On Monday, the BioCubaFarma laboratory tweeted that Abdala—one of the two already in use— "shows an efficacy of 92.28 percent in its three-dose scheme".
The World Health Organization has set a 50-percent efficacy threshold for coronavirus vaccines to offer protection against the virus or disease.
The announcement came two days after authorities announced that Soberana 2, the other three-dose shot being developed in Cuba, was 62 percent effective after the first two shots.
Cuban President Miguel Diaz-Canel welcomed the news as an achievement which "will multiply pride" in the communist island nation.
Cuba has been relatively unscathed by the outbreak but has seen a recent sharp increase in cases, registering one of its worst days Monday with 1,561 confirmed infections in 24 hours. To date, it has recorded just over 169,000 cases and 1,170 deaths.
Under American sanctions, Cuba has a long tradition of making its own vaccines, dating back to the 1980s.
Nearly 80 percent of its vaccines are produced locally and it hopes to come up with the first locally-produced coronavirus shot in Latin America.
Cuba’s authorities have already started administering the experimental vaccines en masse as part of “intervention studies” they hope will slow the spread of the virus.
About a million of the country’s 11.2 million residents have been fully vaccinated to date.
Daily cases have halved in the capital, Havana, since the start of the vaccination campaign a month ago, using Abdala, according to official data.