Yes there is a 3rd dose of Covid-19 vaccine. The Moderna COVID-19 Vaccine is is a series of two shots which is administered one month apart. An additional, or third, dose to be administered at least 28 days following the two-dose regimen of the same vaccine to individuals ages 12 or older for who have undergone solid organ transplantation, or who are diagnosed with conditions that are considered to have an equivalent level of immunocompromise.