don’t know yet if these vaccines will reduce infections and reduce transmissions. But, we do know that they reduce illness, and that’s very, very important,” Campbell said.

What is a placebo?

A placebo is any substance that appears to be real, but is not. When researchers do clinical trials to see how well a vaccine works, they must give some participants the real vaccine and others a placebo. Then, the researchers see how well both sets of patients do. For the COVID-19 vaccine trials, the placebos were made from salt water, which is harmless to our bodies.

What are “double blind” clinical trials?

Double blind means that neither the doctor nor the clinical trial participant knows who receives the real vaccine and who receives the placebo. The concept of a “double blind” trial is important because both participants and researchers could be biased if they knew who received the real vaccine.

Why are vaccines so important now?

Some people are getting very sick and are dying from COVID-19 because our bodies don’t have any immunities to this new virus. Humans had never been exposed to the virus that causes COVID-19 until the virus jumped from animals to humans in late 2019. Vaccines are vital for saving lives and for reducing the burden on health care workers

Are there side-effects for the COVID-19 vaccines?

Some people said the vaccines didn’t hurt and they had no side-effects. Others reported minor side-effects. For most people, these are easy to handle, Zane said. They can include soreness in the arm, just like when you get a flu shot. Some people also might have some body aches and a low fever, particularly after receiving a booster dose. But, these relatively minor side-effects are not even comparable to the potential health problem that a serious case of COVID-19 can cause, Zane said.

How can I stay safe until I get a vaccine?

Keep being vigilant. It will take time to get everyone fully vaccinated. Until then, people need to keep being very careful. “The basics still apply: wearing masks when you’re out and about, making sure you are washing hands and trying to avoid large gatherings,” Campbell said.

Will I need a booster shot?

Yes. Booster shots will be required for the COVID-19 vaccines that have been approved so far. Infectious disease expert, Dr. Michelle Barron, said it’s important for people who receive a vaccine to continue protecting themselves.

“There are two shots for several of these vaccines. Once you get your first shot, you’re not done. That does not give you permission not to follow the rules, like masking, social distancing and hand-washing.”

Also, it can take some time for a shot to become fully effective, even after the second booster dose.

“A flu shot takes about two weeks to be effective,” Barron said.

How long will immunities last?

Campbell said researchers don’t yet know how long the immunities will last, but say that is not a critical issue since people can always get additional booster shots if immunities decrease over time.

“The vaccines produce a high level of antibodies against the SARS-CoV-2 virus (the virus that causes COVID-19) and these antibodies decline slightly over the first four months or so. We don’t know what happens to the protection (over time). We will continue to study that. But, I don’t view that as an Achilles heel (of the vaccines) by any means,” Campbell said. “We can always give a booster at a later time if immunity declines.”

If I get a COVID-19 vaccine, can I still get COVID-19?

Experts say it’s still possible for a small fraction of people to get COVID-19 even if they have had a vaccine. “But, if you get COVID-19 after getting your vaccines, which is unlikely, your symptoms will be dramatically less severe, meaning you are far less likely to need medical care,” Zane said.

Should people who have had COVID-19 still get a vaccine?

Yes. People who have had COVID-19 should still get a vaccine because experts are not certain yet how long the antibodies to the virus last. Also, there are some documented cases of people who have gotten COVID-19 twice.

Can cancer patients receive the COVID-19 vaccine?

The vaccine trials did not exclude people with cancer, but they did exclude people who currently are taking immunosuppressing medications. “We don’t know if the vaccines will work in these groups. There’s no information (yet) that they won’t be safe for people with cancer,” Campbell said.

Are the vaccines safe for people with diabetes?

“We know the vaccine is safe and works well for diabetics,” Campbell said. Many of the vaccine trial participants had diabetes and they did well.

Are the vaccines safe for people with lupus and multiple sclerosis (MS)?

People with lupus or MS were not excluded from the vaccine trails unless they were currently taking immunosuppressive drugs.

