Residual risk estimates for transfusion-transmissible infections

Australia has one of the safest blood supplies in the world in terms of viral safety. The Australian Red Cross Blood Service publishes estimates of the residual risks of transfusion-transmissible infection as a guide for clinicians in transfusion decision-making and informed consent processes.

The Blood Service residual risk estimates for transfusion-transmissible viral infections represent median risk estimates and have been derived using four published models.

Risks of transfusion-transmissible infection calculated on Blood Service data

Agent and testing standard Window period Estimate of residual risk ‘per unit' (a)
HIV (antibody/p24Ag + NAT) 5.9 days Less than 1 in 1 million(1)
HCV (antibody + NAT) 2.6 days Less than 1 in 1 million(1)
HBV (HBsAg + NAT) 15.1 days Less than 1 in 1 million(1,4)
HTLV 1 & 2 (antibody) 51 days Less than 1 in 1 million(1)
vCJD [No testing]   Possible, not yet reported in Australia
Malaria (antibody) 7–14 days Less than 1 in 1 million(2)

Notes: vCJD=variant Creutzfeldt-Jakob Disease; (a) The risk estimates for HIV, HTLV and HCV are based on Blood Service data from 1 January 2013 to 31 December 2014. As no HTLV incident donors were recorded for the period, the residual risk estimate was derived from one model only and based on first-time donor risk calculation. The HBV WP and OBI risk function have been estimated using Blood Service data from 1 January 2014 to 16 April 2015.(4)

These estimates are updated annually. Estimates are conservative since they are based on the ‘worst case’ assumption that an infectious donation is always issued for transfusion, and that if transfused, will always lead to infection in the recipient (ie infectivity is 100%). There are factors which may mitigate the risk of transmission including the volume of plasma in the component transfused, the number of viral particles per unit volume and the immune status of the recipient.

The relative risks of transfusion transmitted viral infections are very small compared to the health risks of everyday living (refer Relative risk of transfusion chart).

There have been no reported cases of transmission by transfusion of classical Creutzfeldt-Jakob Disease (cCJD), and retrospective studies suggest that the possibility of such transmission of cCJD is remote. (3)

To date there have been no reported cases of vCJD in Australia. In the UK, there have been a small number of reported cases of putative transfusion transmission since 2004.

In Australia, as a precaution, people who have spent a cumulative period of 6 months in the UK between 1 January 1980 and 31 December 1996 and/or had a transfusion in the UK between 1 January 1980 and the present time are not accepted as blood donors.



  1. Seed CR, Kiely P, Keller AJ. Residual Risk of Transfusion Transmitted Human Immunodeficiency Virus, Hepatitis B Virus, Hepatitis C Virus and Human T Lymphotrophic Virus. Internal Medicine Journal 2005;35(10):592–598.
  2. Seed CR, Kee G, Wong T, Law M, Ismay S. Assessing the safety and efficacy of a test based, targeted screening strategy to minimise transfusion transmitted malaria. Vox Sang 2010;98:e182–192.
  3. Dorsey et al. Lack of evidence of transfusion transmission of Creutzfeldt-Jakob disease in a US surveillance study. Transfusion 2009;49:977–984.
  4. Seed CR, Kiely P, Hoad VC, Keller AJ: Refining the risk estimate for transfusion-transmission of occult hepatitis B virus. Vox Sang 2016. DOI:10.1111/vox.12446