The findings emphasized the importance of contagious people covering their mouth and nose when sick to protect others, Dr. Chiu told CNN.
None of the study volunteers developed lung issues as part of their infection, CNN reported. Dr. Chiu said that’s likely because they were young, healthy and received tiny amounts of the virus. All of the participants will be followed for a year to monitor for potential long-term effects.
Throughout the study, the research team also conducted cognitive tests to check the participants’ short-term memory and reaction time. The researchers are still analyzing the data, but the results “will really be informative,” Dr. Chiu told CNN.
Now the research team will conduct another human challenge trial, which will include vaccinated people who will be infected with the Delta variant. The researchers intend to study participants’ immune responses, which could provide valuable insights about new variants and vaccines.
“While there are differences in transmissibility due to the emergence of variants, such as Delta and Omicron, fundamentally, this is the same disease and the same factors will be responsible for protecting it,” Dr. Chiu said in a statement.
The research team will also study the 18 participants who didn’t get sick in the first human challenge trial. They didn’t develop antibodies, Dr. Chiu told CNN, despite receiving the same dose of the virus as those who got sick.
Before the study, all of the participants were screened for antibodies to other viruses, such as the original SARS virus. That means the volunteers weren’t cross-protected, and other factors may play into why some people don’t contract COVID-19. Future studies could help researchers provide better advice about protection if new variants emerge or a future pandemic occurs.
“There are lots of other things that help protect us,” Dr. Chiu said. “There are barriers in the nose. There are different kinds of proteins and things which are very ancient, primordial, protective systems ... and we’re really interested in trying to understand what those are.”
A version of this article first appeared on WebMD.com.