Anaphylaxis as an adverse event following immunisation (AEFI) is a rare occurrence. We report four cases of anaphylaxis following administration of single component measles or rubella vaccine between January 2003 and June 2007. We estimate that the incidence of anaphylaxis to measles and rubella single component vaccines is 18.9 and 22.4 cases/100 000 doses, respectively. These figures are likely to be an underestimate but are higher than expected. Our calculations were hampered by lack of immunisation reporting data from the private sector. We recommend that NHS standards of vaccine data reporting are also applied to private clinics.
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Anaphylaxis is a rare adverse event following immunisation (AEFI). The incidence for all vaccines has been estimated at 0.65/million doses based upon five individual cases in over 7 million doses of vaccine.1 The combined measles, mumps and rubella vaccine (MMR) has been used in the UK since 1988. The best national estimate of the incidence of anaphylaxis for the MMR was 1.4 cases/100 000 doses (two cases of anaphylaxis in 143 000 doses).2
In 1998 public confidence in the MMR waned following media speculation about its safety (www.mmrthefacts.nhs.uk), and some parents opted for single component vaccines from private healthcare providers in the belief that this might be safer. Between 2000 and 2002 an estimated 5.2% of UK children were immunised using single antigen vaccines.3 These vaccines are not licensed for use in the UK and require an import licence from the Medicines and Healthcare products Regulatory Agency (MHRA). Four cases of anaphylaxis were referred to us following administration of single component measles and rubella vaccines between January 2003 and June 2007, and we estimate the incidence of anaphylaxis to these vaccines. These were the only cases of anaphylaxis following immunisation referred during this period. All met the Brighton Collaboration case definition for anaphylaxis AEFI.4 Clinical details are given in table 1. We have parental permission to report three cases in detail.
We were unable to establish the actual number of doses of single component vaccines administered in the UK as there is no central reporting. Unlike standard schedule vaccines in NHS primary care, private clinics are under no obligation to report the number of unlicensed vaccines administered. However, information on the number of requests for import was available from the MHRA. Based on the assumption that all imported vaccine was administered, we calculated an incidence of anaphylaxis for measles vaccine of 18.9 cases/100 000 doses (95% CI 5.2 to 68.9) and 22.4 (6.1 to 81.6) for rubella.
These rates appear to be well above those expected for the MMR but are still likely to be an underestimate. We have assumed that these four children were the only cases of anaphylaxis nationally, and that all MHRA requested vaccine was used, when in reality there may have been other cases around the country and only 20–30% of imported vaccine may actually be administered.5
Post licensure surveillance requires both active reporting of AEFI by healthcare professionals and comprehensive recording of the number of vaccine doses administered. We add our voices to the recommendation that the Healthcare Commission insists that private clinics are subject to the same standards of vaccine data reporting as are expected of the NHS.5
The authors would like to thank Graham Matthews of the Export Certificates and Unlicensed Imports Group, and the Pharmacovigillance Unit at the MHRA for help in supplying data for the preparation of this manuscript.
Competing interests: MEL has accepted support to attend and present data at scientific meetings from Wyeth and GlaxoSmithKline, and has received research funding from Sanofi Pasteur MSD, the makers of Rudivax and Priorix MMR. AF has undertaken advisory work for, chaired and spoken at symposia organised by and accepted support to attend scientific meetings from all the major vaccine manufacturers. Payments for these activities have been made to his employer, the University of Bristol and used to pay for research and training materials and activities. RM, RL and AE have no conflict of interest to declare.
Patient consent: Obtained.
Contributors: MEL is the guarantor for this paper. MEL and RM wrote the paper. RL provided background research for the paper. All authors were involved in developing and editing the manuscript.
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