SARS-CoV-2 nucleocapsid antigen in plasma of children hospitalized for COVID-19 or with incidental detection of SARS-CoV-2 infection.

In hospitalized children, SARS-CoV-2 infection can present as either a primary reason for admission (patients admitted for COVID-19) or an incidental finding during follow-up (patients admitted with COVID-19). We conducted a nested case-control study within a cohort of pediatric patients with confirmed SARS-CoV-2 infection, to investigate the concentration of plasma nucleocapsid antigen (N-Ag) in children admitted for COVID-19 or with COVID-19. While reverse transcriptase polymerase chain reaction Ct values in nasopharyngeal swab were similar between the two groups, children admitted for COVID-19 had a higher rate of detectable N-Ag (12/18 (60.7%) versus 6/18 (33.3%), p = 0.0455) and a higher concentration of N-Ag (medians: 19.51 g/mL vs. 1.08 pg/mL, p = 0.0105). In children hospitalized for COVID-19, the youngest had higher concentration of N-Ag (r = -0.74, p = 0.0004). We also observed a lower prevalence of detectable spike antibodies in children hospitalized for COVID-19 compared to those hospitalized for other medical reasons (3/15 [20%] vs. 13/16 [81.25%], respectively, p = < 0.0011), but similar rates of IgG nucleocapsid antibodies (5/14 [35.7%] vs. 6/17 [35.3%], respectively, p = 0.99). Our findings indicate that N-Ag is associated with COVID-19-related hospitalizations in pediatric patients, and less frequently detected in children tested positive for SARS-CoV-2 but hospitalized for another medical reason. Further studies are needed to confirm the value of N-Ag in identifying COVID-19 disease infections in which SARS-CoV-2 is the main pathogen responsible for symptoms.

Severe Acute Respiratory Syndrome Coronavirus 2 Nucleocapsid Antigen in Urine of Hospitalized Patients With Coronavirus Disease 2019.

BACKGROUND: Severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) nucleocapsid antigen (N-Ag) can be detected in the blood of patients with coronavirus disease 2019 (COVID-19). We used a highly sensitive and specific assay to explore the presence of N-Ag in urine during the course of COVID-19 and its relationship with the severity of disease. METHODS: We studied urinary and plasma N-Ag using a highly sensitive immunoassay in 82 patients with SARS-CoV-2 infection proved by polymerase chain reaction. RESULTS: In the first and second weeks of COVID-19, hospitalized patients tested positive for urinary N-Ag (81.25% and 71.79%, respectively) and plasma N-Ag (93.75% and 94.87%, respectively). High urinary N-Ag levels were associated with the absence of SARS-CoV-2 nucleocapsid antibodies, admission in intensive care units, high C-reactive protein levels, lymphopenia, eosinopenia, and high lactate dehydrogenase levels. Higher accuracy was observed for urinary N-Ag as a predictor of severe COVID-19 than for plasma N-Ag. CONCLUSIONS: Our study demonstrates that N-Ag is present in the urine of patients hospitalized in the early phase of COVID-19. As a direct marker of SARS-CoV-2, urinary N-Ag reflects the dissemination of viral compounds in the body. Urinary N-Ag may be a useful marker for disease severity in SARS-CoV-2 infections.

Antibody response after one and two jabs of the BNT162b2 vaccine in nursing home residents: The CONsort-19 study.

BACKGROUND: The humoral immune response following COVID-19 vaccination in nursing home residents is poorly known. A longitudinal study compared levels of IgG antibodies against the spike protein (S-RBD IgG) (S-RDB protein IgG) after one and two BNT162b2/Pfizer jabs in residents with and without prior COVID-19. METHODS: In 22 French nursing homes, COVID-19 was diagnosed with real-time reverse-transcriptase polymerase chain reaction (RT-PCR) for SARS-CoV-2. Blood S-RDB-protein IgG and nucleocapsid (N) IgG protein (N-protein IgG) were measured 21-24 days after the first jab (1,004 residents) and 6 weeks after the second (820 residents). RESULTS: In 735 residents without prior COVID-19, 41.7% remained seronegative for S-RDB-protein IgG after the first jab vs. 2.1% of the 270 RT-PCR-positive residents (p < 0.001). After the second jab, 3% of the 586 residents without prior COVID-19 remained seronegative. However, 26.5% had low S-RDB-protein IgG levels (50-1050 UA/ml) vs. 6.4% of the 222 residents with prior COVID-19. Residents with an older infection (first wave), or with N-protein IgG at the time of vaccination, had the highest S-RDB-protein IgG levels. Residents with a prior COVID-19 infection had higher S-RDB-protein IgG levels after one jab than those without after two jabs. INTERPRETATION: A single vaccine jab is sufficient to reach a high humoral immune response in residents with prior COVID-19. Most residents without prior COVID-19 are seropositive for S-RDB-protein IgG after the second jab, but around 30% have low levels. Whether residents with no or low post-vaccine S-RDB protein IgG are at higher risk of symptomatic COVID-19 requires further analysis.

