Population-Weighted Seroprevalence From Severe Acute Respiratory Syndrome Coronavirus 2 (SARS-CoV-2) Infection, Vaccination, and Hybrid Immunity Among US Blood Donations From January to December 2021

BACKGROUND

Previous severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) infection and coronavirus disease 2019 (COVID-19) vaccination, independently and combined ("hybrid immunity"), result in partial protection from subsequent infection and strong protection from severe disease. Proportions of the US population who have been infected, vaccinated, or have hybrid immunity remain unclear, posing a challenge for assessing effective pandemic mitigation strategies.

METHODS

In this serial cross-sectional study, nationwide blood donor specimens collected during January-December 2021 were tested for anti-spike and anti-nucleocapsid antibodies, and donor COVID-19 vaccination history of ≥1 dose was collected. Monthly seroprevalence induced from SARS-CoV-2 infection, COVID-19 vaccination, or both, were estimated. Estimates were weighted to account for demographic differences from the general population and were compared temporally and by demographic factors.

RESULTS

Overall, 1 123 855 blood samples were assayed. From January to December 2021, the weighted percentage of donations with seropositivity changed as follows: seropositivity due to vaccination without previous infection, increase from 3.5% (95% confidence interval, 3.4%-3.7%) to 64.0%, (63.5%-64.5%); seropositivity due to previous infection without vaccination, decrease from 15.6% (15.2%-16.0%) to 11.7% (11.4%-12.0%); and seropositivity due to hybrid immunity, increase from 0.7% (0.6%-0.7%) to 18.9% (18.5%-19.3%). Combined seroprevalence from infection, vaccination, or both increased from 19.8% (19.3%-20.2%) to 94.5% (93.5%-94.0%). Infection- and vaccination-induced antibody responses varied significantly by age, race-ethnicity, and region, but not by sex.

CONCLUSIONS

Our results indicate substantial increases in population humoral immunity from SARS-CoV-2 infection, COVID-19 vaccination, and hybrid immunity during 2021. These findings are important to consider in future COVID-19 studies and long-term pandemic mitigation efforts.

How do we…form and coordinate a national serosurvey of SARS-CoV-2 within the blood collection industry?

Background

A national serosurvey of U.S. blood donors conducted in partnership with the Centers for Disease Control and Prevention (CDC) was initiated to estimate the prevalence of SARS‐CoV‐2 infections and vaccinations.

Methods

Beginning in July 2020, the Nationwide Blood Donor Seroprevalence Study collaborated with multiple blood collection organizations, testing labs, and leadership from government partners to capture, test, and analyze approximately 150,000 blood donation specimens per month in a repeated, cross‐sectional seroprevalence survey.

Results

A CDC website (https://covid.cdc.gov/covid-data-tracker/#nationwide-blood-donor-seroprevalence) provided stratified, population‐level results to public health professionals and the general public.

Discussion

The study adapted operations as the pandemic evolved, changing specimen flow and testing algorithms, and collecting additional data elements in response to changing policies on universal blood donation screening and administration of SARS‐CoV‐2 spike‐based vaccines. The national serosurvey demonstrated the utility of serosurveillance testing of residual blood donations and highlighted the role of the blood collection industry in public–private partnerships during a public health emergency.

Serologic screening of United States blood donors for Babesia microti using an investigational enzyme immunoassay

BACKGROUND

The tick-borne pathogen Babesia microti has become recognized as the leading infectious risk associated with blood transfusion in the United States, yet no Food and Drug Administration-licensed screening tests are currently available to mitigate this risk. The aim of this study was to evaluate the performance of an investigational enzyme immunoassay (EIA) for B. microti as a screening test applied to endemic and nonendemic blood donor populations.

STUDY DESIGN AND METHODS

The study aimed to test 20,000 blood donors from areas of the United States considered endemic for B. microti and 10,000 donors from a nonendemic area with the investigational B. microti EIA. Repeat-reactive samples were retested by polymerase chain reaction (PCR), blood smear, immunofluorescent assay (IFA), and immunoblot assay. In parallel, serum samples from symptomatic patients with confirmed babesiosis were tested by EIA, IFA, and immunoblot assays.

RESULTS

A total of 38 of 13,757 (0.28%) of the donors from New York, 7 of 4583 (0.15%) from Minnesota, and 11 of 8363 (0.13%) from New Mexico were found repeat reactive by EIA. Nine of the 56 EIA repeat-reactive donors (eight from New York and one from Minnesota) were positive by PCR. The specificity of the assay in a nonendemic population was 99.93%. Among IFA-positive clinical babesiosis patients, the sensitivity of the assay was 91.1%.

