Replacement: Difference between revisions

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Serotype replacement means the replacement of the serotypes in the vaccine with serotypes that aren't included in the vaccine. In a vaccinated population the replacement has usually happenes fairly fast after the beginning of the vaccination program. Because of serotype replacement the vaccine against the desease has been less efficient than expected. Nurhonen and Auranen have built a model [http://www.ploscompbiol.org/article/info%3Adoi%2F10.1371%2Fjournal.pcbi.1003477], that describes the mechanism of replacement in a vaccinated population. With the model it is possible to calculate estimates for the effects of different serotype combinations in vaccines against pneumococcal disease incidences in a population and find the serotypes that it would be most effective to add to current vaccinations in order to avoid invasive pneumococcus infections.
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[[File:Replacementchart.png|thumb|center|600px|alt= graph of effects of vaccine|Pneumococcus carriage (on x-axis) and incidences per carriage (on y-axis) for serotypes in vaccine (VT) and serotypes the vaccine does not effect (NVT) before the vaccination program (chart A) and after (chart B). Incidences (DNVT and DVT) are a result of multiplying the values on the axes and are displayed as a rectangular areas. The carriage of serotypes in vaccines has been divided into three sections according to the effect of carriage in a population: (i) Carriage removed by vaccine changed into another carriage (VT*pq); (ii) Carriage removed by vaccine and not replaced by new carriage (VT*(1-p)q); (iii) Carriage not removed by vaccine (VT*(1-q)). In this chart q is carriage removed by vacccine and p is is carriage removed by vaccine and replaced by new carriage not included in the vaccine's serotypes. The incindences decrease because of the difference in virulency of the the removed and replaced carriage. The disappearence of incidences is shown as a blue rectangle (chart B).]]
Serotype replacement means the replacement of the serotypes in the vaccine with serotypes not included in the vaccine. In a vaccinated population the replacement usually happenes reasonably soon after the beginning of the vaccination program. Because of serotype replacement, vaccine effectiveness against invasive disease has been milder than expected. Nurhonen and Auranen have built a model [http://www.ploscompbiol.org/article/info%3Adoi%2F10.1371%2Fjournal.pcbi.1003477], that describes the mechanism of replacement in a vaccinated population. Using the model it is possible to calculate predicted effects of different serotype combinations in a conjugate vaccine against pneumococcal disease in a population and find the serotypes that would be most beneficial additions to current vaccine compositions to prevent invasive pneumococcus disease.
 
 
[[File:Model_kuva_simplified2.jpg|thumb|center|600px|'''Figure 1. Illustration of the replacement model.''' The incidence of pneumococcal carriage (x-axis) and case-to-carrier ratios (y-axis) for vaccine serotypes (VT) and non-vaccine serotypes (NVT) before (panel A) and after vaccination (panel B). The incidences of disease (DVT and DNVT) are obtained by multiplication of the two quantities and correspond to the areas of the rectangles. After vaccination, VT carriage is eliminated and replaced by NVT carriage (panel B). The decrease in IPD incidence after vaccination is obtained as the difference between the eliminated VT disease and the replacing NVT disease. This is the area of the blue rectangle in panel  B.]]


== See also ==
== See also ==


{{pneumococcal vaccine}}
{{pneumococcal vaccine}}

Latest revision as of 13:22, 21 August 2014


Serotype replacement means the replacement of the serotypes in the vaccine with serotypes not included in the vaccine. In a vaccinated population the replacement usually happenes reasonably soon after the beginning of the vaccination program. Because of serotype replacement, vaccine effectiveness against invasive disease has been milder than expected. Nurhonen and Auranen have built a model [1], that describes the mechanism of replacement in a vaccinated population. Using the model it is possible to calculate predicted effects of different serotype combinations in a conjugate vaccine against pneumococcal disease in a population and find the serotypes that would be most beneficial additions to current vaccine compositions to prevent invasive pneumococcus disease.


Figure 1. Illustration of the replacement model. The incidence of pneumococcal carriage (x-axis) and case-to-carrier ratios (y-axis) for vaccine serotypes (VT) and non-vaccine serotypes (NVT) before (panel A) and after vaccination (panel B). The incidences of disease (DVT and DNVT) are obtained by multiplication of the two quantities and correspond to the areas of the rectangles. After vaccination, VT carriage is eliminated and replaced by NVT carriage (panel B). The decrease in IPD incidence after vaccination is obtained as the difference between the eliminated VT disease and the replacing NVT disease. This is the area of the blue rectangle in panel B.

See also

Tendering process for pneumococcal conjugate vaccine
Parts of the assessment

Comparison criteria for vaccine   · Epidemiological modelling   · Economic evaluation

Background information

Sensitivity analysis · Replacement   · Pneumococcal vaccine products   · Finnish vaccination schedule   · Selected recent publications

Help for discussion and wiki editing

Pages in Finnish

Pneumokokkirokotteen hankinta  · Rokotteen vertailuperusteet · Epidemiologinen malli · Taloudellinen arviointi · Pneumokokkirokotteen turvallisuus

Work scheduling · Monitoring the effectiveness of the pneumococcal conjugate vaccine · Glossary of vaccine terminology


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