Cheuk, D.K., Chiang, A.K., Lee, T.L., Chan, G.C., & Ha, S.Y. (2011). Vaccines for prophylaxis of viral infections in patients with hematological malignancies. Cochrane Database of Systematic Reviews, 3, CD006505.

To determine the effectiveness and safety of viral vaccines in patients with hematologic malignancies. The primary outcome was the incidence of infection. Secondary outcomes were mortality, incidence of complications, severe viral infection, hospitalization, immune response, and adverse effects.

Databases searched were the Cochrane Central Register of Controlled Trials (CENTRAL), MEDLINE, EMBASE, and CINAHL (June 2010). In addition, reference lists of relevant articles, abstracts from scientific meetings, and contacted vaccine manufacturers were used.

Randomized, controlled trials (RCTs) evaluating viral vaccines in patients with hematologic malignancies were included. No exclusion criteria were stated.

A total of 565 references were retrieved.

Relative risk (RR) was used for binary data, and mean difference (MD) was used for continuous data. The fixed-effect model was used in meta-analyses. Two authors (first and second authors) independently reviewed titles and abstracts of references retrieved from the searches and selected all potentially relevant studies. Copies of these articles were obtained and reviewed independently by the same authors against predefined inclusion criteria. The authors were not blinded to the names of the trial authors, institutions, or journal of publication. All disagreements about the selection of studies were resolved by consensus.

Interventions evaluated included heat-inactivated varicella-zoster virus (VZV) vaccine (two trials), influenza vaccines (five trials), and inactivated poliovirus vaccine (IPV) (one trial).

• The final study sample included eight RCTs.
• Three hundred five patients were in intervention groups and 288 were in control groups.  
• Sample sizes across studies ranged from 25 to 182.
• Patients of all ages with hematologic malignancies, including acute and chronic leukemias, lymphomas (Hodgkin and non-Hodgkin), and myelomas, were included. Trials evaluating all forms of viral vaccines, including influenza, varicella, hepatitis A, hepatitis B, measles, mumps, rubella, and poliomyelitis, were included in the review. The control interventions could be placebo vaccine, no vaccine, an alternative form of vaccine, or alternative dosing regimens or schedules.

Patients were undergoing the active treatment phase of care.

The VZV vaccine might reduce herpes zoster compared with no vaccine (relative risk [RR] = 0.54; 95% confidence interval [CI] [0.3, 1.0]; p = 0.05). Vaccination also demonstrated efficacy in immune response but frequently caused local adverse effects. One trial reported a severity score of zoster that favored vaccination (MD = 2.6; 95% CI [0.94, 4.26]; p = 0.002). Two RCTs compared inactivated influenza vaccine with no vaccine and reported a lower risk of lower respiratory infections (RR = 0.39; 95% CI [0.19, 0.78]; p = 0.008) and hospitalization (RR = 0.17; 95% CI [0.09, 0.31]; p < 0.00001) in vaccine recipients. However, vaccine recipients more frequently experienced irritability and local adverse effects. There was no significant difference in seroconversion between one and two doses of influenza vaccine (one trial), or between recombinant and standard influenza vaccine (one trial), or influenza vaccine given with or without reinduction chemotherapy (one trial). The IPV trial comparing vaccination starting at 6 versus 18 months after stem cell transplantation (SCT) found no significant difference in seroconversion.

Inactivated VZV vaccine might reduce zoster severity in adult SCT recipients. Inactivated influenza vaccine might reduce respiratory infections and hospitalization in adults with multiple myeloma or children with leukemia or lymphoma. Local adverse effects occur frequently.

The quality of evidence is low.

Further high-quality RCTs are needed.