VOL: 98, ISSUE: 38, PAGE NO: 51
Veronique Gibbons, BSc, RGN, is immunisation advice nurse, Natasha Crowcroft, MA, Mac, RCP, MFPHM, is consultant epidemiologist
John Edmunds, PhD, is research fellow, Public Health Laboratory Service, LondonVeronique Gibbons, BSc, RGN, is immunisation advice nurse, Natasha Crowcroft, MA, Mac, RCP, MFPHM, is consultant epidemiologist
The recent launch of a new vaccine to protect against chickenpox (Varilrix, produced by GlaxoSmithKline) has received considerable interest within the health care profession. This vaccine (along with Varivax from Aventis Pasteur) has been available for some time on a named-patient basis.
At present, there has been no change in policy or any announcement made by the Department of Health or the Public Health Laboratory Service over a change in its use. The announcement made on July 31 was a standard product launch.
Varilrix is a live attenuated vaccine (attenuation is a process of weakening the virus in such a way that it still enables the production of an immune response without producing the typical characteristics of disease). It is licensed for use in healthy adults and adolescents from the age of 13 years who have no prior varicella immunity but is not indicated for routine use in children less than 13 years old (although it can be given in specific circumstances). It is contra-indicated in immunosuppressed and pregnant or breastfeeding individuals.
The Joint Committee on Vaccines and Immunisation (JCVI) has been considering policy on who should receive varicella zoster (VZV) vaccination for some time and has advised the DoH, who will be producing guidance in the near future. Initial target groups for this new vaccine are likely to be susceptible adults who are in contact with children.
There are no plans to introduce the vaccine into the routine childhood immunisation programme, as studies have shown (Brisson et al, 2002; Thomas et al, 2002) that this might result in an increase in zoster (shingles) cases. This is because adults who are exposed to chickenpox are significantly less likely to develop shingles than those who are not. It seems that being exposed to the virus boosts the immune response, thereby delaying or preventing the development of shingles. Reducing the incidence of chickenpox via vaccination will reduce the number of adults who receive this natural boost, resulting in an increase in shingles. Since the vaccine strain, which is live, appears to be less likely to reactivate than the natural virus, the incidence of shingles should eventually fall, but computer simulations by the team at the PHLS suggest that the period of increased shingles incidence could last for 50 years. The more effectively chickenpox is controlled, the larger the increase in shingles. Since there is no way to prevent shingles in individuals who have had chickenpox (although vaccine trials are under way), public health officials are very cautious about introducing chickenpox vaccination into the routine immunisation programme.
There have been some reports (Rawson et al, 2001) indicating that more people die from chickenpox than of the other childhood vaccine-preventable diseases put together. However, these have omitted the fact that this is only because of the success of the vaccination programme in preventing deaths from the other diseases. They are therefore highly misleading.