- The UK government approved plans to conduct a coronavirus vaccine challenge trial that will involve 90 healthy volunteers aged 18 to 30.
- Volunteers will be quarantined in a hospital ward and inoculated with vaccine candidates before being intentionally exposed to the SARS-CoV-2 virus that causes COVD-19.
- The study’s goal is to speed up research and determine whether the vaccine candidates are effective at blocking the infection or preventing severe illness.
Discussions about vaccine challenge trials started several months ago when certain vaccine makers were already worrying that there might not be enough COVID-19 cases to allow the research to proceed faster. Without enough exposure to the virus, it’s impossible to tell how effective a vaccine candidate might be. Phase 1 trials started in the early months of the pandemic when the caseload was quite high. To determine the efficacy of a vaccine candidate, researchers will follow up on volunteers as they live their regular lives, where they risk random exposure to the virus. The fewer the cases in a community, the longer the researchers have to wait before they can draw conclusions. On the other hand, challenge trials allow drug makers to intentionally infect volunteers with the virus intentionally in a controlled environment and observe whether the vaccine can prevent infection or severe illness.
Challenge trials are a standard medical practice, but they usually involve medical conditions that have known treatments or cures. There’s no cure for COVID-19, and available therapies can’t save all patients. Still, the World Health Organization has already agreed to COVID-19 challenge trials, providing guidelines for interested parties. Separately, volunteers have signed up for such trials by the tens of thousands. Chatter about challenge trials died down a bit until recently, now that multiple vaccine candidates have reached Phase 3 trials. And now, the UK government has approved one such experiment.
90 healthy volunteers aged 18 to 30 will be quarantined in a north London hospital ward. They’ll be vaccinated with one or several of the vaccine candidates currently being tested in the country. Then they’ll be intentionally exposed to the SARS-CoV-2 virus and kept under observation.
The UK government announced the measure on Tuesday morning, but the challenge trial won’t start until some point in early 2021. By then, some of the COVID-19 vaccine frontrunners will have published their final results for Phase 3 trials, including AstraZeneca, Moderna, and Pfizer. Some will say that a challenge trial might not be needed considering that Pfizer estimates it will have results in about a month. Not to mention that the coronavirus is surging in the US and Europe, so there’s likely more than enough exposure for regular Phase 3 trials to proceed.
Others will also criticize the limited data the vaccine would yield. The challenge trial can only include a few dozen volunteers compared to Phase 3 trials, which need at least 30,000 volunteers in the US. And the fact that there are no other COVID-19 cures available forces researchers to limit participation to healthy young adults under 30. That means the results might not be relevant to other categories of people.
Still, there is no telling whether any of the frontrunners will prove to be safe and effective. With hundreds of coronavirus vaccine candidates in the works, challenge trials might offer an additional avenue for speeding up research.
“Human challenge studies can increase our understanding of COVID-19 in unique ways and accelerate development of the many potential new COVID-19 treatments and vaccines,” Dr. Chris Chiu told ABC News. Chiu represents the Department of Infectious Disease at Imperial College London, and he will be the lead researcher on the study.
The British government has partnered with hVIVO, the Imperial College University, and the Royal Free Hospital to run the trial.
hVIVO chief scientist Andrew Catchpole explained that a variety of precautions are taken to limit the risks for volunteers. The subjects will need to be healthy and they’ll be exposed to a version of the virus that will be engineered in a lab.
“So just like any other clinical trial, what you would expect is that any product we put into a human needs to undergo very tight regulations, and this is no exception to that,” Catchpole said. “So the virus, which we would inoculate them with, has been manufactured to the very high standards, a medical grade version of the virus that undergoes very high regulatory scrutiny to make sure that that virus is safe and suitable for use — just like you would expect for any other licensed medicine.”
The revelation that a company can manufacture a different version of COVID-19 might have an unwanted side effect and fuel conspiracy theories that claim the virus was man-made in China. Of note, the US has been developing a SARS-CoV-2 strain for potential challenge trials as well.
Scientists in the UK’s challenge trial will use a low dose of the virus to prevent severe symptoms, but the doctors will need to get the right balance. “We are looking to induce infection, but not necessarily looking to induce disease,” Catchpole said.
The volunteers will be infected by inhaling a diluted dose of the virus, and then they’ll be monitored closely inside the hospital. It’s unclear at this time whether the study will use a placebo control group. If so, those volunteers will be infected with the virus without having any potential protection, which is far more dangerous in a challenge trial. Placebo groups receive shots as well, but volunteers in vaccine studies have no idea whether they got the drug or not. The researchers observing them are usually unaware of which volunteers receive a placebo and which ones get the real drug.
Interestingly, an added benefit of the challenge trial is that it might explain exactly what sort of viral load is enough to infect people. This would help public health officials elaborate on additional safety measures for the general population. Even if vaccines are available this winter, it’ll be at least a year until they’re widely administered and the pandemic can be beaten, even in developed nations like the US. And people will still have to observe safety measures, including face masks, once vaccination campaigns begin.
The results of the UK challenge trial will be made available in just two months, according to Catchpole. By the time that happens, we might already COVID-19 vaccines that are approved by the FDA.
The hVIVO exec also stressed that challenge trials could provide results a lot quicker than traditional research. “What happens with the traditional studies is you vaccinate people, and they go about living their normal lives, and it’s just purely by random luck whether they’re actually exposed to the virus or not. Hence, it can take a very long time to establish efficacy in the field,” Catchpole continued. “And you’re totally dependent on how much virus is going on [around] the community. Challenge studies we’re able to conduct safely and all year round, irrespective of how much virus is going on [around] the community.”
