Background: The role of iatrogenic transmission within the HIV/AIDS pandemic remains contentious. Estimates of the risk of HIV transmission from injections and blood transfusions are required to inform appropriate prevention policy.
Objectives: Systematic review and meta-analysis of the literature on HIV-1 infectivity for parenteral transmission and blood transfusion.
Review methods: All identified studies with relevant transmission probability estimates up to May 2005 were included.
Statistical methods: When appropriate, summary estimates for accidental percutaneous and blood product exposures were derived.
Results: Infectivity estimates following a needlestick exposure ranged from 0.00 to 2.38% [weighted mean, 0.23%; 95% confidence interval (CI), 0.00-0.46%; n = 21]. Three estimates of infectivity per intravenous drug injection ranged from 0.63 to 2.4% (median, 0.8%); a summary estimate could not be calculated. The quality of the only estimate of infectivity per contaminated medical injection (1.9-6.9%) was assessed. Instead we propose a range of 0.24-0.65%. Infectivity estimates for confirmed contaminated blood transfusions range from 88.3 to 100.0% (weighted mean, 92.5%; 95% CI, 89.0-96.1%; n = 6).
Conclusions: Infectivity estimates for infected blood transfusions are larger than for other modes of HIV transmission. Few studies on transmission risk per contaminated injection were found. However, transmission risk per needlestick injury, where needles are more likely to be rinsed or disinfected between recipients (especially for medical injections), may be representative of non-intravenous medical injections and lower than the risk from intravenous injections, which are likely to be deeper and to involve more fluids. Further work is needed to better estimate transmission probability related to contaminated injections and its likely contribution to overall HIV transmission.