Residual risk of transfusion-transmitted hepatitis B virus (TT-HBV) infection by NAT-screened blood components: A review of observed versus modeled infectivity from donors with window period and occult HBV infections

International review of blood donation screening for anti-HBc and occult hepatitis B virus infection

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.

Infectivity of Hepatitis B Virus Surface Antigen-Positive Plasma With Undetectable HBV-DNA: Can HBsAg Screening Be Discontinued in Egyptian Blood Donors?

Hepatitis B Virus (HBV) infectivity data were reviewed and the 50% infectious dose (ID50) was reassessed in different HBsAg-positive infection stages enabling modelling of transfusion-transmitted (TT)-HBV infection risk if HBsAg donor screening was replaced by individual donation nucleic acid amplification technology (ID-NAT). Quantitative HBsAg and HBV-DNA assays were performed against international standards to compare the ratio between potential infectious HBV virions and subviral HBsAg particles in Egyptian HBsAg-positive blood donors as well as in Japanese chimpanzee samples of known infectivity. HBV-DNA load below the quantification limit of detection was estimated against a reference standard by replicate NAT testing (n = 25). Infectivity of chimpanzee samples collected during ramp-up and declining viremic phase were tested in a human liver chimeric mice (HLCM) model and compared with published infectivity data from different HBsAg-positive infection stages. Lowest estimates of ID50 in HBsAg-positive plasma were 3-6 HBV virions in chimpanzee studies. Infectivity decreased approximately 10-100-fold in the declining viremic phase using HLCM. In acute phase samples, HBV to HBsAg particle ratios varied between 1:102-104 but in HBsAg-positive blood donors this particle ratio reached 1:106-1012 when viral load was below 100 HBV-DNA copies/mL. Modelled TT-HBV risk of an HBsAg-positive/ID-NAT nonreactive blood transfusion was estimated at 5.5%-27% for components containing 20-200 mL of plasma when assuming an ID50 of 316 (point estimate between 100 and 1000) virions. It cannot be ensured that discontinuation of HBsAg donor screening and reliance on ID-NAT alone is safe.

Incidences of new hepatitis B infection and anti-hepatitis B core-negative occult hepatitis B infection among Japanese blood donors in relation to anti-hepatitis B surface antigen levels

A transfusion-transmitted hepatitis B virus (HBV) infection caused by blood only positive for anti-hepatitis B surface antigen (anti-HBs) was reported. Occult HBV infection (OBI) with sole anti-HBs among blood donors is an issue. The incidence of HBV infection among repeat blood donors was investigated with a detailed HBV infection phase, focusing on the influence of anti-HBs level. This study followed 3 435 653 donors for HBV DNA conversion over 4 years and 9 months. Infection phase was determined based on marker changes over DNA conversion. This study identified 115 hepatitis B surface antigen (HBsAg) conversions, 72 DNA-only conversions, and 15 DNA plus anti-hepatitis B core (anti-HBc) conversions among donors all negative for HBV DNA, HBsAg, and anti-HBc. Total incidence was 2.38/100 000 person-years (PY). None of these 202 new HBV infections arose in the group with anti-HBs titer ≥ 10 mIU/mL. In total, 30 anti-HBc-negative OBIs were identified (incidence; 0.35/100 000 PY); 7 showed typical secondary anti-HBs response, and 23 showed stable anti-HBc and anti-HBs levels at DNA conversion. The HBV infection-protective ability of anti-HBs ≥ 10 mIU/mL was reinforced. In addition to new infections, the blood donor population includes anti-HBc-positive- and negative OBI with immune reactions or abortive HBV infection.

Prevalence and Residual Risk of HIV in Volunteer Blood Donors of Zhejiang Province, China, from 2018 to 2022

Background

Blood safety levels have been significantly improved since the implementation of nucleic acid amplification technology (NAT) testing for blood donors. However, there remains a residual risk of transfusion transmission infections. This study aimed to evaluate the prevalence of HIV and its residual risk transmission among volunteer blood donors of Zhejiang Province, China, for five years after NAT implementation.

Materials and Methods

All specimens and information were collected from voluntary unpaid donors at all blood services in Zhejiang Province, China, from January 2018 to December 2022. The HIV antibody or antigen and HIV RNA were detected using enzyme-linked immunosorbent assay and NAT, respectively. The HIV residual risk transmission was calculated using the incidence or window period model.

