Over the past 25 years, several randomized controlled trials have investigated the efficacy of different antiviral agents for cytomegalovirus (CMV) prophylaxis in allogeneic hematopoietic cell transplantation. We performed a systematic literature review, conventional meta-analysis, and network meta-analysis using a random-effects model and risk ratios (RRs) with corresponding 95% confidence intervals (CIs) as effect estimates. Fifteen randomized controlled trials were identified, including 7 different antiviral agents: acyclovir, ganciclovir, maribavir, brincidofovir, letermovir, valacyclovir, and vaccine. Twelve trials used placebo as comparator while 3 trials compared different antiviral agents. We found evidence for CMV disease and infection being significantly reduced by antiviral prophylaxis, with an RR of .66 (95% CI, .48 to .90) and .63 (95% CI, .50 to .79). Across the network, ganciclovir showed the best relative efficacy for CMV disease while letermovir provided first rank of being the best option for CMV infection. The risk for death was not significantly influenced by antiviral prophylaxis in the meta-analysis, with an RR of .92 (95% CI, .78 to 1.08), as well as in the network meta-analysis. In terms of safety, letermovir was at least similar in comparison with placebo and most agents while both letermovir and acyclovir showed significantly reduced risk for serious adverse events compared with ganciclovir, with RRs of .55 (95% CI, .30 to 1.00) for letermovir and .63 (95% CI, .42 to .93) for acyclovir. With a probability of 81%, letermovir appears to be the best option in terms of safety. Future randomized head-to-head comparisons are needed to evaluate the definite efficacy and safety of different prophylactic strategies.
