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Ask an Infectious Disease Expert: What Can We Expect From a COVID-19 Vaccine?

ask an expert

Makeda Robinson, MD, Ph.D., is an infectious disease specialist currently studying virus-host interactions in emerging viruses at Stanford University. Each week, Dr. Robinson breaks down complicated COVID-19 topics and addresses pressing public health concerns.

As researchers around the world race to create a vaccine for SARS-CoV-2—the virus that causes COVID-19—there are growing concerns over the potential side effects, distribution, and accessibility of a vaccine.

A Gallup poll in August found that one in three Americans said that they would not receive a COVID-19 vaccine.

There are several ongoing global trials that have enlisted thousands of volunteers to test potential vaccines. Many candidates are already in the last phase of trials—but what happens if a vaccine is developed and no one wants to take it?

Dr. Robinson spoke to Verywell Health to quell vaccine fears, elucidate what goes on inside these trials, and explain the important role vaccines will play in ending the COVID-19 pandemic.

Verywell Health: Can you explain why a vaccine is so important for a virus like SARS-CoV-2?

Dr. Robinson: The development and distribution of vaccines have been one of the largest contributors to improvements in public health in the last century. The number of lives they have saved and improved is tremendous. In the U.S. alone, the Centers for Disease Control (CDC) estimated that in 2014, vaccinations prevented 21 million hospitalizations and 732,000 deaths in children born in the last 20 years.

Even if a virus does not prove to be fatal, there are potential long-term sequelae of infection. We are now seeing this phenomenon with the COVID-19 long-haulers, a group of people who have recuperated from the acute infection only to live with chronic, life-altering symptoms. 

While we know that masks, social distancing, and hand hygiene practices are effective, if you're anxious for life to go back to “normal,” the fastest and most efficacious way to do that is going to be through a vaccine(s).

We are still learning about how protective our natural immunity is. Even in the hardest-hit cities in the U.S. such as New York City, it is estimated that 20% of the population has been infected, with the estimated herd immunity threshold closer to 70%.

Our best approach to bridge this gap without continued loss of life is vaccination. This is why it's so important that the safety profiles of these vaccines are being studied fully and we don’t put the cart before the horse. The collaborative efforts between government, industry, and academia have led to rapid progress, and while it’s important not to lose time, going “slow” now is the fastest option to gauge responses to vaccination and build vaccine confidence. 

Verywell Health: What’s something important that people need to know about the vaccine development process right now? 

Dr. Robinson: Right now, we are all getting a front-row seat to the scientific process. It can at times seem as though scientists already have all the answers, but those answers come from experimentation and validation. We’re now going through the entire process under a microscope.

The development of a vaccine isn't always a straightforward process, which is why vaccines traditionally can take decades to be approved. The clinical trial phases are the common pathway used for vaccinations or other therapeutics on the market today. They've been sped up to “warp speed” during the pandemic.

Each vaccine trial has a data safety review board (DSRB) which is an independent arm of the clinical trial. They meet periodically to look at the data in real-time and make decisions about whether it is safe to continue the study, allowing those running the studies to be blind to the outcomes and prevent biased analysis of the results.

However, it's incredibly important for people running these studies to be as transparent as possible to engender confidence and trust. Recent polls have found that potentially 30-50% of Americans would be hesitant to receive a COVID-19 vaccination. Without a higher population, buy-in technology will be irrelevant.

Verywell Health: How many vaccine trials are currently underway for SARS-CoV-2? When do you think a vaccine will be ready?

Dr. Robinson: There are no vaccines that have been approved for full use. There are 44 vaccine candidates in human clinical trials with five approved for limited use, and 11 in Phase 3 clinical trials. The majority of these vaccine platforms are either adenoviral vectors, mRNA-based vaccines, or inactivated virus vaccines.

The diversity of these vaccine candidates is crucially important to prevent us from putting all of our eggs in one basket. Having this many options in the pipeline will give us the best chances for implementing a concerted vaccination effort starting in 2021. 

Verywell Health: One potential vaccine, AstraZeneca, was put on a brief pause but is now back on track. Is it normal for vaccine trials to go on pause? 

