***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 
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    ***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 Late‐onset cytomegalovirus ( CMV ) disease is a significant problem with a st and ard 3‐month prophylaxis regimen . This multicentre , double‐blind , r and omized controlled trial compared the efficacy and safety of 200 days ’ versus 100 days ’ valganciclovir prophylaxis ( 900 mg once daily ) in 326 high‐risk ( D+/R– ) kidney allograft recipients . Significantly fewer patients in the 200‐day group versus the 100‐day group developed confirmed CMV disease up to month 12 posttransplant ( 16.1 % vs. 36.8 % ; p < 0.0001 ) . Confirmed CMV viremia was also significantly lower in the 200‐day group ( 37.4 % vs. 50.9 % ; p = 0.015 at month 12 ) . There was no significant difference in the rate of biopsy‐proven acute rejection between the groups ( 11 % vs. 17 % , respectively , p = 0.114 ) . Adverse events occurred at similar rates between the groups and the majority were rated mild‐to‐moderate in intensity and not related to study medication . In conclusion , this study demonstrates that extending valganciclovir prophylaxis ( 900 mg once daily ) to 200 days significantly reduces the incidence of CMV disease and viremia through to 12 months compared with 100 days ’ prophylaxis , without significant additional safety concerns associated with longer treatment . The number needed to treat to avoid one additional patient with CMV disease up to 12 months posttransplant is approximately 5 Background . Cytomegalovirus ( CMV ) prevention can be achieved by prophylaxis or preemptive therapy . We performed a prospect i ve r and omized trial to determine whether renal transplant recipients with a positive CMV serostatus ( R+ ) had a higher rate of CMV infection and disease after transplantation when treated preemptively for CMV infection , compared with primary valganciclovir prophylaxis . Methods . Prophylaxis was 2 × 450 mg oral valganciclovir/day for 100 days ; preemptive patients were monitored by CMV-polymerase chain reaction ( PCR ) , and after a positive PCR test received 2 × 900 mg valganciclovir/day for at least 14 days followed by secondary prophylaxis . Valganciclovir dosage was adjusted according to renal function . Patients are followed up for 5 years and initial 12-month data are presented . Two hundred and ninety-six recipients were analyzed ( 168 donor/recipient seropositive [ D+/R+ ] , 128 donor seronegative/recipient seropositive [ D−/R+ ] ; 146 receiving prophylaxis and 150 preemptive therapy ) . Results . Overall , CMV infection ( asymptomatic CMV viral load ≥400 CMV DNA copies/mL proven by CMV-PCR ) was significantly higher in recipients under preemptive therapy ( 38.7 % vs. 11.0 % , P<0.0001 ) , with the highest incidence in D+/R+ preemptive patients ( 53.8 % vs. 15.6 % , P<0.0001 ) . D+/R+ recipients with preemptive therapy also had the highest rate of CMV disease ( CMV syndrome and tissue-invasive disease that was clinical ly diagnosed and biopsy proven ) ( 19.2 % vs. 4.4 % , P=0.003 ) . Renal function assessed by creatinine clearance was similar for both groups . Graft loss occurred in 7 vs. 4 patients on preemptive versus prophylactic therapy ( P>0.05 ) . Tolerability was similar for both treatment groups . Conclusions . Oral valganciclovir prophylaxis significantly reduces CMV infection and disease , particularly for D+/R+ patients . Hence , our study supports routine prophylaxis for all D+/R+ recipients BACKGROUND Cytomegalovirus ( CMV ) disease is a major complication of organ transplantation . We hypothesized that prophylactic treatment with valacyclovir would reduce the risk of CMV disease . METHODS A total of 208 CMV-negative recipients of a kidney from a seropositive donor and 408 CMV-positive recipients were r and omly assigned to receive either 2 g of valacyclovir or placebo orally four times daily for 90 days after transplantation , with the dose adjusted according to renal function . The primary end point was laboratory-confirmed CMV disease in the first six months after transplantation . RESULTS Treatment with valacyclovir reduced the incidence or delayed the onset of CMV disease in both the seronegative patients ( P<0.001 ) and the seropositive patients ( P=0.03 ) . Among the seronegative patients , the incidence of CMV disease 90 days after transplantation was 45 percent among placebo recipients and 3 percent among valacyclovir recipients . Among the seropositive patients , the respective values were 6 percent and 0 percent . At six months , the incidence of CMV disease was 45 percent among seronegative recipients of placebo and 16 percent among seronegative recipients of valacyclovir ; it was 6 percent among seropositive placebo recipients and 1 percent among seropositive valacyclovir recipients . At six months , the rate of biopsy-confirmed acute graft rejection in the seronegative group was 52 percent among placebo recipients and 26 percent among valacyclovir recipients ( P=0.001 ) . Treatment with valacyclovir also decreased the rates of CMV viremia and viruria , herpes simplex virus disease , and the use of inpatient medical re sources . Hallucinations and confusion were more common with valacyclovir treatment , but these events were not severe or treatment-limiting . The rates of other adverse events were similar among the groups . CONCLUSIONS Prophylactic treatment with valacyclovir is a safe and effective way to prevent CMV disease