CONCLUSION

The B. microti EIA detected PCR-positive, potentially infectious blood donors in an endemic population and exhibited high specificity among uninfected and unexposed individuals. The EIA promises to provide an effective tool for blood donor screening for B. microti in a format amenable to high-throughput and cost-effective screening.

A prospective evaluation of chronic Babesia microti infection in seroreactive blood donors

BACKGROUND

Babesia microti is the foremost infectious risk to the US blood supply for which a Food and Drug Administration (FDA)-licensed test is unavailable for donation screening. Characterization of the antibody response to B. microti and correlation with parasitemia is necessary to guide screening and donor management policies.

STUDY DESIGN AND METHODS

During an FDA licensure trial, blood donors were prospectively screened (July-November 2013) using a B. microti-specific antibody enzyme immunoassay (EIA, Immunetics) in highly endemic (New York [NY]; n = 13,688), moderately endemic (Minnesota [MN]; n = 4583), and nonendemic (New Mexico [NM]; n = 8451) regions. Blood donors with repeat-reactive (RR) results participated in a 12-month prospective cohort study using B. microti EIA, immunofluorescent assay, polymerase chain reaction (PCR), blood smear, and clinical questionnaire.

RESULTS

Thirty-seven (61.67%; 24 NY, seven MN, six NM) of 60 eligible RR donors enrolled in the study; 20 of 37 (54%) completed the 12-month follow-up visit of which 15 (75%) were still seroreactive. Nine PCR-positive donors were identified during index screening; five participated in the follow-up study, three were PCR positive at 6 months, and two remained positive at final follow-up (378 and 404 days). Most RR donors displayed low-level seroreactivity that was either stable or waning during follow-up. The level and pattern of reactivity correlated poorly with PCR positivity.

CONCLUSION

The findings indicate prolonged seropositivity in blood donors. Although rare, asymptomatic, persistent PCR positivity supports the current policy of indefinite deferral for donors with a history of babesiosis or positive test results. Repeat testing by PCR and serology will be necessary if reinstatement is to be considered.

Determination of Babesia microti seroprevalence in blood donor populations using an investigational enzyme immunoassay

BACKGROUND

Transfusion-transmitted babesiosis caused by Babesia microti has emerged as a significant risk to the US blood supply. This study estimated the prevalence of B. microti antibodies in blood donors using an investigational enzyme immunoassay (EIA).

STUDY DESIGN AND METHODS

A peptide-based EIA that detects both immunoglobulin (Ig)G and IgM antibodies to B. microti was developed and validated. Donor samples randomly selected from areas defined as high-risk endemic, lower-risk endemic, and nonendemic for B. microti were deidentified and tested using the investigational EIA. Samples that were EIA repeat reactive were further tested by B. microti immunofluorescent assay (IFA), polymerase chain reaction (PCR) on red blood cell lysates, and peripheral blood smear examination. A random subset of 1272 samples from high-risk endemic areas was tested by IFA, PCR, and peripheral blood smear in parallel with EIA.

RESULTS

Among 15,000 donations tested with the investigational B. microti EIA, EIA repeat-reactive rates were 1.08% (54/5000) in a high-risk endemic area, 0.74% (37/5000) in a lower-risk area, and 0.40% (20/5000) in a nonendemic area. After application of a revised cutoff, these values were reduced to 0.92%, (46/5000), 0.54% (27/5000), and 0.16% (8/5000). Overall concordance between EIA and IFA among donor samples was 99.34%. One seropositive sample was positive by PCR.

CONCLUSION

The seroprevalence of B. microti in blood donors in a high-risk area measured by an investigational EIA was approximately 1%. The EIA shows promise as an efficient high-throughput blood donor screening assay for B. microti.

Comparison of Hepatitis C Virus RNA and antibody detection in dried blood spots and plasma specimens

BACKGROUND

Current diagnostic tests for Hepatitis C Virus (HCV) involve phlebotomy and serologic testing for HCV antibodies (anti-HCV) and RNA, which are not always feasible. Dried blood spots (DBS) present a minimally invasive sampling method and are suitable for sample collection, storage and testing.

OBJECTIVES

To assess the utility of DBS in HCV detection, we evaluated the sensitivity and specificity of DBS for anti-HCV and HCV RNA detection compared to plasma specimens.

