How Does the Latest COVID-19 Vaccine Compare to the Others?

Two infectious disease experts at the University of Miami share their insight about the newest COVID-19 inoculation, which requires only a single shot and does not have to be stored at extremely cold temperatures.

Last Saturday the U.S. Food and Drug Administration gave the green light for a third COVID-19 vaccine to join the national rollout. Produced by Janssen and Johnson & Johnson, the newest vaccine is a single-shot dose and does not need to be kept at sub-zero temperatures, which should make it easier to distribute. However, the vaccine also has slightly lower rates of effectiveness.

The University of Miami Miller School of Medicine’s infectious disease experts have been following the vaccine rollout closely. The Miller School is serving as a host site for national clinical trials on two out of the three vaccines now in use—the Moderna and Janssen products. Although inoculations for these studies ended in 2020, the full trials last two years and University researchers will follow patients until 2022.

Dr. Susanne Doblecki-Lewis is the University’s lead investigator for the Moderna trial. She is a professor of medicine and clinical director in the Division of Infectious Diseases, as well as the University’s medical lead on its COVID-19 vaccine task force.

Dr. Dushyantha Jayaweera is the University’s lead investigator for the Janssen trial. He is a professor of medicine in the Division of Infectious Diseases and is associate director of the Miami Clinical and Translational Science Institute.

The two physicians provided some details about the new vaccine and what it means for the nation’s vaccine distribution efforts.

Many physicians have said that the Janssen vaccine works differently than the strategy used by Pfizer and Moderna vaccines to fend off COVID-19. Can you explain how it is different? 

Jayaweera: The existing Pfizer and Moderna vaccines use what’s called messenger RNA (mRNA) to alert the body’s cells and simulate a COVID-19 infection. The presence of this COVID-19 mRNA prompts the body to produce antibodies against the novel coronavirus.

On the other hand, the Janssen vaccine uses inactive particles of a cold virus (called adenovirus), which contain COVID-19 spike protein DNA within them. 

When the Janssen vaccine is injected into a person, these adenovirus particles attach to the surface of human cells and enter the nucleus. Within the nucleus, the DNA of the COVID-19 spike protein is identified, which prompts the cells to produce mRNA. This mRNA then signals the cell to make spike proteins, which the body’s immune system will identify and then make antibodies to fight off COVID-19 if the person is exposed to it in the future.

An advantage of the Janssen vaccine is that it uses DNA that is stable compared to messenger RNA, which are more unstable and break down. Therefore, the Janssen vaccine does not need deep freezing like the Moderna and Pfizer vaccines require. And the distribution of this vaccine across the world is much easier than the other two.

Overall, these are two different mechanisms for developing vaccines, but both are very effective for warding off severe COVID-19 infection.

Since this vaccine is one dose, does that mean the potential side effects could be stronger with this one? Are there any reported side effects from the trials? 

Doblecki-Lewis: The side effects are similar to the side effects reported with the other vaccines—mostly some soreness at the site of injection and some general body aches, fatigue, and malaise are fairly common.

It has been reported that the Janssen vaccine is 66 percent effective overall and 72 percent effective in the United States, compared to the Pfizer and Moderna vaccines, which are in the 90 percent range. Why do you think this vaccine is less effective? 

Jayaweera: You can’t compare one to the other because the populations of the clinical trials were different. It is possible that when the Moderna and Pfizer trials were done, it was early on in the pandemic and did not have that many variants in the study population.   

Doblecki-Lewis: There was a lot more COVID-19 circulating, and more variant strains, when the Janssen vaccine was tested. So, it is important not to get too focused on a specific number. We know that all three vaccines work well, and importantly, protect extremely well against critical illness and death. Ultimately, we want vaccines that save lives, and all three of the available vaccines do this very well.

Is there any information about how well this new vaccine protects people from the COVID-19 variants?  

Doblecki-Lewis: This is difficult to answer because the variants are changing all the time, and the vaccines were not tested under the same conditions. The most reassuring information is that even in South Africa, where most of the infections were with a variant of the virus, the Janssen vaccine provided excellent protection from critical illness and death.

Jayaweera: This vaccine is still under an ongoing two-year clinical trial in the United States, Brazil, and South Africa. Its emergency use approval is based on preliminary results, which showed that it is 85 percent effective at preventing severe disease four weeks after vaccination. Since some of these preliminary clinical results occurred in South Africa, we know there is some protection against the B.1.351 South African variant. But we still know very little about how much protection. That will take more time to decipher.

Since the Janssen vaccine is one dose and does not have to be stored at such cold temperatures compared to the others, do you think this will help with its distribution, or people’s willingness to take it?

Doblecki-Lewis: Yes. The single-dose regimen and easier transportation and storage are a huge advantage for this vaccine compared to the others. It simplifies the process a lot.

What would you say to people who are considering getting vaccinated, but do not want to get this new one because it’s less effective?

Doblecki-Lewis: It is much better to get an effective vaccine now than to wait. All three vaccines are safe and highly effective in preventing severe disease and death. Every day, there are tens of thousands of new COVID-19 infections in the United States and thousands of deaths. I strongly recommend that anyone who is offered a vaccine accept the one that is offered first. That is the best strategy, both for the individual and for public health. Sooner is better than later.

Doblecki-Lewis: The next emergency use authorization submissions will probably be from AstraZeneca and Novavax.

Do you think that having a third COVID-19 vaccine option will help accelerate the ability of young adults and children to get vaccinated? 

Doblecki-Lewis: Yes. More options are important and will accelerate the efforts to make vaccines widely available.

Experts also noted that when it comes to getting vaccines, people with cancer (or with a history of cancer) can get some of the COVID-19 vaccines, but this depends on many factors—such as the type of vaccine, the type of cancer a person has (or has had), if they are still being treated for cancer, and if their immune system is working properly. Therefore, it is best to speak with your doctor before getting any type of vaccine. 

By Janette Neuwahl Tannen

Published on March 3, 2021