Receptor binding domain-IgG levels correlate with protection in residents facing SARS-CoV-2 B.1.1.7 outbreaks.

BACKGROUND: Limited information exists on nursing home (NH) residents regarding BNT162b2 vaccine efficacy in preventing SARS-CoV-2 and severe COVID-19, and its association with post-vaccine humoral response. METHODS: 396 residents from seven NHs suffering a SARS-CoV-2 B.1.1.7 (VOC-α) outbreak at least 14 days after a vaccine campaign were repeatedly tested using SARS-CoV-2 real-time reverse-transcriptase polymerase chain reaction on nasopharyngeal swab test (RT-qPCR). SARS-CoV-2 receptor-binding domain (RBD) of the S1 subunit (RBD-IgG) was measured in all residents. Nucleocapsid antigenemia (N-Ag) was measured in RT-qPCR-positive residents and serum neutralizing antibodies in vaccinated residents from one NH. RESULTS: The incidence of positive RT-qPCR was lower in residents vaccinated by two doses (72/317; 22.7%) vs one dose (10/31; 32.3%) or non-vaccinated residents (21/48; 43.7%; p < .01). COVID-19-induced deaths were observed in 5 of the 48 non-vaccinated residents (10.4%), in 2 of the 31 who had received one dose (6.4%), and in 3 of the 317 (0.9%) who had received two doses (p = .0007). Severe symptoms were more common in infected non-vaccinated residents (10/21; 47.6%) than in infected vaccinated residents (15/72; 21.0%; p = .002). Higher levels of RBD-IgG (n = 325) were associated with a lower SARS-CoV-2 incidence. No in vitro serum neutralization activity was found for RBD-IgG levels below 1050 AU/ml. RBD-IgG levels were inversely associated with N-Ag levels, found as a risk factor of severe COVID-19. CONCLUSIONS: Two BNT162b2 doses are associated with a 48% reduction of SARS-CoV-2 incidence and a 91.3% reduction of death risk in residents from NHs facing a VOC-α outbreak. Post-vaccine RBD-IgG levels correlate with BNT162b2 protection against SARS-CoV-2 B.1.1.7.

Screening for Hepatitis B in partners and children of women positive for surface antigen, Burkina Faso.

Objective: To evaluate the implementation of a screening strategy for the partners and children of pregnant women with hepatitis B virus (HBV) attending antenatal care. Methods: We identified pregnant women positive for HBV surface antigen (HBsAg) at antenatal consultation in Ouagadougou, Burkina Faso. At post-test counselling, women were advised to disclose their HBV status to partners and to encourage their partner and children to be screened for HBsAg. We used multivariable logistic regression to explore factors associated with uptake of screening and HBsAg positivity among family members. Findings: Of 1000 HBsAg-positive women, 436/1000 partners and 215/1281 children were screened. HBsAg was detected in 55 (12.6%) partners and 24 (11.2%) children. After adjusting for confounders, uptake of screening was higher in partners who were married, who attended the woman's first post-test consultation and to whom the woman had disclosed her HBV status. In children, HBsAg positivity was associated with being born before the introduction of infant hepatitis B vaccination in Burkina Faso (not significant in the multivariable analysis), having a mother positive for HBV e-antigen (adjusted OR: 8.57; 95% CI: 2.49-29.48) or having a mother with HBV DNA level ≥ 200 000 IU/mL (OR: 6.83; 95% CI: 1.61-29.00). Conclusion: In low-income countries, the antenatal consultation provides a cost-effective opportunity to identify HBV-infected household contacts and link them to care. Children born before the introduction of infant hepatitis B vaccination and whose mother has higher viral load or infectivity should be a priority for testing and linkage to care.

Monocyte CD169 Expression as a Biomarker in the Early Diagnosis of Coronavirus Disease 2019.