Results

A total of 3,375,678 voluntary blood donors were detected, revealing an HIV prevalence of 9.92/100000. The HIV prevalence of blood donors in 12 blood services in Zhejiang Province was 6.11, 6.98, 7.45, 8.21, 8.36, 8.94, 9.04, 9.66, 9.73, 10.22, 11.80, and 12.47 per 100000 donors, without statistically significant difference observed among the services (p > 0.05). The HIV prevalence of males (15.49/100000) was significantly higher compared to females (1.95/100000; p < 0.05). There was an insignificant difference in HIV prevalence among blood donors of all different age groups (p > 0.05), but the HIV prevalence in the 26-35 age group and 18-25 age group was significantly higher compared to the 36-45 age group (p < 0.05). The difference in HIV prevalence between first-time blood donors (13.65/100,000) and repeat blood donors (6.78/100,000) was statistically significant (p < 0.05). From 2018 to 2022, the HIV residual risk in blood transfusion transmission was 0.266/100000.

Conclusion

The prevalence of HIV among blood donors in Zhejiang Province, China, is associated with age, gender, and times of blood donation. The HIV residual risk in blood transfusion transmission remains low in the province, and increasing the rate of repeat blood donors is beneficial to improve blood safety.

Persistence and risk factors of occult hepatitis B virus infections among antiretroviral therapy-naïve people living with HIV in Botswana

Aim

This study aimed to determine the kinetics of occult hepatitis B virus infections (OBI) among people with HIV (PWH).

Methods

The study used archived plasma samples from longitudinal HIV natural history studies. We identified new OBI cases and assessed risk factors for OBI using Cox proportional hazards regression analysis.

Results

At baseline, 8 of 382 [(2.1%) (95% CI: 1.06-4.1)] samples tested positive for hepatitis B surface antigen (HBsAg+). Of the 374 HBsAg-negative samples, 76 had sufficient sample volume for HBV DNA screening. OBI positivity (OBI+) at baseline was reported in 11 of 76 [14.7 95% CI (8.3-24.1)] HBsAg-negative (HBsAg-) participants. Baseline HBsAg-negative samples with sufficient follow-up samples (n = 90) were used for analysis of newly identified OBI cases. Participants contributed 129.74 person-years to the study and were followed for a median of 1.02 years (IQR: 1.00-2.00). Cumulatively, there were 34 newly identified OBI cases from the 90 participants, at the rate of 26.2/100 person-years (95% CI: 18.7-36.7). Newly identified OBI cases were more common among men than women (61.1% vs. 31.9%) and among participants with CD4+ T-cell counts ≤450 cells/mL (p-value = 0.02). Most of the newly identified OBI cases [55.9% (19/34)] were possible reactivations as they were previously HBV core antibody positive.

Conclusion

There was a high rate of newly identified OBI among young PWH in Botswana, especially in men and in participants with lower CD4+ T-cell counts. OBI screening in PWH should be considered because of the risk of transmission, possible reactivation, and risk factors for the development of chronic liver disease, including hepatocellular carcinoma.

The high prevalence of occult hepatitis B infections among the partners of chronically infected HBV blood donors emphasizes the potential residual risk to blood safety

A small percentage of couples who regularly donated blood in China tested positive for HBsAg. Although it is well known that blood donors can acquire hepatitis B virus (HBV) infection from a chronically infected sexual partner, the prevalence of occult hepatitis B infections (OBIs) among blood donations from partners of HBV-infected chronically infected spouses and the risk to blood safety remain poorly understood. Among 212 763 blood donors, 54 pairs of couples (108 donations) were enrolled because one partner tested positive for HBsAg. Several molecular and serological examinations were conducted. The origin of HBV transmission between sexual partners was investigated further. Also evaluated was the potential risk of HBV infection with OBIs. We identified 10 (10/54, 18.6%) sexual partners of chronically infected HBV donors who were positive for HBV DNA, including five samples (9.3%) with OBIs, of which 3 (3/54, 5.6%, 1 in 70 921 donations) passed the routine blood screening tests. Seven of the 10 HBV-DNA-positive couples contracted the virus possibly through sexual or close contact. Among infected couples, immune escape mutations were observed. A high prevalence of OBIs was found among the partners of chronically infected HBV blood donors, posing a potential threat to blood safety.