after renal transplantation The objective of this study was to define the incidence and significance of  acute rejection occurring in the first year following transplantation . The influence of contemporary induction immunosuppression on rejection , as well as the effect of rejection on graft and patient loss , renal function , and maintenance immunosuppression during the first year in 110 recipients of first cadaver renal transplants were analyzed . All patients received CsA , Aza , and prednisone for 30 days with withdrawal of Aza at 30 days and then prednisone at 105 days ; 57 patients were  prospect ively r and omized to receive ALG ( Merieux ) until serum creatinine was less than 300 mumol/L. Short-term ALG administration did not influence the incidence , severity , nature , or outcome of rejection episodes . Fifty-five ( 50 % ) patients had at least 1 rejection in the first 90 days . All patients with delayed graft function  and 7/8 ( 88 % ) sensitized patients ( current PRA greater than 50 % ) had at least 1 rejection episode ; 71 % ( n = 35 ) of all rejection episodes occurred in the first 30 days posttransplant . Patients rejection free at 90 days remained rejection free the entire first year . Graft loss was 18 % for rejections in the first month , 13 % for rejections occurring later ( P = NS ) ; 20 % ( n = 11 ) of patients had a second rejection and 1 % ( n = 2 ) had a third rejection . The risk of graft loss was 9 % with a first rejection , 38 % with a second rejection , and 50 % with a third rejection . Of 12 ( 22 % ) rejections that were steroid resistant , 10 ( 83 % ) were reversed with OKT3 . One-year graft survival for patients without rejection , with steroid-sensitive rejection , and with steroid-resistant rejection was 96 % , 88 % ( P = ns ) , and 58 % ( P less than 0.001 ) , respectively ; 1 year SCr was 168 + /- 93 , 196 + /- 77 ( P = ns ) , and 268 + /- 96 microMol/L ( P less than 0.05 ) , respectively . Patients free of rejection and with stable renal function continued to do well on maintenance CsA monotherapy , and they were more likely to be on CsA monotherapy than those with rejection episodes ( P less than 0.01 ) The study aim ed at analyzing the role of CMV infection as a risk factor for  rejection occurring after CMV infection because of the clinical consequences of the prevention of CMV infection that might lead to the decrease in rejection episodes .  Two hundred forty-two consecutive renal transplant patients were prospect ively checked for the occurrence of CMV infection . CMV infection was defined virologically by a positive viremia or/ and a positive viruria or/ and a seroconversion or/ and a significant rise of the anti-CMV antibody titers . Viremia , viruria , and serology were performed weekly for the first month and then at day 90 , day 180 , and every 6 months , and moreover if clinical symptoms related to a viral infection occurred . Rejection episode was defined by a creatininemia rise of 25 % , after cyclosporine nephrotoxicity and urological complications had been discarded , and by the response to the antirejection therapy , steroids , or OKT3 in case of steroid-resistant rejection . The outcome factor was rejection episode occurring from day 4 after the diagnosis of CMV infection . A patient undergoing " a rejection episode after CMV infection " could also be exposed to other potential confounding factors that can be considered as risk factors of rejection among our patients . Rejection occurring before CMV infection was the main factor because it was linked both to CMV infection itself and to " rejection after . " Thus infected and noninfected patients were r and omly paired off . To the noninfected patient of the pair was attributed the date of a fictitious CMV infection that was the date of the CMV infection of the infected member of the pair . Therefore , " rejection after " and " rejection before " were defined in infected and noninfected patients of the pair according to the time of onset of CMV infection of the infected member of the pair . The incidence of CMV infection was 65 % , 157 of the 242 patients were infected , and 85 not infected . Thus 85 pairs of infected-noninfected patients were studied . The incidence of " rejection after " the diagnosis of CMV infection was significantly higher in the group of patients with CMV infection : 45 % among infected ( 38/85 ) versus 10.60 % among noninfected ( 9/85 ) ( P < 0.0001 ) . Among the 85 pairs , 48 pairs were concordant in which patient of the pair evinced the same outcome factor : 43 showed no rejection after , and 5 showed one . ( ABSTRACT TRUNCATED AT 400 WORDS Cytomegalovirus is a major viral pathogen in patients who undergo renal transplantation , and cytomegalovirus disease is difficult to treat . We therefore conducted a r and omized , placebo-controlled , double-blind trial of acyclovir for the prevention of cytomegalovirus disease in recipients of renal allografts from cadavers .  Acyclovir was given orally in doses of 800 to 3200 mg per day , according to the patients ' estimated level of renal function . Patients took the first dose of either acyclovir or placebo 
    Output:
    
Prophylactic approach is superior to pre-emptive approach in preventing CMV infection within the first year of kidney transplant .
The risk of developing acute rejection is also lower with prophylactic approach in the first year of transplant but there is no significant difference in graft loss or mortality with either approach