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Pertussis {whooping cough} is a bacterial respiratory infection caused by the gram-negative bacillus Bordetella pertussis. Its hallmark is a cough
illness that lasts many weeks. A related organism, Bordetella parapertussis, can produce a less severe pertussis-like syndrome. Pertussis may occur at any age {infection of adolescents and adults is increasingly recognized} but
is most severe in infants and young children.
A case definition of pertussis was developed by the World Health Organization for use in vaccine efficacy trials, but this definition eliminates some laboratory-confirmed cases from efficacy calculations. Because these cases are more common in vaccinees than in controls, vaccine
efficacy appears better than it truly is whereas less effective vaccines seem comparable with their more effective counterparts. In addition observer
bias may contribute to the appearance of enhanced efficacy of the less effective vaccines, which tend to prevent typical but not mild disease.
When analyzing efficacy based on prevention of laboratory-confirmed pertussis with cough }=7 days, single component pertussis toxin {PT} toxoid
vaccines were found to be less effective than two-component PT toxoid,filamentous hemagglutinin vaccines, and three- or four-component vaccines containing pertactin in addition to PT toxoid and filamentous hemagglutinin were more effective than either the single-component or two-component vaccines.{ 1 }
In clinical studies vaccines containing three, four or five components were more effective at preventing pertussis than vaccines containing only inactivated pertussis toxin and filamentous hemagglutinin. These data suggest that pertactin may make a contribution to the protection elicited by an acellular product. { 2 }
In several countries pertussis is re-emerging, despite a high vaccination coverage. It is suggested that antigenic divergence between Bordetella pertussis vaccine strains and circulating strains, in particular with respect to pertactin, has contributed to pertussis re-emergence.Evidence is provided for the immunological relevance of polymorphism in region 1. Region 1 was found to contain a B-cell epitope recognized in both humans and mice. Furthermore, variation in region 1 affected antibody binding and the efficacy of a whole-cell vaccine. Moreover, passive and active immunization indicated that region 1 confers protective immunity. An mAb directed against a linear conserved epitope conferred cross-immunity against isolates with distinct pertactin variants. The results indicate an important role of region 1 of pertactin in immunity. { 3 }
1. Comparative efficacy of acellular pertussis vaccines: an analysis of recent trials. Update on Pertussis and Diphtheria-Tetanus Toxoids-Pertussis Vaccination Pediatric Infectious Disease Journal. 16{4} Supplement 1:S90-S96, April 1997. CHERRY, JAMES D. MD, MSC
2. Pertussis: current concepts of pathogenesis and prevention. Update on Pertussis and Diphtheria-Tetanus Toxoids-Pertussis Vaccination
Pediatric Infectious Disease Journal. 16{4} Supplement 1:S78-S84, April 1997. HEWLETT, ERIK L. MD
3. Role of the polymorphic region 1 of the Bordetella pertussis protein pertactin in immunity. Audrey J. King, Guy Berbers, Hans F. L. M. van Oirschot, Peter Hoogerhout, Karen Knipping and Frits R. Mooi, Microbiology {2001}, 147, 2885-2895.
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· Diphtheria-tetanus-acellular pertussis {DTPa} vaccines have also ensured continued high level disease protection in these countries following the shift from Pw- to Pa-containing vaccines, and allowed pertussis booster programs to be implemented. Vaccines containing between one and five components have been licensed and implemented. Those with three or more components consisting of filamentous hemagglutinin {FHA}, pertussis toxin {PT} and pertactin {PRN} are considered to be more effective than one-two-component Pa vaccines that contain only PT or both PT and FHA. Data obtained from a DTPa5 vaccine containing FIM2 and FIM3 have indicated a shift towards an increase in FIM3-expressing B. pertussis clinical breakthrough cases when compared with control vaccine. By contrast, relatively minor PT and PRN sequence polymorphisms have been identified adsorption of PRN to aluminum salt appears critical for optimal protective capacity in pertussis lung challenge.
· In addition, clinical studies have shown anti-PRN antibody levels to be higher when PRN is adsorbed.The available data, therefore, demonstrate that appropriately formulated acellular vaccines containing PT and PRN are the preferred option for pertussis immunization. { 1 }
· In several countries pertussis is re-emerging, despite a high vaccination coverage. It is suggested that antigenic divergence between Bordetella pertussis vaccine strains and circulating strains, in particular with respect to pertactin, has contributed to pertussis re-emergence. Moreover, passive and active immunization indicated that region 1 confers protective immunity. An mAb directed against a linear conserved epitope conferred cross-immunity against isolates with distinct pertactin variants. The results indicate an important role of region 1 of pertactin in immunity. { 2 }
REFERENCES:
1. Acellular pertussis vaccines and the role of pertactin and fimbriae.
Poolman JT, Hallander HO. Expert Rev Vaccines. 2007 Feb,6{1}:47-56
2. Role of the polymorphic region 1 of the Bordetella pertussis protein pertactin in immunity
Audrey J. King1,4, Guy Berbers2, Hans F. L. M. van Oirschot1, Peter Hoogerhout3, Karen Knipping2 and Frits R. Mooi1,4 Microbiology {2001}, 147, 2885-2895.
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The preventive healthcare in paediatrics is forever innovating and newer and better modalities are available to the clinician. The clinician though is regularly bombarded by marketing jargon and only exposed to half-baked information from the various sources. This has led to more confusion and
improper utilization of available products. The scientific CME's has always been in the forefront of updating the clinician with recent advances and developments in this sector. In-spite of this, the percolation of scientific information and guidelines have always been confusing and mixed.
The most recent in the series has been the launch and science related to the acellular pertussis vaccine. The pediatrician should dissect the depth of the issue and subvert a long and avoidable crisis in the immunization of the
generation next.
A few debatable points that may be considered would concern
1. Importance of various components in the vaccine?
2. Importance of pertactin presence or absence in any vaccine?
3. Re-emergence of Hib disease ever since acellular vaccine has been advocated in the west?
4. Increase in clinical and symptomatic cases of para-pertussis in adolescents and adults?
5. Withdrawal of 2 component vaccine in the west and introduction of the same in INDIA?
It would be of prime importance that all available scientific data is well examined and all pediatricians across India are informed of the most suitable vaccine for vaccinating our infants in future. The guidelines would also help simplifying the schedule,which would reduce the existing and
"unknown confusion" amongst practicing pediatricians.
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