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Increasing notification rates for invasive meningococcal disease (IMD) in Australia (Commun Dis Intell 2001;25: 126-129) justify consideration of new immunisation strategies including the use of meningococcal serogroup C conjugate (MCC) vaccine. Such a strategy has been deployed with great effect in the United Kingdom and the Republic of Ireland over recent years.
The juxtaposition of two statements in your editorial 'a 25 per cent increase in serogroup B disease across all age groups in the United Kingdom' and 'this observation supports a hypothesis that serogroup replacement may be an important factor in the epidemiology of meningococcal disease' suggests that there is concern that the MCC vaccination campaign in the UK has been in some way responsible for serogroup replacement and increasing IMD. There is no such concern. There is no evidence that serogroup replacement is occurring.
According to Dr Ed Kaczmarski from the Public Health Laboratory Service (PHLS) and the Meningococcal Reference Unit, careful surveillance for evidence of serogroup replacement is in place and so far there is no evidence of this occurring. Concerns that the prevention of serogroup C disease by vaccination might result in a capsular switch to serogroup B remain entirely speculative.1
To date there have been 1,204 cases in all age groups of IMD due to serogroup B notified to the PHLS this year compared with a total of 1,645 in 2000.2 For serogroup C the numbers are 255 and 712 respectively, although the cases now are largely in age groups which have not been vaccinated. Archival data can be viewed showing the dramatic decline in serogroup C disease in England and Wales,3 and in Scotland.4
In the Republic of Ireland an overall 28 per cent decrease in IMD notifications occurred in 2000 to 2001 in comparison with the previous year.5 The incidence of group B IMD dropped by 14.4 per cent to 6.5 per 100,000 population in 2000 to 2001 from 7.6 per 100,000 population in 1999 to 2000 and there are no indications to date that the incidence of IMD due to non-B, non-C serogroups is increasing.
Any epidemiological or molecular evidence of 'vacuum filling', capsular switching or serogroup replacement will appear rapidly in the public domain. Meningococcal serogroup B and other serogroup vaccines are under development for the purpose of building on the successes of existing meningococcal immunisation programmes. The reader's attention should be drawn to a forthcoming editorial by John Tapsall to appear in the Journal of Paediatrics and Child Health which addresses the Australian situation more particularly and the forthcoming Proceedings of the 41st ICAAC which will address the global imperatives for meningococcal immunisation.
Dr E. David G. McIntosh
Senior Medical Adviser, Wyeth
References1. Miller E, Salisbury D, Ramsay M. Planning, registration, and implementation of an immunisation campaign against meningococcal serogroup C disease in the UK: a success story. Vaccine 2001; 20 Suppl 1:S58-S67.
5. Fitzgerald M, O'Flanagan D, Cafferkey M, Murphy K. Invasive meningococcal disease in Ireland 2000/2001. Epi-Insight 2001;2:2-3.
This article was published in Communicable Diseases Intelligence Volume 25, No 4, November 2001.