STUDY DESIGN

This cross-sectional validation study was conducted in the context of an existing prospective study of HCV in young injection drug users. Blood samples were collected by venipuncture into serum separator tubes (SST) and via finger stick onto Whatman 903(®) protein-saver cards. Plasma samples and eluates from the DBS were tested for anti-HCV using either a third generation enzyme-linked or chemiluminescent immunoassay (IA), and HCV RNA using discriminatory HCV transcription-mediated amplification assay (dHCV TMA). DBS results were compared to their corresponding plasma sample results.

RESULTS

148 participants were tested for anti-HCV and 132 participants were tested for HCV RNA. For anti-HCV, the sensitivity of DBS was 70%, specificity was 100%, positive predictive value (PPV) was 100%, negative predictive value (NPV) was 76% and Kappa was 0.69. For HCV RNA, the sensitivity of DBS was 90%, specificity was 100%, PPV was 100%, NPV was 94% and Kappa was 0.92.

CONCLUSIONS

DBS are sensitive and very specific in detecting anti-HCV and HCV RNA, demonstrate good correlation with plasma results, and have potential to facilitate diagnosis of HCV infection.

Human T-lymphotropic virus laboratory testing of maternal blood at time of cord blood donations and clinical implications

BACKGROUND

In the United States, blood products are tested for infectious diseases including human T-lymphotropic virus (HTLV)-I/II. Positive results of maternal blood samples at the time of cord blood (CB) donation must be reported to mother and physician. Tests for HTLV have a high false-positive rate. This is problematic because there is no prenatal testing of the mother.

STUDY DESIGN AND METHODS

This study involves 119,769 maternal blood samples at time of CB donation and evaluates positive results for HTLV in screening tests, supplemental immunoassays, and nucleic acid tests (NATs). Infectious disease markers (IDMs) and maternal health histories of HTLV-positive and -negative mothers were compared.

RESULTS

Of 119,769 mothers donating CB, 545 tested positive with the screening test, 33 were positive with the supplemental tests, and two were positive with NAT. When indeterminate results were excluded from the supplemental test only six were positive. Eight of 34 mothers with positive or indeterminate supplemental test results had received intravenous immunoglobulin. There were no significant differences between HTLV-positive and -negative mothers with regard to the incidence of other IDMs.

CONCLUSIONS

Testing maternal blood for HTLV is problematic for CB banks, obstetricians, and mothers because of the high false-positive rate. CB banks need rapid turnaround time and supplemental testing. If results on the latter are positive the obstetrician should be notified, educated, do follow-up testing, and counseling. Indeterminate results on supplemental tests are most likely false positives. We recommend that mothers with positive or indeterminate supplemental test results have follow-up NAT.

Increased all-cause, liver, and cardiac mortality among hepatitis C virus-seropositive blood donors

Hospital-based studies suggest that hepatitis C virus (HCV) infection causes frequent cirrhosis, hepatocellular carcinoma, and mortality, but epidemiologic studies have shown less morbidity and mortality. The authors performed a retrospective cohort study of 10,259 recombinant immunoblot assay-confirmed, HCV antibody-positive (HCV+), allogeneic blood donors from 1991 to 2002 and 10,259 HCV antibody-negative (HCV-) donors matched for year of donation, age, gender, and Zone Improvement Plan Code (ZIP Code). Vital status through 2003 was obtained from the US National Death Index, and hazard ratios with 95% confidence intervals were calculated by survival analysis. After a mean follow-up of 7.7 years, there were 601 (2.92%) deaths: 453 HCV+ and 148 HCV- (hazard ratio (HR) = 3.13, 95% confidence interval (CI): 2.60, 3.76). Excess mortality in the HCV+ group was greatest in liver-related (HR = 45.99, 95% CI: 11.32, 186.74), drug- or alcohol-related (HR = 10.81, 95% CI: 4.68, 24.96), and trauma/suicide (HR = 2.99, 95% CI: 2.05, 4.36) causes. There was also an unexpected increase in cardiovascular mortality among the HCV+ donors (HR = 2.21, 95% CI: 1.41, 3.46). HCV infection is associated with a significant, threefold increase in overall mortality among former blood donors, including significantly increased mortality from liver and cardiovascular causes. High rates of mortality from drug/alcohol and trauma/suicide causes are likely due to lifestyle factors and may be at least partially preventable.

