State daily Granma said the trials are being carried out on 28 patients who take one pill each day to test its capacity to reduce the chances of infection by some 90 percent in people exposed to the virus.

The trials are being done in Cardenas, a city in western Matanzas province with an accelerated population growth. There are currently 234 cases of HIV infection in the town, where about 30 new cases are reported annually.

The pill is delivered free of charge to the patients, considered "people at high risk of getting the disease," public health official Niura Perez told the daily.

As of October 2017, Cuba reported 23,283 cases of HIV infection nationwide, with 86 percent of the patients receiving free medical treatment.