Healthcare-associated hepatitis B and C transmission to patients in the EU/EEA and UK: a systematic review of reported outbreaks between 2006 and 2021

Healthcare-associated transmission was the second most common hepatitis B (HBV) and hepatitis C (HCV) transmission route according to 2006-2012 European surveillance data, but data quality and completeness issues hinder comprehensive characterisation of this important issue. We carried out a systematic review of published literature on healthcare-associated transmission of HBV or HCV in European Union (EU) and European Economic Area (EEA) countries and the United Kingdom to complement surveillance data and identify higher-risk settings. We searched the PubMed and Embase databases and grey literature over the period January 2006 to September 2021, for publications reporting transmission events after 2000 in the EU/EEA and UK related to a healthcare setting or procedure. We collected data on the country, number of patients, setting type and route of transmission. In 65 publications from 16 countries, 43 HBV and 48 HCV events were identified resulting in 442 newly infected patients. Most events were reported from Italy (7 HBV and 12 HCV), Germany (8 HBV and 5 HCV) and the United Kingdom (8 HBV and 5 HCV). The number of patients infected from a single source within an event ranged from 1 to 53. Five large outbreaks of over 20 cases were identified, including two in Poland and one each in Belgium, Hungary and Slovakia. The majority of transmission events occurred through blood transfusions or in dialysis units. However, there were a number of outbreaks in seemingly low risk settings such as CT/MRI scanning units. A failure to adequately follow infection prevention control (IPC) precautions was reported in 30% of included studies. Healthcare-associated transmission of hepatitis B and C continues to occur in a range of community and hospital settings across EU/EEA countries and often results in large outbreaks, although the true extent of the situation cannot be fully determined due to under-reporting. Strict IPC precautions should be implemented across all healthcare settings and regularly audited, and surveillance systems strengthened and standardised to allow for comprehensive and consistent reporting of nosocomial transmission of hepatitis across the EU.

Efficacy of Different Testing Scenarios in Reducing Transfusion-Transmitted Hepatitis B Virus (TT-HBV) Infection Risk

The efficacy of different screening scenarios in reducing hepatitis B virus (HBV) transmission risk as compared to the risk without screening was modeled in 9,337,110 donations from four geographical regions that had been subjected to hepatitis B surface antigen (HBsAg) and individual donation nucleic acid amplification testing (ID-NAT). We used the Weusten models for estimating infectivity risk for Red Blood Cell (RBC) transfusions in eight HBV infection stages and then evaluated multiple screening strategies based on minipool (MP) and ID-NAT options of different sensitivity for their efficacy in reducing this risk. The efficacy in reducing HBV transmission risk by screening scenarios across the regions varied between 81% (HBsAg only) and 99.2% (ID-NAT and anti-HBc). Highly sensitive ID-NAT alone achieved a slightly higher risk reduction (97.6−99.0%) than minipool of 6 donations (MP6)-NAT in combination with HBsAg and anti-HBc (96.3−98.7%). In ID-NAT screened lapsed and repeat donors, the additional risk removed by HBsAg testing was minimal (<0.1%). The modeling outcomes in this and two previous reports using this multi-regional database suggest that one could consider an ID-NAT alone testing scenario as an alternative to MP-NAT and serology-based testing algorithms and restrict serologic testing to first-time donors only.

Infectivity of hepatitis B virus (HBV) surface antigen (HBsAg) positive plasma with undetectable HBV-DNA: Can HBsAg screening be discontinued in Egyptian blood donors?

HBV infectivity data were reviewed and the 50% infectious dose (ID50 ) was reassessed in different HBsAg positive infection stages enabling modelling of transfusion-transmitted (TT)-HBV infection risk if HBsAg donor screening was replaced by individual donation nucleic acid amplification technology (ID-NAT). Quantitative HBsAg and HBV-DNA assays were performed against international standards to compare the ratio between potential infectious HBV virions and subviral HBsAg particles in Egyptian HBsAg positive blood donors as well as in Japanese chimpanzee samples of known infectivity. HBV-DNA load below the quantification limit of detection was estimated against a reference standard by replicate NAT testing (n = 25). Infectivity of chimpanzee samples collected during ramp-up and declining viremic phase were tested in a human liver chimeric mice (HLCM) model and compared with published infectivity data from different HBsAg positive infection stages. Lowest estimates of ID50 in HBsAg positive plasma were 3-6 HBV virions in chimpanzee studies. Infectivity decreased approximately 10-100-fold in the declining viremic phase using HLCM. In acute-phase samples, HBV to HBsAg particle ratios varied between 1:102 -104 but in HBsAg positive blood donors this particle ratio reached 1:106 -1012 when viral load was below 100 HBV-DNA copies/ml. Modelled TT-HBV risk of an HBsAg positive/ID-NAT nonreactive blood transfusion was estimated at 9%-46% for components containing 20-200 ml of plasma assuming an ID50 of 316 (point estimate between 100 and 1000) virions. In the Egyptian setting, discontinuation of HBsAg donor screening and reliance on ID-NAT alone seems to be unsafe.