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Opinions : HAEMOPHILUS INFLUENZA TYPE B VACCINE – PERSONAL THOTS
Our HiB national immunization campaign is well underway. MPA has put together a roadshow to update doctors on the “new kid” on the immunization bloc i.e. MMR and HiB. Quite evidently (and from private conversations with colleagues in the MOH), our HiB programme is very much patterned along those of the UK. Three jabs accelerated at 2,3,5 months with no booster dose. Early priming is appropriate for the epidemiology of HiB invasive disease in our country but the lack of boosting is however worrisome. I believe many colleagues in private practice adopt similar strategies and those in affluent communities offer the combined DTaP-Hib with OPV and most would also offer the booster dose.
I hold dearly to my current view on the use of IPV (at least for the initial 2 doses; and hence the type of combos available ) and my refusal to entertain HiB combinations which significantly depress HiB antibody titres. In this context I am as recalcitrant as the FDA vis a vis new DTaP-HiB combinations .The induction of “immunological memory against HiB” hypothesis as a premise for adequate clinical protection despite dipping HiB GMT is much disputed. Notwithstanding, virtually all advocates of DTaP-HiB combinations who subscribe to the concept of high quality antibody and immune memory adds the important proviso that careful clinical surveillance of HiB disease should be maintained (1).
Close collaboration between UK paediatricians, microbiologists and public health physicians has allowed active national surveillance of HiB disease and enabled important conclusions to be drawn (2). I hope a HiB surveillance program is similarly activated in our local context - another MPSU project ?
The recent 4 years has actually seen a rise in the incidence of HiB disease in the UK, from 0.65 per 100,000 in 1998 to 4.6 per 100,000 in 2002 (3). The reasons are multifactorial but featuring very significantly is the temporary usage of a DTaP – HiB combo. Analysis of the data from the UK shows a significant association between the DTaP-HiB combo and breakthrough invasive HiB disease. Coupled with the 2,3,4 months schedule used in the the UK, the lower immunogenicity of the combo is clinically relevant (4).
The use of DTwP-HiB vaccines has been resumed and a booster dose is now recommended by the Chief Medical Officer (5).
Without sounding an alarmist how could this “not unexpected” revelation affect our local practice ? How could one still use acellular pertussis (sorry for being private sector biased ) without compromising HiB disease containment?
- Administer HiB separately which is quite clearly not child friendly!
- I am aware of at least one DTaP-HiB combo which does not have a suppressive effect on the HiB component. First used in Canada since 1997 there have been various studies to validate this non-interaction between the aP and HiB entities (6,7). And even better still, I look forward to the licensing of the aforementioned 5 component vaccine, DTaP-HiB-IPV, which affords me my “gold standard” of offering IPV and aP without any worry of jeopardizing HiB control and all in 1 shot ! This to me seems to be the best option. I hope the “powers that be” (read as “certain colleagues in the MOH” ) will not once again deny me ( I cannot claim to speak for other colleagues in the private sector ) my right to best practice in evidence based vaccinology.
- Scheduling may affect immunological response. Further distancing between injections may lessen the suppression on HiB response in acellular combos. A rather tedious public health option though considering we’ve only just adjusted our schedule after a long hiatus! Epidemiologically, the earlier age of onset of disease in our population does not render this a tenable option.
- A booster dose is quite clearly in order. Cost considerations has led to the trimming of the number of HiB doses which has turned to be an English folly !
References
- Eskola J et al.Randomised trial of the effect of co-administration with DTaP on immunogenicity of HiB conjugate vaccine. Lancet 1996;348:1688-1692
- PT Heath et al. The UK HiB vaccine experience. Arch Dis Child 2002; 86:396-399
- HiB vaccine - booster campaign. Editorial BMJ Vol 326, 31 May 2003
- J McVernon et al. Risk of vaccine failure after HiB combination vaccines with acellular pertussis. Lancet 2003; 361:1521-1523
- Department of Health UK. Planned HiB vaccination catch-up campaign. 17th Feb 2003
- Chin Yun Lee et al. An evaluation of the safety and immunogenicity of a five component acellular pertussis, diptheria and tetanus toxoid vaccine ;
(DTaP) when combined with a HiB - Tetanus Toxoid conjugate vaccine
(PRP-T) in Taiwanes infants. Pediatrics Vol 103 No 1 January 1999
- Mills E et al. Safety and immunogenicity of a combined 5 component pertussis-diptheria-inactivated poliomyelitis-HiB conjugate vaccine administered to infants at 2,4,6 months of age. Vaccine 1998;16:576-85
Musa Mohd. Nordin
Damansara Specialist Hospital
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articles from 60's-70's |
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