Can people who are immunized against the coronavirus still pass it on to others? A new study will attempt to answer the question by tracking infections in vaccinated college students and their close contacts, researchers said Friday.

The results are likely to be of great interest as they can help determine how careful vaccinated people need to be – for example, whether they can throw away their masks or need to keep wearing them to protect unvaccinated people.

According to a New York Times database, more than 87 million have received at least one dose of a coronavirus vaccine. The Centers for Disease Control and Prevention has advised that fully vaccinated Americans can gather in small groups indoors without any precautions, including masks, but should still wear masks in public.

The reason is that it is not yet certain that vaccinated people will not be infected for a short time and that the virus will not be transmitted. Clinical trials with the vaccines should only assess whether the vaccines prevent serious illness and death. Manufacturers are now collecting information on whether the vaccines can also prevent infection and swabbing the volunteers’ noses every two weeks.

However, this method is inadequate because the tests are too infrequent to detect all infections and fail to track the spread of the virus to participants’ contacts, said Dr. Larry Corey, a vaccine development expert at the Fred Hutchinson Cancer Research Center in Seattle and a lead on the new study.

“The only way to do this is by sampling very frequently, and we cover our basics by doing this every day,” said Dr. Corey. “It will be the most thorough look at the problem.”

The new study will include more than 12,000 college students vaccinated with the Moderna vaccine at more than 20 universities in the United States. Half of the students will be randomly selected to receive the vaccine right after they enroll, while the other half will receive the vaccine four months later.

All participants dab their noses daily to look for the virus, provide regular blood samples to look for antibodies, and answer questions through an app. Scientists will follow the students for five months.

By closely monitoring students, scientists expect to be able to track infections in the first 24 or 48 hours and determine how long one infected person can pass the virus on to others, said Dr. Corey. Over time, the scientists expect that around 25,500 close contacts of the participants will be asked to wipe their nose daily for two weeks, provide two blood samples, and complete weekly questionnaires.

College students are an ideal population to study post-vaccination transmission. They are among the highest rates of coronavirus infection, in large part because they live in crowded dormitories and have more social contacts than older adults, while hospital stays and deaths are fortunately comparatively low. American colleges and universities have reported more than 530,000 cases since the pandemic began.