Over the past decades, the risk of HBV transfusion–transmission has been steadily reduced through the recruitment of volunteer donors, the selection of donors based on risk-behavior evaluation, the development of increasingly more sensitive hepatitis B antigen (HBsAg) assays, the use of hepatitis B core antibody (anti-HBc) screening in some low-endemic countries, and the recent implementation of HBV nucleic acid testing (NAT). Despite this accumulation of blood safety measures, the desirable zero risk goal has yet to be achieved. The residual risk of HBV transfusion–transmission appears associated with the preseroconversion window period and occult HBV infection characterized by the absence of detectable HBsAg and extremely low levels of HBV DNA. Infected donations tested false-negative with serology and/or NAT still persist and derived blood components were shown to transmit the virus, although rarely. Questions regarding the apparent redundancy of some safety measures prompted debates on how to reduce the cost of HBV blood screening. In particular, accumulating data strongly suggests that HBsAg testing may add little, if any HBV risk reduction value when HBV NAT and anti-HBc screening also apply. Absence or minimal acceptable infectious risk needs to be assessed before considering discontinuing HBsAg. Nevertheless, HBsAg remains essential in high-endemic settings where anti-HBc testing cannot be implemented without compromising blood availability. HBV screening strategy should be decided according to local epidemiology, estimate of the infectious risk, and resources.

The risk of transfusion-associated transmission of SARS-CoV-2 is unknown. Cappy and colleagues report on hemovigilance studies of 268 blood donations from individuals reporting symptoms shortly after donation. Of 268 samples, 3 tested positive for viral RNA, of which 1 had components that were transfused before testing; no cases of transfusion-documented transmission were seen.

Absence of anti‐HBc reactivity with detectable anti‐HBs was observed in blood donors with occult hepatitis B virus (HBV) infection (OBI). The prevalence and mechanisms underlying this uncommon condition were investigated over time in Chinese blood donors with OBI. Isolated anti‐HBs OBI status was identified from 466,911 donors from Dalian, China, and monitored in follow‐up (range: 2.6–84.3 months). HBV vaccination status was documented, and infecting viral strains were characterized. Of 451 confirmed OBIs (1:1035), 43 (9.5%; 1:10,858) had isolated anti‐HBs as only serological marker. Isolated anti‐HBs OBIs differed from anti‐HBc‐reactive OBIs by significantly younger age (median 24 years), higher HBV DNA (median: 20 IU/ml) and anti‐HBs (median 60.5 IU/L) levels, paucity of mutations in HBV Core and S proteins, and high vaccination rate (72%). Vaccinated isolated anti‐HBs OBIs (n = 31) differed from unvaccinated (n = 11) by significantly younger age (22 vs 38 years), higher anti‐HBs level at index (48% vs 9% with anti‐HBs >100 IU/L) and higher frequency of anti‐HBs immune response (44% vs 20%). Of 15 vaccinated and 5 unvaccinated OBIs follow‐up, 65% (8 vaccinated and 5 unvaccinated) became HBV DNA negative suggesting aborted recent infection, while 35% (7 vaccinated) had low persistent viraemia 2 to 65 months post index. In conclusion, isolated anti‐HBs OBI in Chinese blood donors appears associated with young, vaccinated, adults exposed to HBV who predominantly develop low level aborted infection revealed by transient HBV DNA and immune anti‐HBs response. However, a subset of individuals still experienced low but persistent viral replication whose clinical outcome remains uncertain.

Background: Hepatitis B core antibody (anti‐HBc) screening has been implemented in many blood establishments to help prevent transmission of hepatitis B virus (HBV), including from donors with occult HBV infection (OBI). We review HBV screening algorithms across blood establishments globally and their potential effectiveness in reducing transmission risk.Materials and Methods: A questionnaire on HBV screening and follow‐up strategies was distributed to members of the International Society of Blood Transfusion working party on transfusion‐transmitted infectious diseases. Screening data from 2022 were assimilated and analyzed.Results: A total of 30 unique responses were received from 25 countries. Sixteen respondents screened all donations for anti‐HBc, with 14 also screening all donations for HBV DNA. Anti‐HBc prevalence was 0.42% in all blood donors and 1.19% in new donors in low‐endemic countries; however, only 44% of respondents performed additional anti‐HBc testing to exclude false reactivity. 0.68% of anti‐HBc positive, HBsAg‐negative donors had detectable HBV DNA. Ten respondents did universal HBV DNA screening without anti‐HBc, whereas four respondents did not screen for either. Deferral strategies for anti‐HBc positive donors were highly variable. One transfusion‐transmission from an anti‐HBc negative donor was reported.Discussion: Anti‐HBc screening identifies donors with OBI but also results in the unnecessary deferral of a significant number of donors with resolved HBV infection and donors with false‐reactive anti‐HBc results. Whilst confirmation of anti‐HBc results could be improved to reduce donor deferral, transmission risks associated with anti‐HBc negative OBI donors must be considered. In high‐endemic areas, highly sensitive HBV DNA testing is required to identify infectious donors.