***TASK*** the task is to summarize an input biomedical literature in six sentences 
    ***INPUT*** the input is a biomedical literature 
    ***OUTPUT*** the output is the summary of an input biomedical literature in six sentences 
    ***DOCUMENTATION*** 
    ***EXAMPLES*** 
    Input: Prophylaxis reduces cytomegalovirus ( CMV ) disease , but is associated with increased costs and risks for side effects , viral resistance and late onset CMV disease . Preemptive therapy avoids drug costs but requires frequent monitoring and may not prevent complications of asymptomatic CMV replication . Kidney transplant recipients at risk for CMV ( D+/R− , D+/R+ , D−/R+ ) were r and omized to  prophylaxis ( valganciclovir 900 mg q.d . for 100 days , n = 49 ) or preemptive therapy ( 900 mg b.i.d . for 21 days , n = 49 ) for CMV DNAemia ( CMV DNA level > 2000 copies/mL in ≥ 1 whole blood specimens by quantitative PCR ) assessed weekly for 16 weeks and at 5 , 6 , 9 and 12 months . More patients in the preemptive group , 29 ( 59 % ) than in the prophylaxis group , 14 ( 29 % ) developed CMV DNAemia , p = 0.004 . Late onset of CMV DNAemia ( > 100 days after transplant ) occurred in 11 ( 24 % ) r and omized to prophylaxis , and none r and omized to preemptive therapy . Symptomatic infection occurred in five patients , four ( 3 D+/R− and 1 D+/R+ ) in the prophylactic group and one ( D+/R− ) in the preemptive group . Peak CMV levels were highest in the D+/R− patients . Both strategies were effective in preventing symptomatic CMV . Overall costs were similar and insensitive to wide fluctuations in costs of either monitoring or drug Both preemptive therapy and universal prophylaxis are used to prevent cytomegalovirus ( CMV ) disease after transplantation . R and omized trials comparing both strategies are sparse . Renal transplant recipients at risk for CMV ( D+/R− , D+/R+ , D−/R+ ) were r and omized to 3‐month prophylaxis with valacyclovir ( 2 g q.i.d . , n = 34 ) or preemptive therapy with valganciclovir ( 900 mg b.i.d . for a minimum of 14 days , n = 36 ) for significant CMV DNAemia ( ≥2000 copies/mL by quantitative PCR in whole blood ) assessed weekly for 16 weeks and at 5 , 6 , 9 and 12 months . The 12‐month incidence of CMV DNAemia was higher in the preemptive group ( 92 % vs. 59 % , p < 0.001 ) while the incidence of CMV disease was not different ( 6 % vs. 9 % , p = 0.567 ) . The onset of CMV DNAemia was delayed in the valacyclovir group ( 37 ± 22 vs. 187 ± 110 days , p < 0.001 ) . Significantly higher rate of biopsy‐proven acute rejection during 12 months was observed in the preemptive group ( 36 % vs. 15 % , p = 0.034 ) . The average CMV‐associated costs per patient were $ 5525 and $ 2629 in preemptive therapy and valacyclovir , respectively ( p < 0.001 ) . However , assuming the cost of $ 60 per PCR test , there was no difference in overall costs . In conclusion , preemptive valganciclovir therapy and valacyclovir prophylaxis are equally effective in the prevention of CMV disease after renal transplantation Oral ganciclovir prophylaxis and intravenous preemptive therapy are competitive approaches to prevent cytomegalovirus ( CMV ) disease after renal transplantation . This trial compared efficacy , safety and long-term graft outcome in 148 renal graft recipients r and omized to ganciclovir prophylaxis ( N = 74 ) or preemptive therapy ( N = 74 ) . Hierarchical testing revealed ( i ) patients with CMV infection had more severe periods of impaired graft function ( creatinine clearance(max-min ) 25.0 + /- 14.2 mL/min vs. 18.1 + /- 12.5 mL/min for patients without CMV infection ; p = 0.02),(ii ) prophylaxis reduced CMV infection by 65 % ( 13 vs. 33 patients ; p < 0.0001 ) but ( iii ) creatinine clearance at 12 months was comparable for both regimes ( 54.0 + /- 24.9 vs. 53.1 + /- 23.7 mL/min ; p = 0.92 ) . No major safety issues were observed , and patient survival at 12 months was similar in both groups ( 5 deaths [ 6.8 % ] vs. 4 [ 5.4 % ] , p = 1.0000 ) . Prophylaxis significantly increased long-term graft survival 4 years posttransplant ( 92.2 % vs. 78.3 % ; p = 0.0425 ) with a number needed to treat of 7.19 . Patients with donor + /recipient + CMV serostatus had the lowest rate of graft loss following prophylaxis ( 0.0 % vs. 26.8 % ; p = 0.0035 ) . In conclusion , it appears that routine oral prophylaxis may improve long-term graft survival for most renal transplant patients . Preemptive therapy can be considered in low risk patients in combination with adequate CMV monitoring BACKGROUND The impact of cytomegalovirus ( CMV ) infection and disease on long-term outcome  after kidney transplantation is still unsettled . METHODS Between 1994 and 1997 , 397 consecutive first kidney graft recipients and 74 retransplants were included in the study and followed prospect ively until December 31 , 2001 . CMV infection ( CMV pp65 antigenemia ) and CMV disease were recorded once weekly during the first 100 days after transplantation . No CMV prophylaxis or preemptive therapy was given . In a multiple Cox proportional hazard model allowing time-dependent covariates , the effects of asymptomatic CMV infection and CMV disease , recipient age and gender , retransplantation , living donor , panel-reactive cytotoxid antibodies , acute rejection , and graft loss were tested on overall mortality beyond 100 days post-transplantation . In a similar analysis , the effect of asymptomatic CMV infection and CMV disease plus other factors were tested on death censored graft loss beyond 100 days . RESULTS Median ( range ) follow up time was 66.6 ( < 1 - 86.9 ) months . The incidence of CMV infection and disease during the first 100 days was 62.8 % and 23.4 % , respectively . The number of total deaths was 96 ( 20 % ) , 82 occurred after the first 100 days . Independent risk factors for overall mortality beyond 100 days were asymptomatic CMV infection , RR = 2.90 ( 95 % CI 1.61 - 5.22 ) ( P= 0.001 ) , CMV disease , RR = 2.50 ( 95 % CI 1.31 - 4.79 ) ( P= 0.006 ) , both compared to no infection or disease , recipient age , RR = 1.066 per year ( 95 % CI 1.048 - 1.084 ) ( P < 0.001 ) , and graft loss in the whole study period RR = 7.88 ( 95 % CI 4.75 - 13.08 ) ( P < 0.001 ) . Asymptomatic CMV infection and CMV disease were not independent risk factors for death censored graft loss , but they significantly reduced graft survival uncensored for death , ( log rank P= 0.001 , respectively ) . CONCLUSION Asymptomatic CMV infection and overt CMV disease during the first 100 days increase the risk of recipient mortality beyond 100 days . This raises the question whether CMV prophylaxis should be given routinely after kidney transplantation 
    Output:
    
The results of the meta- analysis were as follows : the prophylactic protocol was significantly more effective than the preemptive protocol in reducing CMV infections and the recurrence rates of CMV infection ; both the preemptive protocol and the prophylactic protocol reduced the risk of CMV disease , with no significant differences ; no significant differences were observed in the risks of mortality , acute rejection , graft loss , other infections , or neutropenia between preemptive therapy and prophylaxis .
Preemptive protocol s are as effective as prophylaxis in reducing the risk of CMV disease in renal transplant recipients , whereas the prophylactic protocol s could more effectively reduce the CMV recurrence rates .