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 have been derived using published models and are updated periodically.

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 [1,2]
HCV (antibody + NAT) 2.6 days Less than 1 in 1 million [1,2]
HBV (HBsAg + NAT) 15.1 days Less than 1 in 1 million [1-3]
HTLV 1 & 2 (antibody) 51 days Less than 1 in 1 million (b)
vCJD [No testing]   Possible, not yet reported in Australia
Malaria (antibody) 7–14 days Less than 1 in 1 million [4]


vCJD = variant Creutzfeldt-Jakob Disease
(a) HIV, HCV and HBV WP risk estimates are based on Blood Service data from 1 January 2015 to 31 December 2016. HBV OBI risk based on Blood Service data from 1 July 2016 to 30 June 2017.
(b) No HTLV incident donors recorded for the period – residual risk estimate derived from single model using first-time donor calculation and based on Blood Service data from 1 January 2015 to 31 December 2016.

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 [5].

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. Intern Med J 2005;35(10):592–598.
  2. Weusten J, Vermeulen M, van Drimmelen H, et al. Refinement of a viral transmission risk model for blood donations in seroconversion window phase screened by nucleic acid testing in different pool sizes and repeat test algorithms. Transfusion 2011;51:203-215.
  3. Seed CR, Kiely P, Hoad VC, Keller AJ: Refining the risk estimate for transfusion-transmission of occult hepatitis B virus. Vox Sang 2017;112(1):3-8.
  4. 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.
  5. Crowder LA, Schonberger LB, Dodd RY, Steele WR. Creutzfeldt-Jakob disease lookback study: 21 years of surveillance for transfusion transmission risk. Transfusion. 2017 Aug;57(8):1875-8.