When the UK’s Covid Vaccine Challenge was initially announced — a study set to deliberately infect healthy people with SARS-CoV-2 — I and many of my colleagues in science and public health condemned the approach. Human challenge trials can be useful, but they come at a risk to healthy volunteers. Only when we are absolutely certain that the benefits outweigh the risks should we proceed. This week, the UK government confirmed the trial would go forward as planned, but we are nowhere near the threshold that would warrant such a dangerous endeavor.
The risk to the 90 healthy volunteers who will be recruited for this trial is very real. The press release announcing the challenge claims that “the safety of volunteers is paramount” and highlights how only healthy young adults will be chosen. Yet it ignores the mounting evidence that even a mild case of Covid in a healthy young adult can lead to long term lung damage and other potentially serious lifelong symptoms. To make it worthwhile to put 90 healthy young people at risk for lifelong illness, the benefits have to be very real. But the reality is that this trial is likely to prove relatively meaningless.
Since the issue of human challenge trials for Covid-19 was first introduced last year, our understanding of the virus has evolved dramatically. We now know that the virus can change, and it can change quickly. One of the primary purposes of this vaccine challenge, at least according to the release, is to establish “the smallest amount of virus needed to cause infection, which will give doctors greater understanding of Covid-19 and help support the pandemic response by aiding vaccine and treatment development.” Yet given what we know of SARS-CoV-2 today, it is highly likely that the virus used in the challenge expected to begin in just a few weeks will be markedly different than the virus that the world will be dealing with when the results are released.
Take the UK variant of the virus, otherwise known as B.1.1.7. That virus is known to be up to 75% more transmissible than any previously known strain. We know, from another study in a lab setting, that SARS-CoV-2 can mutate beyond that level of transmissibility to become up to 600 times more transmissible than any of the variants seen to date. So whatever data we discover from this trial may become moot within days, weeks, or months, when the world is faced with a newer, more transmissible variant, able to infect with far fewer particles.
Beyond that basic fact, there is no need to actively infect healthy individuals when we are going to have real comparison data to work with from the millions of people already vaccinated and the hundreds of millions more who will be vaccinated in the near future. What could possibly be the reason behind actively infecting healthy people while the same data could be garnered through other, less risky means?
I can’t help but wonder if the answer doesn’t have more to do with profit rather than public health. A vaccine challenge would allow the UK to test its own national vaccine champion, the Oxford vaccine, against the virus, perhaps putting it an advantage at the risk of human lives. I sincerely hope this is not the case. But I have yet to read or hear another rationale that makes more sense. Yes, we need to develop new and second generation vaccines. Yes, we need the data to support their development. But risking the lives of ninety healthy volunteers isn’t the way to do it, when we have so many other options at hand.