With thousands of people dying of Covid-19 every day, the sooner a vaccine can be considered safe and effective, the better. But fax development is a long process that is not easy to harden. In part, this is because of the final step in testing each vaccine: the Phase III trial.
Phase III studies require tens of thousands of volunteers, each receiving a placebo as an experimental vaccine. Then vaccine developers have to wait until a statistically significant number of them, which normally go about their lives, finally become naturally infected. This step alone can often take years.
When it comes to Phase III research for a Covid-19 vaccine specifically, there are additional concerns about the reality of fluctuating infection rates around the world, making it difficult to set up a successful trial where participants are likely to will naturally become infected.
Oxford University fax researchers have already had to change the location of their Phase III trial from the UK – where, in June, infection rates had fallen – to Brazil and South Africa, where rates began to rise. A team in China did something similar, changing the location of their Phase III trial from mainland China to the United Arab Emirates.
In light of these concerns, some epidemiologists and scientists are calling for what is being called a trial for human challenge. Instead of chasing the moving target of infection prey and waiting for participants to become naturally ill, a human challenge test involves a small group of young, healthy participants deliberately infected in a lab setting. The challenge study alone could last about a month, but it would have to happen after a trial to determine the exact dosage of a virus, and before a larger-scale safety study. But all this could be even faster than a typical Phase III trial.
This is not a new concept. Trials for human challenge have been used to develop vaccines or treatments for many diseases, such as cholera, typhoid, malaria, influenza, and common cold viruses. But what sets Covid-19 apart from these diseases is that it does not currently have effective treatment. Because it is so new, we are also not fully aware of its long term effects on health. Unlike other human challenge studies, a Covid-19 challenge test would involve a risk of serious illness – and even death.
It is because of these risks that a Covid-19 challenge test would be limited to young and healthy, who are at the lowest risk of harm. But there are questions about ethics. Would artificially infecting someone in a lab setting provide useful information on how to prevent natural infection?
“I would have to say that one of the problems with the challenge model … is that it’s an unnatural inoculation,” said Dr. Ronald Turner of the University of Virginia, who has been conducting challenge research for ordinary people since the 1980s. cold viruses. Turner says determining an accurate viral dose and route of infection to replicate a natural infection can pose scientific problems. “This raises problems about the ability to extrapolate your result in the natural setting. And so I think these technical issues, along with the ethical issues associated with a potentially deadly challenge, pose some real problems. ”
Other questions regarding studies on human challenge include whether data derived from a group of only young and healthy people would be valuable in developing a vaccine that works for everyone. But advocates for human challenge studies say a vaccine that protects the group would still help slow the spread of the virus.
‘If we could protect young, healthy people with a good vaccine, especially one that blocked transmission and infection, that would greatly help our ability to get back to normal, because they were out of the transmission loop and could work and able to go to school and other things, “said epidemiologist Marc Lipsitch, co-author of an article in March advocating preparation for possible studies for human challenge.
Another question is whether we really need to apply to this ethically dubious form of clinical trial, given that a handful of vaccines are already in Phase III studies. It is possible that these phase III trials are rapid and successful, especially given high rates of infection at clinical trial sites, such as in the US, South Africa, and Brazil.
Even though no Covid-19 human challenge tests are currently planned, more than 30,000 people from nearly 150 countries have already said they would volunteer for one if the opportunity presented itself, via the grassroots movement 1DaySooner.
The question is, should we leave them?
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