Are COVID-19 vaccines safe for children?

Vaccine trials for children are under way now. So, children will not be the first to receive vaccines. So far, the vaccines have not been approved for children under age 16. Results on vaccine trials in children will not be available until 2021.

Should infants and children keep getting other vaccines?

Yes. Health experts are very concerned about the danger of other outbreaks of other vaccine preventable diseases if parents stop taking babies and children in for their regular check-ups and immunization appointments.

“We don’t want to end up with a measles outbreak,” Barron said. She strongly urges parents to be vigilant about taking their children to medical appointments.

“Medical checkups can be done safely. We have many checks and balances to keep people safe. Don’t delay,” Barron said.

How soon does protection start after you get a vaccine?

The vaccines start protecting people quickly. “Within five to seven days after the first injection, you will have partial resistance to COVID-19. Within five to seven days after the second shot, it will be about 94-to-95% effective,” Zane said.

Do the vaccines work well on people of various ages, races and weights?

Yes. The vaccines worked well on adults of all ages, races and weights.

I’ve heard the Pfizer and Moderna vaccines are a new type of vaccine. What does that mean and are the new mRNA vaccines safe?

These vaccines are a new type, but they are safe, and have been in development for about 20 years, Zane said. The Pfizer and Moderna vaccines use what is called messenger RNA or mRNA to deliver instructions to the muscle cells in our arm to start producing a protein which is substantially similar to a protein on the COVID-19 virus; the spike protein, which prompts our bodies to make antibodies for COVID-19. We already have mRNA in our bodies, and soon after the mRNA does its job, it disappears. “It’s like you own cells become temporary vaccine producers. These vaccines are incredibly cool and will define how we combat future pandemics,” Zane says.

How exactly do vaccines for the new coronavirus vaccines work?

The Pfizer and Moderna vaccines 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 from getting into cells, replicating itself and making a person sick.

After I get a vaccine, do I still need to wear a mask?

Yes, it will take time to get enough people vaccinated to reduce infections of SARS-CoV2, the virus that causes COVID-19.

“Even if you get vaccinated, you must continue to keep being vigilant, wear masks in public, wash your hands frequently and avoid close contact with people outside of your home,” Zane said.

Will the coronavirus vaccines work for the common cold?

It’s possible, but not likely. 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 introduces the genetic instructions to muscle cells in a tiny fatty envelope; another vaccine does so using 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.

In the clinical trials, what are the “phases”?

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 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.

How did scientists know that the vaccine clinical trials worked?

If the Pfizer and Moderna vaccines were as biologically neutral as the salt water that people in the placebo groups received, approximately half the COVID-19 cases would have been in the vaccine group and half in the placebo group. When the count was complete, both trials found that, on average, more than nine in 10 participants who came down with COVID-19 had gotten the salt water shots and not the vaccine. That’s an effective vaccine. What’s more, the Moderna trial found that, of 30 volunteers who became infected and developed severe cases of COVID-19, all had received the placebo.

How did researchers start creating the vaccines?

On Jan. 10, 2020, Chinese scientists published the SARS-CoV-2 virus’s genetic sequence a mere month after the first publicly recorded case of a strange flu in Wuhan, China. Just two days later, scientists at Moderna and the National Institutes of Health had zeroed in on a coronavirus vaccine target.

How were scientists able to learn this information and develop vaccines so quickly?

Decades of work by countless researchers has brought incremental advance after incremental advance to our understanding of how viruses and the cells they infect work. Biochemists, virologists, microbiologists, bioengineers, chemical engineers, electrical engineers, mechanical engineers, computer scientists and others have developed ways to decode a stretch of DNA or RNA and know with astonishing certainty what sort of protein a cell’s ribosomes will crank out when fed that genetic sequence.

What was the previous record for developing a vaccine?

The previous record for developing a vaccine was four years for mumps, in 1967.