A group of US lawmakers has asked for the country’s drugs regulator to allow human challenge trials, a controversial strategy in which volunteers would be infected with the SARS-CoV-2 virus to check the efficacy of various vaccines.

Such trials could speed up the development of a vaccine, and the lawmakers have likened the current situation with COVID-19 to a war in order to seek the extraordinary approval. “Our situation in this pandemic is analogous to war, in which there is a long tradition of volunteers risking their health and lives on dangerous missions for which they understand the risks and are willing to do so in order to help save the lives of others,” a letter to Alex Azar, Secretary at the Department of Health and Human Services, and Stephen Hahn, Commissioner of the Food and Drug Administration, said. At more than 800,000 cases, the US has reported nearly one-third of all cases worldwide, as of April 23.

Usually, vaccines contain weakened, dead or altered forms of the virus or bacteria concerned, allowing the body to develop antigens to fight off a potential attack by the disease-causing virus or bacteria itself. In case of human challenge trials, the live virus would be injected--most likely into young, healthy volunteers--to see whether those who simultaneously get an under-trial vaccine get infected or not.

Injecting the live virus could potentially cause COVID-19 with all its implications. Such trials on humans have a long history, and most famously contributed to the development of drugs and vaccines for smallpox and polio.

Human challenge studies can help evaluate drugs that may be offered “either as preexposure prophylaxis [preventive] to prevent infection in individuals at high risk of infection”, or “as postexposure prophylaxis [treatment], given shortly after a potential exposure”--to prevent the onset of disease, noted a March 2020 study in The Journal of Infectious Diseases.

The letter also supports testing of various doses of vaccines simultaneously on different sets of volunteers--instead of starting with the lowest dose and increasing incrementally, as is the case with clinical trials usually--to save time. This could help identify and move a successful candidate vaccine from small safety trials to larger efficacy trials, the letter said.

Seventy-six vaccines are currently being trialled around the world, as per the WHO’s list, five at clinical evaluation stage and 71 at pre-clinical evaluation.

(Paliath is an analyst with IndiaSpend.)