With Two COVID-19 Vaccines on the Way, “We Are in New Territory” (Interview w/ Drs. Corley & Douam)

A week after Pfizer caused excitement by announcing that its coronavirus vaccine has been more than 90 percent effective in early trials, Moderna came out with its own announcement that its version of a coronavirus vaccine had reached more than 94 percent effectiveness.

Anthony Fauci (Hon.’18), director of the National Institute of Allergy and Infectious Diseases, called Moderna’s early results “stunningly impressive,” and the stock market rallied as investors took it as a sign that there may soon be powerful new public health tools to control the sprawling pandemic.

Like the Pfizer vaccine, the Moderna vaccine is developed using mRNA, which stands for messenger RNA. This single strand of genetic information is “read” by biological machinery inside cells, acting like an instruction manual that directs the cell to build proteins of certain specifications. The coronavirus, once it has infected a cell, uses mRNA to trick the cell into manufacturing more copies of the virus. But Pfizer and Moderna are using mRNA to tell the cell how to build proteins that resemble the SARS-CoV-2 virus that causes COVID-19 infections, similar enough to impart immunity on a vaccinated person, but not cause an infection.

With two vaccines now racing toward US Food and Drug Administration approval, The Brink reached out to Ronald Corley, director of BU’s National Emerging Infectious Diseases Laboratories (NEIDL) and a BU School of Medicine professor, and NEIDL virologist and vaccine expert Florian Douam, a MED assistant professor, to get their takes on how the Pfizer and Moderna vaccines could change the course of the pandemic.

The Brink: The Pfizer and Moderna vaccines sound like very similar formulations. How do these mRNA vaccines work compared to other popular vaccines (flu, measles/mumps/rubella, etc.)?

Corley: mRNA vaccines are designed to deliver mRNA, encoding a particular component of the virus into the host’s cells, which then make the protein encoded by the mRNA. The person being vaccinated then makes an immune response to these proteins. Other forms of vaccines generally have the already-made proteins in their formulations, and deliver them with other components (vectors and adjuvants) that are designed to boost the immune response to the viral proteins. 

Why is the mRNA approach well-suited to prevent coronavirus?

Corley: There are a number of potential advantages to mRNA vaccines: they can be more readily optimized, they can be administered repeatedly, and they might be more scalable over time. Yet, we are in new territory until we know more. It is unclear whether the mRNA vaccines will be better than other conventional vaccines at this time. There remain many unknowns: are the vaccines similarly effective across demographic lines (age, sex, ethnicity, etc.), do they prevent disease (in both trial groups, vaccinated persons did get infected, but many fewer than in the placebo goups), and how long does immunity last? 

Douam: I would not say that mRNA vaccines are particularly well-suited for coronavirus, specifically. They can be suited to prevent any infection. The advantage of mRNA vaccines over other types is 1) they are easy to make and can be made faster than a lot of other vaccines and 2) their safety. That being said, mRNA vaccines are likely to [induce less of an immune response] than other types of vaccines, like live-attenuated vaccines or viral vector-based vaccines (like the Johnson & Johnson adenovirus-based COVID-19 vaccine), but because we can produce a lot [of mRNA COVID-19 vaccines] faster than these other types of vaccines, this is why the mRNA vaccines are leading the race right now.