字幕表 動画を再生する 英語字幕をプリント - [Daniela] In response to the coronavirus crisis, researchers are working at a breakneck pace to develop solutions that will allow economies to reopen safely and permanently. - Without an effective vaccine, we won't be able to get this pandemic under control and stop the devastation that it's currently causing all around the globe. - Vaccines can take an average of 10 years to develop, according to a 2013 study, but researchers and pharmaceutical companies are hoping to bring their vaccine candidates for the new coronavirus to market in 12 to 18 months. Some are even talking about getting Emergency Use Authorizations before the end of the year. So what is making it possible to expedite this process so dramatically? There are several factors, including prior knowledge of coronaviruses, specifically SARS and MERS, improvements in sequencing of viral genomes, advancements in bioengineering technologies, unprecedented government support and funding, plus a shortened testing timeline. Traditionally, after scientists develop a vaccine candidate, they run it through a series of tests. This starts in cells, and then transitions to animals, usually beginning with mice and eventually progressing to monkeys. Testing only advances from one phase to the next if it's proven to be safe and effective. - At that stage, you would then likely perform what we call a challenge study, so that would be vaccinating an animal then intentionally giving them the virus and seeing the impact of your vaccine on that disease model where, of course, you would hope to protect it. - Then they'd use that data to get approval from regulators like the FDA to begin human testing. There are three stages of human trials, each one testing more people than the last. Approval is required for each stage. Instead of this relay approach where researchers wrap up each set of experiments before embarking on the next round, developers are now doing many tests in parallel. - So we're not skipping steps, but we're doing things at the same time, which of course costs a lot more and is a lot more work than doing it one after the other, and that's the key difference. - The novel coronavirus was discovered and sequenced less than six months ago. Several candidates are already in phase one of human trials, including those made by Inovio and Pfizer, even as companies await results from animal studies. Moderna recently started phase two. Others are gearing up for phase two before phase one wraps up. - Our phase one trial will run for a year, but we're not going to wait for that full year period to have elapsed before we hopefully move on to the next stage of efficacy testing. - Because of the worry of COVID-19 being so devastating, we are expediting those processes, and this oughta concern, because we don't really know all that much about immunity to this virus, that we may be going too quickly, but so that's the balance here. - [Daniela] Vaccines work on a simple premise. They trick the body into thinking a virus has infiltrated it so the immune system kicks into action and starts producing antibodies and other defenses against parts of the virus. In this case, scientists think their target is the spike protein, which the coronavirus uses to get into cells. - It's been shown from SARS and MERS that the spike protein is the major protein on the outside of the virus of these coronaviruses to which erase neutralizing antibodies, and neutralizing antibodies is what you need to fight the infection. - So what would really end the pandemic is when there's enough immunity in the population, and either than immunity comes from everybody getting infected or it comes from a vaccine, and it's a much gentler path for everybody to get a vaccine than for everybody to get infected. - [Daniela] This concept is known as herd immunity. Dozens of companies and labs are trying various technologies to develop vaccines that would get us there quickly. Scientists say it's the largest, most collaborative vaccine development effort they've seen in their lifetimes. They're testing four main strategies, weakened viruses, proteins, viral vectors, and genetic code vaccines. Weakened or inactivated virus vaccines are the most common. That's your annual flu shot. We have the most experience with these, but they can also be costly and time-consuming to mass-produce, so in this case, they haven't been the preferred approach. Protein-based vaccines carry key parts of the virus into the body. For coronavirus, that's the spike protein. Sanofi and GlaxoSmithKline are among dozens of developers taking this approach. For viral vector vaccines, scientists use an inactivated virus and stuff it with the genetic code for the spike protein, which our cells then use to turn out viral proteins. The immune system then recognizes those as foreign. Johnson & Johnson is developing this type of vaccine for the coronavirus. - [Gert] We use adenovirus vector, and this adenovirus is a common cold virus which normally doesn't cause any major disease, just a common cold. In the adenovirus, it becomes replication incompetent. - [Daniela] In the fourth and final category are genetic code vaccines. These contain the instructions for the spike protein. COVID vaccines being developed by Inovio, Pfizer, and Moderna fall into this category. These types of vaccines have never been approved for humans before, but they're generating a lot of excitement. - The reason we're seeing them out in front is the speed. - The speed in the manufacturing and the development? - Yeah, really, both. Proteins are more diverse. They have all kinds of different shapes and characteristics and so you have to play with a lot more to actually get a protein-based vaccine made. - [Daniela] Pfizer is running multiple candidates through phase one trials in the U.S. and Germany to cut down on development time. - And even before we know whether the vaccine works or not, we're starting to ramp up manufacturing capacity so that we're ready to make it right away. The key things you have to establish to develop a vaccine are that it is safe, that it's effective, and that every time you make it, it comes out the same, so those key steps don't change whether you're going fast or you're going slow. - Changes in manufacturing can introduce unforeseen issues that could make a vaccine dangerous. That's what happened with the since-discontinued polio vaccine decades ago. Safety is a major concern, because vaccines are given to healthy people, so scientists have to ensure they don't affect things like liver or heart function among other factors. There are other issues as well. Even if companies are able to come up with a vaccine in less than two years, the vaccine research community is concerned with how they'd be able to produce and distribute it to everybody on the planet. - So we are aiming to produce one billion dose by the end of 2021, and some other companies are committing to the same kind of scale, either hundreds of millions or billions, but still, it will not be enough for everyone. - What is a big unknown is what the durability of that protection is. Is it going to be a year, two years, or even maybe, unfortunately, six months or less, because if it is measured in several months instead of years, which is entirely conceivable that that would be the case, then we have a secondary problem. How often do you need to boost somebody to keep that level of immunity up? - [Daniela] The final and perhaps most important hurdle for coronavirus vaccine development will be human behavior. - Are people gonna be accepting of this vaccine? That's been such a huge problem in this country. You know, if you have 50% of people saying I'm not gonna take it under any condition, then, of course, you've lost the whole battle.