Top COVID Vaccine Questions Answered

1. There are hundreds of vaccines in development. Can you tell us which ones we should be keeping an eye on? Who are the front-runners?

Currently there are about 40 vaccines listed on the World Health Organization’s DRAFT landscape of COVID-19 candidate vaccines. In the U.S., there are a few top candidates that are in Phase 3 clinical trials or are close to beginning them. There are currently five front runner vaccines in the Phase 3 clinical trials in the US:

1. Moderna has a mRNA vaccine
2. Pfizer has a mRNA vaccine
3. AztraZeneca has an adenoviral vector vaccine
4. Sinovac has an inactivated vaccine
5. Johnson and Johnson have an adenoviral vector vaccine

2. What are the major differences in the vaccines that are being created?

Most of the vaccines differ in the vaccine platforms from which they are made, although some have the same platform but different constructs. Interestingly, several of these vaccines utilize vaccine platforms that are new to vaccines, in general. The mRNA vaccines are based on a new technology that has not been used as an FDA-approved vaccine before and are based on nucleic acids, like DNA and RNA. There are also inactivated adenoviral vector vaccines. These vaccines use a non-replicating virus called adenovirus as a vehicle to immunize us with a small piece of non-infectious SARS-CoV-2. Although these vaccines also have yet to be used as an FDA-approved vaccine, they have been tested in early phase trials with the Ebola vaccine. Inactivated vaccines have been treated so that they don’t replicate or make copies of themselves and are usually just pieces of the virus that do not grow. Inactivated and subunit vaccines involve platforms that have been used in the past, however, with new viruses these platforms types still need to go through the phases of clinical trials to ensure safety, immunogenicity and efficacy. Immunogenicity means that the vaccine is able to induce a good immune response against the virus, which helps us with protection and recovery. Another difference in these vaccines is that many require two injections of the vaccine that are spaced out by a few weeks to a month. In contrast to most of these top vaccine candidates, the Johnson and Johnson vaccine involves only a single injection. 

3. Why was the AstraZeneca trial put on hold? Is this something we should be very concerned about?

The AstraZeneca vaccine, an adenoviral vector vaccine, was put on hold in both the U.S. and the U.K. when a participant in the U.K. trial developed transverse myelitis, or inflammation of the spinal cord. With the identification of a serious adverse event, any clinical trial will pause and investigate safety concerns. In this case, the trial resumed about a week later in the U.K. following investigation, but the trials in the U.S. are stilled paused and the investigation is still ongoing. At this point, given that the U.S. trials are still investigating, it is too early to say for sure if this type of reaction is something to worry about.

4. A vaccine made in a year is unheard of. Should people be worried that a vaccine is being created too quickly?

Review and FDA approval of a new, safe, and effective vaccine for a new virus in a year is a huge scientific and medical achievement. Although such a process is new, it can be helpful to put this in context with the current global public health landscape, which is also something very new and concerning. A safe and effective vaccine is needed. Although several of the vaccines currently in Phase 3 clinical trials involve new platforms, several of the platforms have been investigated for other pathogens such as Ebola as well as other SARS viruses such as MERS-CoV (the viral cause of Middle East Respiratory Syndrome). With the discovery of SARS-CoV-2, the current viral cause of COVID-19 and the quick publication of the viral genome sequence, many of these already existing technologies were quickly modified and tested in pre-clinical studies with very promising results. This really helped meet the requirements for FDA approval to initiate clinical trial phases. Another point to consider is the financial support that has been allocated so quickly to the science and medical review for these needed vaccines, which is something not typical for vaccine development. With the development and review of any new vaccine or therapy, safety and efficacy are necessary. These vaccine characteristics are what we need to watch for as this data continues to become available throughout the next months.   

5. Will a vaccine mean life can return to normal? How effective do we think a vaccine will be? 

This is a very tough question to answer. A vaccine will hopefully benefit many, especially those who are high-risk for severe COVID-19 disease or complications associated with SARS-CoV-2 infections. At this point, we are still waiting to see the data on how effective the current vaccines are in preventing infection and/or preventing disease. Most data so far show that the vaccines induce virus-specific immune markers and/or responses that are comparable, some even greater, then what we see in patients who have recovered from infection. Although this data is promising, we do need to wait and see what the efficacy data is from Phase 3 clinical trials.