What Should Investors Know About 2-Dose COVID Vaccines?

There is a small amount of data that suggests only one dose of a coronavirus vaccine in a two-dose schedule can provide some protection against the coronavirus. Does this mean that people could safely receive one dose instead of two? Is it too late for investors to start paying attention to companies working on a single-dose vaccine, like Johnson & Johnson (JNJ 0.96%)? Dr. Bruce Gellin of the Sabin Vaccine Institute joined Olivia Zitkus and Corinne Cardina of Fool.com's Healthcare and Cannabis Bureau on a Dec. 18 episode of Fool Live to discuss the two-dose vaccines from Moderna (MRNA -5.90%) and Pfizer (PFE 1.63%)-BioNTech (BNTX 1.87%) team.

Olivia Zitkus: Both of these vaccines are mRNA vaccines, messenger RNA vaccines. While the two mRNA vaccines are intended to be a two-dose regimen, you vaccinate a person and then they return three or four weeks later depending on the vaccine for their second dose, some people are wondering about the potential for just one dose of these mRNA vaccines. Notably an opinion article in the New York Times published just today, I believe this morning, questioned the possibility of getting more people vaccinated by administering just one of the two intended doses. I'm wondering what your thoughts are on this, and what is the impact of these kinds of conversations on the public's behavior?

Dr. Bruce Gellin: It's an important question. I think that part of this is recognizing, I mean there are 300 different approaches that are being taken globally and you probably tracking every one of those, but I think what's interesting is that there's so much interest, so much attention. Any scientist who has an approach to vaccine has come forward, and we're going to learn a lot from that. Not all 300 horses are going to end the race, but I think we're going to learn a lot in that process. But as far as this one and two dose, there are a couple of companies that are focusing on a single dose. I think that's really important when you think about usability. For a program standpoint, finding a person for the first time to get vaccinated is hard enough, getting them to come back when they need to is really a much more complicated challenge which we're going to have to deal with to try to make sure we provide protection. But the question that's really important, what was intriguing, and I think that's probably the best you can say from the data was that both of these mRNA vaccines are two-dose vaccines. The initial clinical trials of phase 1 and phase 2 trials are designed to determine what's the right dose, what's the right dose interval, and it shows that the maximum immune response is after two doses. But because they were looking intensively in these studies, you could follow-up people after that first dose, and you saw that about the two-week mark, 10 days, 14 days, there was a splitting in the curve. What that means is that at about 14 days, some people even after first dose seem to be protected when compared to the placebo. Interesting, encouraging, but very small numbers. While we've seen these what's called a point estimate, when you compare those numbers, it is in the 50-ish percentages, that's intriguing but since there's such small numbers, a confidence limit, as statisticians say is quite wide, and if there was one or two differences in those who is in the placebo group or not, it will be quite different. The short story is until we know a lot more, two doses is what we need, and giving them a first dose could actually cause a difficulty if people don't get the full immunity they need. In doing so, we'll be using a lot of vaccines that might not be protecting the population as we think.

Zitkus: Right, that length of the immunity is still a question with the two-dose vaccine. If we have people just getting one dose of a two dose schedule then that really complicates the data picture.

Gellin: In fact, so looking at the immunology of coronaviruses and other vaccines, we don't expect lifelong protection but maybe we'll be surprised. Given what we know about vaccinology and immune response, a second dose is likely to give a better and longer response.