RAPS is currently tracking the development of no fewer than 42 potential vaccines for COVID-19, but even that is barely half the number of vaccines that have already been announced. There’s no doubt that some of those announcements were little more than opportunities to gain a quick PR boost for companies, universities, and countries that have no real intention of investing the resources necessary to develop a vaccine against SARS-CoV-2. Even among those being tracked, 20 are still no further along than the “pre-clinical” stage and have not entered human trials. Still, there are 14 vaccines that are at least in Phase 2 or later, where they’re being tested for both safety and efficacy.
Some of these you’ve definitely heard about on the U. S. news—the Moderna vaccine which recently reported good results in a U. S. trial, the Oxford vaccine that’s already moving to phase 3 in multiple countries, and the Pfizer/BioNTech vaccine which isn’t far behind. Others have attracted little attention even though they’re already in phase 3 trials involving thousands of volunteers. But one prominent vaccine effort may already be out of the running … and almost also certain to rake in least $1 billion.
Not only are there a record number of vaccines in development to fight COVID-19, the array of medical technologies being deployed is breathtaking. Vaccines like the ones from Moderna and Pfizer employ not just one previously untested technology in human vaccines, but several.
There are four vaccines at this moment that have entered into Phase 3 testing. One of those is the widely discussed Oxford vaccine that’s heading into testing in three countries now, with more to come. Those trials could have early results as soon as September. Assuming it’s effective, it could be in the veins of healthcare workers in the U. K. well before the end of the year, and available to some in the U.S. around New Years.
Still, there are other vaccines even further along the deployment path. These include a pair of Chinese vaccines. One of these, the Sinopharm vaccine, uses a “dead” coronavirus. That’s an odd thing to say about something that’s not definitely alive in the first place, but these dead or “inactivated” vaccines are a traditional approach used on many diseases. In this case, the vaccine involves the use of the whole SARS-CoV-2 virus, damaged by heating so that it cannot reproduce. A non-peer reviewed release from China National Biotec Group declared that this vaccine produced a "strong neutralizing antibody response" in Phase 2 trials. It’s now entering Phase 3 trials in the United Arab Emirates, where they’re hoping to recruit up to 15,000 volunteers. However, since the early surge of cases in the UAE appears to have been largely brought under control, and the number of active cases in the nation is down to less than 6,500, it’s unclear how effective Abu Dhabi will be as a test site in determining efficacy.
But it’s another Chinese vaccine that’s more interesting … in an “almost certainly less effective” way.
On the same day that Oxford dominated the headlines with data from the latest trials of its vaccine, U. K. medical journal The Lancet published phase 2 trial results from CanSino Biologics. Like the Oxford virus, the CanSino virus takes components of the 2019 novel coronavirus and embeds them into the shell of an existing virus, in this case a weakened adenovirus called Ad5. Adenoviruses are extremely common and cause everything from colds to pink eye. The version of Ad5 used in the CanSino vaccine has been weakened by removing a pair of genes and has been a common platform for experiments involving a transfer of genes.
And … here’s the problem. While Phase 1/2 trial results on Moderna, Pfizer, and Oxford vaccines showed over 90% of people developing high levels of neutralizing antibodies to SARS-CoV-2 proteins, with CanSino that number was just 59%. Meaning that almost half the people might not be getting any real immunity from the vaccine. The overall level of antibody production also appears to be significantly lower than that seen with other leading vaccines.
Why the issue? Well, Adenovirus Ad5 is common. Also, those who have recently been infected by Ad5 develop immunity. Add those two factors together, and over half the volunteers in the trial already had some level of immunity to Ad5. Those volunteers had only a weak response to the vaccine, and didn’t reliably develop neutralizing antibodies to the COVID-1 components. Since Ad5 is so common, in some areas 75% or more of adults have been exposed. This would seem to indicate that CanSino is never going to provide the level of coverage that would be needed to provide herd immunity.
Still, expect this vaccine to be used, at minimum, millions of times. That’s in part because CanSino is being developed in conjunction with China’s Central Military Commission, which has already approved the vaccine for use in the armed forces. As Reuters reported in June, it’s unclear whether using the vaccine will be “mandatory or optional,” but expect it to be used. China has selected two different vaccine candidates for use by other parts of the government.
There’s another reason why Chinese vaccines like CanSino may get widespread use around the world even if they prove to be significantly less effective than other leading candidates. As CNN reported on Thursday, China announced a $1 billion loan to countries in Latin America and the Caribbean expressly for them to buy Chinese-made COVID-19 vaccines. With vaccines in high demand, and nations like the United States already laying out billions for access to the Oxford, Moderna, and Pfizer vaccines, the availability of these leading candidates may be months away for much of the world. So China is offering a bargain candidate to other countries—with low, low financing. A 50% effective vaccine doesn’t sound so bad, if it’s the only vaccine you can afford.
But what about the Oxford vaccine? If it also uses an adenovirus to carry the SARS-CoV-2 proteins, then isn’t it facing the same potential for running into existing immunity?
Well, rather than using a common human adenovirus, the Oxford team went outside the box. Outside the human box. The adenovirus they selected for their vaccine is one that actually circulates among chimpanzees. Which … yes, that does seem odd at first glance. The chimpanzee virus has also been modified to make it even less capable of reproducing in human cells. That combination means that the vaccine shouldn’t meet with the kind of existing immune response that’s interfering with the effectiveness of CanSino, but also won’t be giving anyone chimp eye. In the recently completed portion of the phase 2 trial, the Oxford vaccine generated neutralizing antibodies in 100% of volunteers.
There’s little doubt that the Oxford vaccine is going to be significantly more effective than the technically similar CanSino … for those nations which can afford it.
