As the United States surpasses the half-million mark in deaths from COVID-19, a new weapon is being added to the vaccine arsenal. The U.S. Food and Drug Administration (FDA) is considering emergency use authorization (EUA) for Johnson & Johnson’s one-dose, non-mRNA shot. The new vaccine employs adenovirus vectors, a technology used in labs for decades that was FDA approved for the Ebola vaccine in December 2019. It’s the same technology used in the AstraZeneca and Sputnik V vaccines. To explain how adenovirus vectors work and what to expect from the new shots, Daniel Griffin, MD, PhD, the chief of the division of infectious diseases at ProHEALTHCare, joins us on this week’s episode. Listen and subscribe on Apple, Stitcher, Spotify, or Google so you don’t miss the next episode. And if you like what you hear, a five-star rating goes a long way in helping us Track the Vax! Serena Marshall: Before we get into adenovirus vectors and new vaccines that are coming out, let’s talk about adenoviruses. They cause a range of illnesses that people get every day, right? Daniel Griffin: That’s correct. I think people are unfortunately familiar with adenoviruses. These are the common cold viruses. All of us, at some point, at far too many points, have had the sniffles. You’ve had a cough. You felt crummy. If it’s a cold, it’s often adenovirus. Serena Marshall: Why would you use an adenovirus for a vaccine? Why does that make a good mechanism to deliver the vaccine, specifically when it comes to COVID? Daniel Griffin: There are a couple of reasons. I think the first is the common cold issue, and this is a mild virus. It’s not something that we worry about. It’s an inconvenience. Someday someone will cure the common cold, and that’ll be exciting. It also is one that we have a lot of experience making even more mild. So, we can actually use this common cold virus as a delivery system to allow our immune system to see spike proteins. To see basically something that our immune system can learn to respond to. It can hopefully allow us to develop an immune response so we don’t get sick with COVID. Serena Marshall: Talk about the history behind adenovirus vaccines. Daniel Griffin: We’ve been working with these really since the 1970s. This was the technology that was used when they had issues with Ebola in West Africa. Two Ebola vaccines were actually engineered using the viral vector technology, and were used in a couple hundred thousand people in the outbreaks in West Africa and the Democratic Republic of Congo. So in many ways this is technology that hundreds of thousands of people have used. We have a side-effect profile. We have safety-profile data. And now with AstraZeneca and Johnson and Johnson, we have a couple of COVID vaccines with really good data, as well as really impressive safety profiles. Serena Marshall: Viral vector vaccines have also gotten a little bit of a bad rap, specifically when it came to some research done with HIV. I know there’s concern that there’s an issue with preexisting immunity and adenoviral vectors. Can you explain why people should not be worried? Daniel Griffin: HIV is tricky. There are a couple of issues with HIV. One is that it’s constantly changing. It’s such a hard target because, as soon as you think you know what you’re going after, it’s already changed its genetic code. We’re starting to see a slower issue with COVID on those lines. The other is that when you activate cells, the cells that you activate are actually the ones that are most vulnerable to HIV. So when you try to use a vaccine and try to turn on the immune system, HIV takes advantage of that. We’re lucky in certain ways with COVID in that when you turn on the immune system early, when you give someone a vaccine, we’re seeing really great results. Some of the attempts to use this technology in HIV, unfortunately, as you bring up, they did not go well. Serena Marshall: Let’s talk about some of these vaccines that are using adenoviral vectors. How are they different from each other? Is it kind of like the mRNA, Pfizer and Moderna ones, where they’re relatively similar, just different research mechanisms in place? Daniel Griffin: With the Moderna and Pfizer vaccines, it’s the same RNA. It’s the same stuff inside the packaging; the packaging’s a little different. But with Sputnik, AstraZeneca and Johnson & Johnson, they’re using slightly different adenoviruses. So, there are a number of adenoviruses. Serena Marshall: We’ve seen the efficacy for these adenovirus vector vaccines to be a little bit different in some cases, a little bit lower than the mRNA ones. Why is that? Daniel Griffin: We don’t know. Most people, to be completely honest, were shocked at the efficacy that we saw with the mRNA vaccines. What I think is really critical is the ability of any of these vaccines to prevent you from dying of COVID. Once you get out to about six or seven weeks after you’ve started your vaccine regimen in a two-dose series or after you’ve gotten your Johnson & Johnson or your vector-based vaccine, you’re not going to die of COVID. I mean, your chance of dying of COVID is really pretty much erased. And that’s huge. There are little differences, whether or not you get the sniffles or a mild case. But what I think a lot of us really care about is, “Am I going to end up in the ICU? Am I going to end up on a ventilator, or am I going to die of COVID?” All the vaccines are tremendous at preventing that from happening.
