I don't believe any of the vaccines use live virus.
Four COVID Vaccines Compared
This site has a helpful chart of the vaccines. The ones using an adenovirus vector are AstraZeneca and Johnson & Johnson.
Vaccine Q&A: Vaccines 101, mRNA and Adenoviruses
TA: If the mRNA vaccines are the first, what vaccines might be released next? I’ve also heard some talk about adenovirus vaccines. What are adenovirus vaccines? Are any of them being considered as COVID-19 vaccines?
Koci: Yes. Adenovirus-vectored vaccines are the other technology that has been close behind the mRNA-based vaccines in clinical testing. Of the six vaccines backed by Operation Warp Speed, the adenovirus vectored vaccines are the only other vaccines, besides mRNA vaccines, to make it to Phase III testing. That means, assuming things go well with this phase of testing, they will be the next ones that should get emergency use authorization – probably in January or February 2021.
Instead of hiding Greek soldiers, the adenovirus releases genes.
Like the mRNA vaccines, the main idea behind adenovirus vaccines is to get genetic material that encodes SARS-CoV-2 genes into your cells and get your cells to make the virus proteins. The difference is in how they do this. Where the mRNA vaccine is just the mRNA protected by a chemical shell, adenovirus vectored vaccines use a virus we know is harmless to act as a Trojan horse. But instead of hiding Greek soldiers, or anything dangerous, the adenovirus releases genes that encode the SARS-CoV-2 spike protein.
Adenoviruses are a family of viruses that have dozens, maybe hundreds, of members. Most don’t cause any known disease, or they only cause mild “common cold”-like symptoms. Scientists developed a way to use strains of adenoviruses that don’t cause disease as a delivery system for vaccines. So we’re using one virus to deliver the vaccine against another.
The genes for the protein that we want the immune system to respond to are inserted into the adenovirus genome as DNA. Then the person to be vaccinated against SARS-CoV-2 is infected with this harmless adenovirus. When the adenovirus gets into your cells the DNA is turned into mRNA, causing the cells to make the vaccine proteins, which triggers the immune response. I’ll also point out that when we insert these vaccine genes into the adenovirus, we also remove genes from the adenovirus so that it can’t replicate in the vaccinated person. This is done as an added safety precaution.
Like the mRNA vaccines, this type of vaccine has been around as an idea for a while, and there are several adenovirus-vectored vaccines in phase 1 and 2 clinical trials but none that I’m aware of that are FDA approved and currently being used in people.
Koci: The biggest advantage here is, even though there aren’t any adenovirus-vectored vaccines being used in people today that I’m aware of, scientists have been using this technology in the lab for decades. The process of inserting genes into the adenovirus vectors is routine for a lot of labs. It does involve more steps than mRNA vaccines, but those steps have been optimized so it can still be done pretty quickly. That makes these types of vaccines easy to make a lot of quickly and relatively cheaply. Also, once assembled, adenovirus-vectored vaccines are pretty stable, so they don’t have to be kept at really low temperatures.
One issue that has slowed down the development of these vaccines is all the other adenoviruses out in nature. Many don’t make us sick, and some are unknown to science. Vaccine producers have been trying to find the right adenovirus to use for the vaccine – one that your immune system hasn’t seen before. If the adenovirus carrying the vaccine looks too much like an adenovirus your immune system has seen before, your immune system will attack and destroy the vaccine before it has a chance to do its job. Companies have been working for years to fix this issue. Looking at the early data from the Oxford/AstraZeneca and Johnson and Johnson trials suggests they may have succeeded.
