The CDC recommends the mRNA vaccines Moderna or Pfizer-BioNTech because of their effectiveness and lack of concerning side effects. Unfortunately, people with a transplant and those who take immunosuppressive therapy are unlikely to develop a strong antibody response after vaccination. According to one study, only 17% of transplant recipients developed a detectable antibody response after one dose of the vaccine, and 54% of transplant recipients developed a detectable response after two doses of vaccine. Therefore, it's recommended that transplant recipients, especially those taking immunosuppressive therapy, should receive a third vaccine dose. They should also receive an updated booster dose at least two months after the primary series or last booster. After completing a two-shot series, the third dose of mRNA vaccine should be given at least four weeks after the second dose to SOT recipients taking immunosuppressive medications and to HSCT recipients who are within two years of transplantation or are taking immunosuppressive medication. The third dose of vaccine helps boost immunity. A different follow-up study showed that antibody levels were detectable in 68% of transplant patients four weeks after the third dose of vaccine. Vaccination should be completed at least two weeks before SOT or started one month after the transplant. The COVID-19 vaccines can be offered as early as three months after an HSCT.