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Tuesday, 7 February 2012

Pertussis - is it time to consider more adult protection?

PHAC reports 1-3 infant deaths from pertussis annually in Canada. An equal number suffer irreparable brain damage from anoxic spells.  Not a massive amount, however certainly beats the impacts of tetanus and diphtheria. 

The rather dated PHAC information in the chart shows the overall incidence of pertussis in Canada over decades, with recent incidences of 2000-10000 cases annually.   

Despite tremendous gains in protecting infants, the current immunization strategy is somewhat short and requires some difficult questions to be asked.
First and foremost is the need for primary immunization of infants at a time where some parents are barraged with information on the risks of immunization.  Choices to avoid or defer infant immunizations put the very children at the highest risk of severe illness.   The failure to immunize amongst closely knit communities accentuates the risk within those communities should illness get established.

Herd immunity has clearly been a benefit nationally.  Secondary vaccine failure and the lack of persistent protection may be setting the stage for a future dangerous storm.  Breakthrough outbreaks are continuing to occur and should be a warning sign. Adult pertussis is being more frequently diagnosed, and likely increasing in incidence although surveillance is meager at best.  

Serious consideration needs to be given to the question of whether the adult Td (tetanus diphtheria) booster should be replaced with the TdaP (including ‘acellular’ pertussis vaccine) in routine adult immunization programs.   The current recommendations are for a single dose of acellular pertussis after the preschool/kindergarten vaccination, this is generally provided in Grades 7-9 (depending on province).  
Of course, trying to get accurate costs on the cost differential between the vaccines is challenging and guarded in business secrecy, however the differential may well warrant the shift.  

Recent outbreaks have punctuated the importance of both unimmunized children and adults as vectors in dissemination of illness.   As NACI meets this week, perhaps a topic for consideration?   While we are at it, it would be nice to have NACI minutes and actions posted for increased transparency in the decision processes NACI home site 

Addendum:  Please see the comment from NonStopGO.  The posting is a reflection of the knowledge the issue is one for debate and several strategies are being promoted - however the discussion has not engaged the general public health community in a meaningful fashion.  Using adult immunization is already being utilized for outbreak control in some settings. Thanks Nonstop  

1 comment:

  1. Good post Dr. P... There are more recent developments in this, such as the CCDR posting (http://www.phac-aspc.gc.ca/ccdrw-rmtch/2011/ccdrw-rmtcs0111-eng.php) on the CID article by Healy et al http://cid.oxfordjournals.org/content/52/2/157.abstract
    and the subsequent article in CID by Skowronski CID 2012:54 (1 February) ... I think the debate on this issue is still out and clearly requires detailed epidemiology on incidence rates to make the intervention effective.
    Perhaps targetted cocooning??