Moderna pushes ‘half dosing’ of COVID vaccine, but is it safe? Doctor weighs in

INDIANAPOLIS (WISH) — Moderna is in talks with the Food and Drug Administration (FDA) to emergency authorize “half dosing” of the coronavirus vaccine for the public.

This is an effort to stretch supply and give double the number of people immunity to COVID-19. 

Indiana State Department of Health on Friday reported 69 more Hoosier deaths, for a total of 8,251. A total of 552,594 Hoosiers have tested positive for COVID-19.

News 8 asked Dr. Kurt Kroenke, researcher at the Regenstrief Institute, to weigh in on the proposal. 

Gillis: Moderna is considering rolling out their vaccine, but only giving half the dose to the public. The FDA isn’t sure if it’s a good idea or not. What are your thoughts about this effort to stretch the supply?

Kroenke: Well, I think there is always sort of a tension between when you have an urgent crisis versus the more conservative approach the FDA takes. I think the FDA has been expediting things all along. I think the half dose is only part of the solution. Part of the problem we have now is getting the doses out there because most of this is at the state level. There are things like “Do we have enough people at the site? At the clinics? Are the syringes and needles adequate?”…things like that. So, part of it is logistics right now. 

It’s been estimated that we have 185 million doses to cover us between now and June, but only 5 million people have been vaccinated. But I think giving half doses would probably work through the spring. The studies they’ve done said they would get as much as an immune response with a half dose as much as they would with a full dose. 

But in the big trials they used the full dose and that’s where we found it was 94% effective. So, I would say if we needed to use a half a dose to make it stretch I think that would be fine through this spring. 

Gillis: Speaking to the studies you were talking about. They had to figure out that kind of sweet spot. But when it was a lower dose it was still effective. 

Kroenke: Yes. It was effective in terms of the immune response. So, they would measure in a person’s blood the immune response and that was a study with somewhere around 1,000 patients. But when they did the big trial–the 30,000 patients–they gave the full dose because the full dose was safe and a lot of times we err on the side of “Let’s give extra just to be sure.”

The big trials were done with the full dose. That’s where we have the greatest confidence. I think that’s what we would use in the future. But if there is a shortage this spring to get to the critical populations I think going with a half dose would not be a wrong approach.  

Gillis: And what would this do to the time intervals between doses should the FDA approve this? How might the timing be affected because we really only have a short window–maybe one to two days. Whereas with other vaccines we might have a little more flexibility.    

Kroenke: Whether they give the half dose or the full dose with the current vaccine, it would still be two doses. We’d just give half the dose. The fact that you have to give two doses already creates a time-lag between when people are fully immune. So, if they are going to do this sooner rather than wait until May…but there is another vaccine that’s coming out that is a single dose. But that has not yet been approved. 

So, my guess is we will be in better shape six months from now for the next season. I think for next season though we will have to make some compromised decisions like policy makers are doing. 

Gillis: You just cut out for a second in terms of how the timing might be affected. The 21 days versus the 28 days for the first doses and weeks later for the second dose. Could you say that one more time? 

Kroenke: To my understanding is that the time intervals wouldn’t change, just the dose would change. So, there still would be the several week period between doses. You’d cover twice as many people with half a dose. 

Gillis: And final thoughts on this.

Kroenke: I do think this is a very important issue, but the population really affected by far are the people they are targeting first, which is people over 70. I mean, if you’re a kid or a young adult your risk of having a really bad outcome to the disease is very low. So, I think prioritization of older adults and people in long-term care facilities and then maybe people with medical conditions. But that’s less than half the population. So, I think for this spring it’s probably safe for us if we didn’t have enough vaccines to cover younger people and so forth, they are going to do fine because of the risk…they might get sick if they get it, but in most cases they are not going to have a bad outcome. 

News 8’s medical reporter, Dr. Mary Elizabeth Gillis, D.Ed., is a classically trained medical physiologist and biobehavioral research scientist. She has been a health, medical and science reporter for over 5 years. Her work has been featured in national media outlets. You can follow her on Facebook @DrMaryGillis.