Dr. Robinson: When working on this scale of tens of thousands of participants, the potential for someone to develop an illness unrelated to the vaccine begins to increase. When an adverse event occurs, the investigation of the underlying cause is crucial.

Regarding the AstraZeneca trial, there was an initial pause in July after a patient developed neurologic symptoms later determined to be caused by multiple sclerosis and deemed unrelated to the trial.

The second, most recent pause was due to a woman in the U.K. who developed a neurologic condition consistent with transverse myelitis, an inflammatory process involving the spinal column. She received the vaccine and not the placebo.

While the trial remains on pause in the U.S. as the FDA explores the incident further, it has been restarted in other countries, and we will have to continue to monitor the outcomes. This is a prime example of why we should not race forward with an incompletely tested vaccine to be available for man-made deadlines.

Verywell Health: Why is it important to distribute a vaccine equitably, and what measures are being taken to do that? 

Dr. Robinson: The World Health Organization (WHO) has been working to put together an organization that will facilitate equitable global access to vaccines. Their goal is to deliver 2 billion doses of a safe vaccine by the end of 2021. It's a collaborative model and it shows the strength of an institution like the WHO at a time like this to prevent disparities in access. Those who are participating in this consortium will receive a sufficient number of vaccinations to cover at least 20% of their population. 

There are nine vaccines in the WHO portfolio, including the Moderna and AstraZeneca vaccines. As more vaccines move through the pipeline, the challenge of developing the structures necessary to deliver, store, and administer the vaccinations appropriately will become a priority. Both ethically and logistically, it is crucial that we have an equitable distribution of vaccines for the global reopening, which will require strong leadership and collaboration. 

Verywell Health: Why is it important for everyone who is physically able to get a vaccine to receive one in order to protect those who can't?

Dr. Robinson: There is a subset of people whose immune systems can't mount a robust response to a vaccine. They are incredibly vulnerable during this time, and they've had to take COVID-19 precautions even more seriously as their lives more acutely depend on them. I think the more we can put ourselves in their shoes, the easier a decision it is to be cautious and respectful of the people around us and to see the ability to be vaccinated as an opportunity not available to everyone. 

Verywell Health: Can you talk about the potential of antibody-dependent enhancement with vaccines? 

Dr. Robinson: The idea here is that when you make antibodies to a virus, either through natural infection or vaccination, some of the antibodies will work better than others. Those that are less potent may be able to recognize the virus but unable to neutralize it. This can lead to complexes of virus and, potentially, an increased inflammatory response.

There were some concerns for antibody-dependent enhancement with the development of other vaccines to coronaviruses. While this is an important consideration, we will need to continue to mine information from re-infection cases and vaccine clinical trials to better understand if this is occurring with SARS-CoV-2. 

Verywell Health: What's the worst side effect that could occur from a COVID-19 vaccine?

Dr. Robinson: Common vaccine side effects include fever, fatigue, and pain at the site of injection. These symptoms can occur with any vaccine. Going beyond these general risks, specific adverse effects are variable based on the specific vaccine.

Many of the current late-stage vaccines are adenoviral vector vaccines, similar in structure to the AstraZeneca vaccine. We are still waiting to get further details about the episode which halted this study in order to better assess the underlying cause. Based on the information that has been shared, it seems the patient has recovered and it is unclear if the episode was linked to vaccination.

A worst-case scenario would be that for a subset of those vaccinated, symptoms of transverse myelitis such as muscle weakness or paralysis would not be completely reversible. However, we should also remember that there are risks to natural infection with SARS-CoV-2, which has been linked to neurologic syndromes such as transverse myelitis. 

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  1. O’Keefe SM. One in three Americans would not get a COVID-19 vaccine. Updated August 7, 2020.

  2. The Centers for Disease Control and Prevention (CDC). Report shows 20-year US immunization program spares millions of children from diseases. Updated April 24, 2014.

  3. American Association for the Advancement of Science (AAAS), Science. Just 50% of Americans plan to get a COVID-19 vaccine. Here’s how to win over the rest. Updated June 30, 2020.