Human vaccine trials against COVID-19: How far is too far?

In the search for a vaccine against Covid-19, some of the world’s most respected vaccine researchers and medical ethicists, and even the World Health Organization, have started discussions about deliberately infecting human volunteers with the virus in order to assess the effectiveness of potential vaccines. William Haseltine has not only called this proposal “unnecessary, uninformative, and unethical” but also warns that it risks destroying trust in the integrity of science and medicine for generations to come.

The rationale for considering “human challenge trials” is that infection rates are relatively low. If estimates suggesting that 7% of the UK population is currently infected are correct, this poses problems for testing vaccines, given that volunteers need to be sufficiently exposed to the virus in order to test the efficacy of a vaccine. The efficacy cannot be demonstrated if the chances of being in contact with an infected person are too low. Several scientists have stated in The Guardian that a volunteer programme should be considered “very seriously”, but under very strict conditions: only young, healthy people should be used and – considering that Covid-19 can also have serious side-effects for this group – a very effective therapy should be developed in the few cases where something goes seriously wrong.

A recent WHO white paper also advocates going ahead with vaccination trials. Calling Covid-19 an extraordinary threat to global public health and other aspects of public life, human challenge trials might “not only accelerate Covid-19 vaccine development, but also make it more likely that the vaccines ultimately deployed are more effective”.

Haseltine is sceptical of the proposal. While long-term immunity against illnesses as smallpox, polio, typhoid, diphtheria and typhus has been accomplished, there are just as many diseases for which no truly effective vaccine exists, including HIV/AIDS, malaria, and tuberculosis. And some vaccines have also been proven to do more harm than good. Haseltine feels vaccination is unnecessary because authorities around the world have executed proven public-health measures such as strong stay-at-home orders, vigorous disease detection and contact tracing. He also calls the proposal uninformative, as previous studies have shown that successful vaccination of young, healthy adults can still mean that the vaccine fails in older populations. Perhaps most importantly, human challenge trials are unethical considering that Covid-19 causes multi-system disease in about 20% of those infected and a number of volunteers will be permanently harmed.

The general public remains understandably suspicious about the vaccination industry and its lobbying power, especially with the recent news that a highly reputable journal such as The Lancet has pulled a study analysing the effects of hydroxychloroquine in combatting Covid-19 after the authors expressed concerns about the quality and veracity of their data. While the study supposedly proved the harmfulness of the well-known Zelenko protocol, other studies that had been paused in the wake of the Lancet study have now been resumed and may identify the protocol as a serious alternative for vaccination.

Edited by: Dr. Olivier Vonk