Your guide to a COVID-19 vaccine: What the public needs to know

Keck Medicine of USC

News about a potential COVID-19 vaccine is announced almost daily, leading people to wonder when will a vaccine will be available, and whether it will be safe. Edward Jones-Lopez, MD, MS, a Keck Medicine of USC infectious diseases expert and investigator of one of the Operation Warp Speed vaccine clinical trials, answers the questions on everyone’s mind.

How many potential COVID-19 vaccines are there?

Currently there are some 45 vaccine candidates testing in human clinical trials in addition to many being tested in animals. Researchers are using a wide variety of approaches to potentially stimulate an immune response in the body to protect against SARS-CoV-2, the virus that causes COVID-19. The most common type of vaccine candidate contains a virus that has been genetically engineered with coronavirus genes to provoke the intended immune response. 

Can you explain the different phases of COVID-19 vaccine clinical trials?

After initial laboratory and animal testing is completed, vaccine candidates enter a phase 1 human clinical trial, where a small group of people (10-50) receive the trial vaccine to determine the dosing of a potential vaccine, potential side effects of the administration of the vaccine and safety of the vaccine. Phase 2 expands to hundreds of volunteers where we continue to test a vaccine for safety and collect early data about the vaccine’s potential efficacy.

In phase 3, the trial expands to tens of thousands of people to measure if the vaccine offers protection against SARS-CoV-2 infection or severe disease, and to continue to focus on safety in a diverse population. In the United States, the Food and Drug Administration (FDA) will approve a COVID-19 vaccine only after a successful phase 3 trial. Several potential COVID-19 vaccines are currently in phase 3 clinical trials, each including 30,000 or more volunteers.

How do Phase 3 clinical trials for potential COVID-19 vaccines work?

In these trials, one group of volunteers is randomly selected to receive the experimental vaccine, while another receives the placebo. Researchers then compare how many of those who were vaccinated become infected or ill with the coronavirus versus those who received a placebo. The FDA has determined that a COVID-19 vaccine must be at least 50% effective in preventing COVID-19 or, should someone contract the disease, in protecting against a serious case of COVID-19.

The trials are targeting high-risk-groups more likely to contract the virus or have severe complications to drive outcomes and get quicker results.   

When will a vaccine be available and how effective will it be?

Some phase 3 COVID-19 vaccine clinical trials are getting close to completing the enrollment of volunteers. We could see one or more vaccines become available three to six months after the completion of a trial’s enrollment, which could be as soon as early next year.

It’s likely that people may need to be vaccinated each year, just as for the flu, but we don’t know for sure yet. 

Vaccines typically take five to seven years to be developed.  How is one for COVID-19 being developed so quickly and how can we know it’s safe?

We are benefitting from previous work done over the last decades to find safe, effective vaccines faster. In addition, the manufacturing of a vaccine traditionally begins after the vaccine has been approved through a phase 3 clinical trial. However, given the global emergency related to COVID-19, several state and private entities in the world have agreed to cover the costs of manufacturing millions of doses of potential COVID-19 vaccines during the clinical trials, shaving years off the process.

Despite the speed of development, scientists are adhering to the same rigid safety protocols for a COVID-19 vaccine that have been followed for all other previously approved vaccines and have proven to be safe, in some cases after several decades of use. 

If someone is interested in volunteering for a trial, can they still participate?

Some half a million Americans have signed up to be part of a COVID-19 clinical trial, but more volunteers are needed to complete the trials, including people from high-risk populations and underserved communities. Anyone wishing to volunteer can register at

Editor’s Note: Keck Medicine of USC is involved in an international phase 3 clinical trial for a COVID-19 vaccine sponsored by AstraZeneca and the University of Oxford.


For more information about Keck Medicine of USC, please visit


Filters close

Showing results

110 of 5634
Newswise: shutterstock_1724336896.jpg
Released: 13-May-2021 12:55 PM EDT
Kreuter receives $1.9 million in grants to increase vaccinations in St. Louis
Washington University in St. Louis

Matthew Kreuter, the Kahn Family Professor of Public Health at the Brown School, has received $1.9 million in grants to help increase COVID-19 vaccinations among Blacks in St. Louis City and County.

Released: 13-May-2021 11:35 AM EDT
COVID-19 mRNA Vaccines are Immunogenic in Pregnant and Lactating Women, Including Against Viral Variants
Beth Israel Deaconess Medical Center

In a new study from Beth Israel Deaconess Medical Center researchers evaluated the immunogenicity of COVID-19 mRNA vaccines in pregnant and lactating women who received either the Pfizer or Moderna COVID-19 vaccines. They found that both vaccines triggered immune responses in pregnant and lactating women.

Released: 13-May-2021 10:30 AM EDT
Pandemic stigma: Foreigners, doctors wrongly targeted for COVID-19 spread in India
Monash University

The Indian public blamed foreigners, minority groups and doctors for the rapid spread of COVID-19 across the country during the first wave, due to misinformation, rumour and long-held discriminatory beliefs, according to an international study led by Monash University.

Released: 13-May-2021 9:00 AM EDT
28 Community Programs Receive Grants Through Penn Medicine CAREs Program
Perelman School of Medicine at the University of Pennsylvania

Penn Medicine CAREs awarded grants to 28 projects, many of which aim to fill vast needs in the community created by the COVID-19 pandemic, while others seek to improve diversity, equity, and inclusion.

Released: 13-May-2021 9:00 AM EDT
How to Win Over Vaccine Skeptics: Live Expert Panel for May 20, 3pm ET

How to Win Over Vaccine Skeptics: Live Expert Panel for May 20, 3pm ET

Released: 13-May-2021 8:00 AM EDT
Dental procedures during pandemic are no riskier than a drink of water
Ohio State University

A new study’s findings dispel the misconception that patients and providers are at high risk of catching COVID-19 at the dentist’s office.

Newswise:Video Embedded lung-damage-not-the-culprit-for-post-covid-exercise-limitations
Released: 13-May-2021 7:00 AM EDT
Lung Damage Not the Culprit for Post-COVID Exercise Limitations
American Physiological Society (APS)

A new study suggests the lungs may not be the main factor that reduce exercise ability in people recovering from severe COVID-19. Anemia and muscle dysfunction also play a role. The study is published ahead of print in the Journal of Applied Physiology. It was chosen as an APSselect article for May.

Newswise:Video Embedded australia-accelerates-new-covid-19-vaccine-to-fight-mutant-strains
Released: 13-May-2021 2:05 AM EDT
Australia accelerates new COVID-19 vaccine to fight mutant strains
University of South Australia

A leading South Australian immunologist has been awarded $3 million from the Federal Government to accelerate work on a locally developed Covid-19 vaccine, in what's anticipated to be the second line of defence against the virus.

Released: 12-May-2021 5:10 PM EDT
Understanding SARS-COV-2 proteins is key to improve therapeutic options for COVID-19
Bentham Science Publishers

COVID-19 has had a significant impact since the pandemic was declared by WHO in 2020, with over 3 million deaths and counting, Researchers and medical teams have been hard at work at developing strategies to control the spread of the infection, caused by SARS-COV-2 virus and treat affected patients.

Showing results

110 of 5634