PALIVIZUMAB PROPHYLAXIS OF RESPIRATORY SYNCYTIAL VIRUS INFECTION IN HIGH-RISK INFANTS: A NOTE OF CAUTION

Authors


5 June 2003

Dear Editor,

PALIVIZUMAB PROPHYLAXIS OF RESPIRATORY SYNCYTIAL VIRUS INFECTION IN HIGH-RISK INFANTS: A NOTE OF CAUTION

We read with interest the article by Vogel et al. regarding respiratory syncytial virus (RSV) monoclonal antibody prophylaxis1. We would like to raise a few issues that are relevant to this article. First, the RSV infection rate that is reported in the literature is between 5 and 17%, both from studies in the UK and USA2−4. Over the past 2 years (January 2001−April 2003), our unit has cared for 61 infants (gestation range 24−32 weeks, median 26 weeks) with chronic neonatal lung disease/bronchopulmonary dysplasia (BPD) on home oxygen therapy. Over this time period, the RSV infection rate was 14.8% (9/61), with a hospitalization rate of 9.8% (6/61). The infection rate and hospitalization figures5 for the New Zealand cohort appear significantly different. There are probably multiple reasons for this (geography, weather, housing, general virulence of virus strains). Second, the cost-effective analysis calculated is based on the local infection and readmission rates. The Impact study6 percentages have been used to derive the number needed to treat (NNT) of 6 for the BPD group. Our experience is different and the equivalent calculations would result in a NNT of 30 to achieve the 39% reduction reported in the Impact study (Table 1).6

Table 1.   Calculations based on Impact6 criteria of relative-risk reduction of 39% for BPD infants
Control eventrate (%)Experimentalevent rate (%)Absolute riskreduction (%)NNTCost/case prevented from hospitalization
  1. BPD, Bronchopulmonary dysplasia; NNT, number needed to treat.

9.86.53.330$NZ143 000

Finally, the benefit of RSV prophylaxis in an Australian intensive care setting has been reviewed and no significant cost benefits were found7. Our south-east Queensland data also suggest that the BPD cohort do not show a cost benefit on the model applied in the Vogel et al. article.

In the article by Vogel et al., it may be useful to note that in the comparison of international recommendations, the UK guidelines quote from the manufacturer8 and not from a peer reviewed article9.

The recommendations that are put forward by Vogel et al. are justified for the New Zealand population but should not be generalized to the Australian population. Currently available evidence concerning the cost-benefit of palivizumab does not support its use in the Australian population of infants with BPD discharged home on supplemental oxygen therapy. Until such evidence becomes available (ideally a well-designed cost-effectiveness trial specifically for the Australian population) the use of palivizumab has to be a clinical decision taken on a patient-to-patient basis.

Ancillary