Evaluation of a rapid method for measurement of catalase activity in cooked beef and sausage

Catalase (CAT) activity in ground beef and pork was determined on samples cooked from 60 to 71.1 degrees C. One-gram samples of ground round (4% fat), hamburger (24% fat), and commercial pork sausage (38%fat) were cooked in a controlled-temperature waterbath at 65, 68.3 and 71 degrees C. Chilled samples were immersed in direct contact with the cooking water; the test samples were removed every 15 s and immediately immersed in an ice-water bath (O to 1 degrees C) to quick-chill the samples to prevent temperature over-run. Samples retained high (HMB value 20+, over range) CAT activity through 90, 60, and 45 s at 65, 68.3, and 71 degrees C, respectively, before showing rapid activity decreases. Four USDA-FSIS approved meat patty heating processes (66.1 degrees C, 41 s; 67.2 degrees C, 26 s; 68.3 degrees C, 16 s; and 69.4 degrees C, 10 s) were analyzed for CAT activity in meat frozen prior to cooking was slightly lower (P < 0.05) than in degrees C meat. CAT activity decreased (P < 0.05) among meat treated at 66.1 degrees C for 41 s, at 67.2 degrees C for 26 s, and at 68.3 degrees C for 16 s, but the treatment at 68.3 degrees C for 16 s was not different (P < 0.05) from that at 69.4 degrees C for 10 s. These results show this rapid (20 to 25 min) CAT activity test could be used to establish activity values at specific end-point temperatures for model heat-processed ground beef or sausage products and may be useful to USDA FSIS process inspectors and food processors in quality assurance and HACCP (hazard analysis critical control points) programs for thermal input verification.

Human T-cell leukemia virus type II infection frequently goes undetected in contemporary US blood donors

Serologic screening for human T-cell leukemia virus type I (HTLV-I) infection was begun in US blood banks with the licensure of enzyme-linked immunosorbent assays (ELISA) in December 1988. We examined the donation histories of the first 60 Western blot (WB)-confirmed HTLV-I/II positive donors to one blood center and found 8 had made 16 previous donations that scored negative on the screening ELISA. All 16 donations had ELISA absorbance below the cutoff for a positive assay, but still well above that of the average donation (17.6% +/- 5.7% of the cutoff). In a more extensive study, 17 donations from a total of 61,752 at six blood centers were both ELISA-positive and WB-positive for HTLV-I (4) or HTLV-II (13), and 218 samples had ELISA absorbance greater than 50% of the ELISA cutoff. One hundred seventy-eight of the 218 were tested further by WB and 11 were found positive. All 11 positives were confirmed by polymerase chain reaction; 10 had HTLV-II and 1 had HTLV-I. Thus, the HTLV-I-based screening ELISA missed at least 10 of 23, or 43% (95% confidence interval, 23% to 66%), of HTLV-II infections, compared with 1 of 5, or 20%, of HTLV-I infections.

Primary isolation of human T-cell leukemia-lymphoma virus types I and II: use for confirming infection in seroindeterminate blood donors

We describe the use of an immunofluorescence assay and coculture to confirm human T-cell leukemia-lymphoma virus (HTLV) infection. Peripheral blood mononuclear cells from 32 of 32 seropositive donors were positive in the immunofluorescence assay, and 63% of their cocultures produced p24 antigen. Specific antibodies distinguished HTLV type I (HTLV-I) from HTLV-II. HTLV-I or HTLV-II was isolated from donors with indeterminate serologic test results.

Serologic distinction between human T-lymphotropic virus (HTLV) type I and HTLV type II

In November 1988, the Food and Drug Administration approved reagents for serologic screening for human T-lymphotropic virus type I (HTLV-I) infection in blood donors and patients suspected of having HTLV-I-related illnesses. These reagents are able to detect HTLV type II (HTLV-II), a close relative of HTLV-I with no known pathologic effect. The distinction between the two forms of HTLV is important to the donor and to any recipient of blood containing HTLV. The application to sera from 38 seropositive blood donors and 2 recipients (37 "confirmed" positive and 3 indeterminate by Western blot) of two methods (Western blot and peptide enzyme immunoassay) for serologic distinction between HTLV-I and -II is described. These results were compared to those from polymerase chain reaction (PCR) analysis of HTLV proviral DNA obtained from donor peripheral blood mononuclear cells. The peptide enzyme immunoassay was found to be less sensitive than the Western blot, but completely concordant with PCR results when differential reactivity could be established. The Western blot pattern showed complete diagnostic concordance with the samples with confirmed-positive serologic tests, but was incorrect in two HTLV-II-infected donors with indeterminate serologic tests. Thirty-three (89%) of the 37 individuals from this predominantly Native American and Hispanic group of blood donors were found to have HTLV-II. These findings confirm and extend previous reports that HTLV-I infection may be less common, and HTLV-II infection more common, than previously believed. The peptide enzyme immunoassay can provide most individuals who have positive results with the HTLV-I/II screening test with serologic distinction between HTLV-I and HTLV-II.