Vaccines trials give hope but should be handled with caution

Xavier Symons
June 2, 2020
Reproduced with Permission

The development of a COVID-19 vaccine is a beacon of hope as the world emerges from the ravages of the coronavirus pandemic. Scientists believe that an effective vaccine could be identified before the end of the year, with ten major clinical trials currently taking place worldwide. Last week a phase one trial - a small human trial to determine safety and dosage toxicity for a drug - began in Melbourne and Brisbane, with about 130 participants receiving an initial dose of an American-manufactured vaccine. A similar trial will shortly begin at Flinders University in South Australia.

But human trials of COVID-19 vaccines raise a range of ethical questions, including whether it is permissible to fast track clinical trials to ensure a vaccine is quickly made available for public use. Skipping stages in a coronavirus trial may speed up vaccine development, yet it could jeopardise the reliability of results, and may increase the risk of harm to participants. Scientists are walking an ethical tightrope between rapidly gathering results and ensuring the reliability and safety of a new vaccine.

Some trials have already produced promising results. Data from a small initial trial of American pharmaceutical company Moderna's COVID-19 vaccine suggests that the vaccine can produce neutralizing antibodies to the coronavirus at levels greater than recovered COVID-19 patients. Some participants in the trial have fallen moderately ill after receiving the vaccine, yet the side-effects "have been transient and self-resolving", according to a Moderna spokesperson.

Moderna is already preparing for a much larger trial of the vaccine, in which scientists will test the drug on several thousand participants to determine whether it actually provides immunity to COVID-19. Yet large scale trials are often difficult to run - all the more so when governments are trying to decrease the rates of COVID-19 community transmission. Researchers will have to wait for people in the control arm of the study - those participants who have not been vaccinated - to be infected with the virus before they can determine if the vaccine is effective.

Experts like Stanley Plotkin, former head of vaccines at the US pharmaceutical giant Sanofi Pasteur, are concerned that it could take several months, even years, for participants to be exposed to the virus. This could delay the vaccine development process and leave governments without a definitive exit strategy from the COVID-19 pandemic.

To speed up results, some scientists have suggested running challenge trials. These intentionally expose young and healthy vaccinated participants to the coronavirus.

But others object. Is it really ethical to intentionally give a trial participant COVID-19 in the absence of an effective treatment? "At the moment, because we don't have a rescue therapy we have to approach challenge studies extremely cautiously," said Professor Andrew Pollard, an immunologist who is leading a trial of a COVID-19 vaccine developed by a team at the University of Oxford's Jenner Institute.

Moderna is hopeful that within a few months it will have trial data showing little to no infection among a statistically significant proportion of vaccinated study participants.

But most vaccines are not 100 percent effective. It could take several years, furthermore, for study investigators to gather sufficient data to prove the safety and efficacy of the vaccine for participants.

As Moderna Chief Medical Officer Tal Zaks recently said, it is likely that "we're going to have a pile of vaccines [before] having actual data that proves its safety profile and benefit". That is, governments will likely approve and mass produce a vaccine before they have gold-standard evidence demonstrating safety and effectiveness. The data will be good, but not certain.

A vaccine that protects most people is certainly better than no vaccine – provided it doesn't seriously harm some people. Health authorities need to think carefully about how they will deal with the risks involved in rolling out a potentially ineffective - or worse, dangerous - vaccine.

We can't risk doling out a vaccine that begins with fireworks and ends with funerals.