The authors concluded that chemotherapy in children with acute lymphocytic leukaemia is associated with a temporary reduction in antibody levels against specific diseases and re-vaccination may be required. The evidence was based on a very small number of children in few studies and the results varied widely across studies. This suggests that a more cautious conclusion might be appropriate.

To review the vaccination and re-vaccination status of children who have been treated for acute lymphocytic leukaemia (ALL).

PubMed and EMBASE were searched from January 1980 to January 2006 for peer-reviewed studies published in the English language after 1980. The search strategy was reported. In addition, reference lists in identified reports were screened, a 'related articles' search was undertaken, and ISI Web of Knowledge was scanned.

Studies with at least 10 children per vaccine group were eligible for inclusion. Studies in which subgroups of less than 10 children had been re-vaccinated were excluded from the analysis. No other inclusion criteria were specified for study design.

Studies of (re-)vaccination were eligible for inclusion. The review evaluated (re-)vaccination with the following vaccines: diphtheria, pertussis, tetanus, poliomyelitis (three serotypes), haemophilus influenza type B (HIB), mumps, measles and rubella.

Studies of children aged younger than 18 years who had been treated for ALL were eligible for inclusion. Studies of children who were still receiving chemotherapy were excluded. The included studies were conducted between 1973 and 2002.

Studies that reported the vaccination status of children in such a way that the percentage of protected children could be calculated were eligible for inclusion. The review assessed the percentage of children with protection before chemotherapy and after re-vaccination. The included studies varied in the timing of assessment of vaccination status post-chemotherapy (where reported, range: 0 to 168 months) and in the definition of the antibody level that was considered protective (details of levels used in the individual studies were reported, where possible, for each vaccine type).

Two reviewers independently selected the studies. Any disagreements were resolved by discussion.

The authors did not state that they assessed validity.

The authors did not state how the data were extracted for the review, or how many reviewers performed the data extraction.

Where possible, for each study, the percentages of children protected before and after chemotherapy and after re-vaccination were extracted and protection rates post-chemotherapy with 95% confidence intervals (CIs) were plotted graphically for each vaccine type.

The studies were grouped by vaccine type and the range of protection across studies was reported.

Differences between the studies were discussed.

Eight studies (n=340) were included. Some studies reported data from different numbers of children for different vaccine types.

Few studies reported pre-chemotherapy protection rates.

Diphtheria (5 studies, n=188): 3 studies reported post-chemotherapy protection rates above 80%. The other 2 studies reported post-chemotherapy protection rates of 17% and 33%; these studies reported re-vaccination protection rates of 87% and 100%, respectively. One of these studies (with a post-chemotherapy protection rate of 17%) reported a pre-chemotherapy protection rate of 39%. Post re-vaccination rates were not reported for any other studies.

Pertussis (3 studies, n=87): no studies reported pre-chemotherapy protection rates. Post-chemotherapy protection rates ranged from 27 to 82%. One study (post-chemotherapy protection rate 34%) reported a re-vaccination protection rate of 66%.

Tetanus (6 studies, n=284): 1 study reported a pre-chemotherapy protection rate of 81% and a post-chemotherapy protection rate of 33%. Four studies reported post-chemotherapy protection rates of 69% or above. The other 2 studies reported post-chemotherapy protection rates of 33% and 20%; these studies reported re-vaccination protection rates of 77% and 100%, respectively. Post re-vaccination rates were not reported for any other studies.

Poliomyelitis (4 studies, n=173): none of the studies reported pre-chemotherapy protection rates or re-vaccination rates. Three studies reported post-chemotherapy protection levels above 70%. The other study reported post-chemotherapy protection rates ranging from 62 to 92% across the three serotypes. None of the studies reported post re-vaccination protection rates.

HIB (3 studies, n=134): 1 study reported a pre-chemotherapy protection rate of 100% and a post-chemotherapy protection rate of 100% (using a titre of 0.15 microg/mL). Two studies reported post-chemotherapy protection rates of 35% and 75%. Post-vaccination protection rates rose from 75 to 83% in 1 study and were reported as 93% in another study that reported no other rates.

Mumps (3 studies, n=132), measles (4 studies, n=176) and rubella (3 studies, n=155): the studies used different definitions of protective antibody levels. One study reported a pre-chemotherapy protection rate for measles of 15 out of 16 patients and a post-chemotherapy protection rate of 60%. The studies reported a wide variation in post-chemotherapy protection rates (range: 29 to 92%. One study reported a pre-chemotherapy protection rate for rubella of 16 out of 16 patients and a post-chemotherapy protection rate of 72%. One study reported a post-chemotherapy protection rate of 29% for mumps, which rose to 66% after re-vaccination. The same study reported a post-chemotherapy protection rate of 29% for measles, which rose to 76% after re-vaccination. Other studies did not report protection rates after re-vaccination.

Chemotherapy in children with ALL is associated with a temporary reduction in antibody levels against specific diseases and re-vaccination may be required.

The review addressed a clear question that was defined in terms of the participants, intervention, outcomes and some aspects of study design. Several relevant sources were searched but no attempts were made to minimise either publication or language bias. Methods were used to minimise reviewer error and bias in the study selection process, but it was not clear whether similar steps were taken when extracting the data. Study validity was not assessed and little information was provided about the participants.

The results were presented as ranges of values of protection rates, which seemed appropriate given the diversity of the studies. Evidence regarding the drop in level of protection after chemotherapy and protection after re-vaccination was based on a very small number of children in few studies, and the protection rates varied considerably across studies. This suggests that a more cautious conclusion might have been more appropriate. In addition, incomplete reporting of review methods meant it was not possible to assess the reliability of the review.

Practice: The authors stated that decisions regarding the screening and re-vaccination of patients after chemotherapy should take account of the local situation (level of vaccination coverage and level of disease).

Research: The authors stated the need for larger, multicentre, prospective longitudinal studies to evaluate the effect of current ALL treatment regimens on immunity and its restoration in homogeneous populations of patients.

This record is a structured abstract written by CRD reviewers. The original has met a set of quality criteria. Since September 1996 abstracts have been sent to authors for comment. Additional factual information is incorporated into the record. Noted as [A:....].