We assessed the expression of CD169, a type I interferon-inducible receptor, on monocytes (monocyte CD169 [mCD169]) in 53 adult patients admitted to the hospital during the coronavirus disease 2019 (COVID-19) outbreak for a suspicion of severe acute respiratory syndrome coronavirus 2 infection. Monocyte CD169 was strongly overexpressed in 30 of 32 (93.7%) confirmed COVID-19 cases, compared with 3 of 21 (14.3%) patients in whom the diagnosis of COVID-19 was finally ruled out. Monocyte CD169 was associated with the plasma interferon-alpha level and thrombocytopenia. Monocyte CD169 testing may be helpful for the rapid triage of suspected COVID-19 patients during an outbreak.

Clinical and Biological Factors Associated With Early Epstein-Barr Virus Infection in Human Immunodeficiency Virus-Exposed Uninfected Infants in Eastern Uganda.

BACKGROUND: Immune control of Epstein-Barr virus (EBV) infection is impaired in individuals with HIV. We explored maternal factors associated with EBV acquisition in HIV-exposed uninfected (HEU) infants and the relationship between EBV infection and serious adverse events (SAEs) during the first year of life. METHODS: 201 HEU infants from Uganda enrolled in the ANRS 12174 trial were tested for antiviral capsid antigen (anti-VCA) antibodies at week 50. Date of infection was estimated by testing EBV DNA at weeks 1, 6, 14, 26, 38, and 50 postpartum on dried blood spots. RESULTS: Eighty-seven (43%) infants tested positive for anti-VCA IgG at week 50. Among the 59 infants positive for EBV DNA, 25% were infected within the first 26 weeks. Almost half (12%) were infected before week 14. Shedding of EBV in breast milk was associated with EBV DNA in maternal plasma (P = .009), HIV RNA detection (P = .039), and lower CD4 count (P = .001) and correlated with plasma EBV DNA levels (P = .002). EBV infant infection at week 50 was associated with shedding of EBV in breast milk (P = .009) and young maternal age (P = .029). Occurrence of a clinical SAE, including malaria and pneumonia, was associated with higher levels of EBV DNA in infants (P = .010). CONCLUSIONS: By assessing EBV infection in HEU infants we observed that infection during the first year is determined by HIV and EBV maternal factors and that EBV DNA levels were higher among infants with clinical SAEs. CLINICAL TRIALS REGISTRATION: NCT00640263.

Diagnosis value of SARS-CoV-2 antigen/antibody combined testing using rapid diagnostic tests at hospital admission.

The implementation of rapid diagnostic tests (RDTs) may enhance the efficiency of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) testing, as RDTs are widely accessible and easy to use. The aim of this study was to evaluate the performance of a diagnosis strategy based on a combination of antigen and immunoglobulin M (IgM) or immunoglobulin G (IgG) serological RDTs. Plasma and nasopharyngeal samples were collected between 14 March and 11 April 2020 at hospital admission from 45 patients with reverse transcription polymerase chain reaction (RT-PCR) confirmed COVID-19 and 20 negative controls. SARS-CoV-2 antigen (Ag) was assessed in nasopharyngeal swabs using the Coris Respi-Strip. For IgM/IgG detection, SureScreen Diagnostics and Szybio Biotech RDTs were used in addition to laboratory assays (Abbott Alinity i SARS-CoV-2 IgG and Theradiag COVID-19 IgM enzyme-linked immunosorbent assay). Using the Ag RDT, 13 out of 45 (29.0%) specimens tested positive, the sensitivity was 87.0% for cycle threshold (Ct ) values ≤25% and 0% for Ct values greater than 25. IgG detection was associated with high Ct values and the amount of time after the onset of symptoms. The profile of isolated IgM on RDTs was more frequently observed during the first and second week after the onset of symptoms. The combination of Ag and IgM/IgG RDTs enabled the detection of up to 84.0% of COVID-19 confirmed cases at hospital admission. Antigen and antibody-based RDTs showed suboptimal performances when used alone. However when used in combination, they are able to identify most COVID-19 patients admitted in an emergency department.

Online self-sampling kits to screen multipartner MSM for HIV and other STIs: participant characteristics and factors associated with kit use in the first 3 months of the MemoDepistages programme, France, 2018.

OBJECTIVES: In 2017, to reduce the proportion of men who have sex with men (MSM) in the undiagnosed HIV population in France (38%), HIV screening is advised each 3 months and STI screening is advised each year in multipartner MSM. Despite the range of testing solutions, over 40% of MSM were not tested for HIV and over 50% for STIs in the past year. Based on international experiments that offer screening solutions via online advertising, the French National Health Agency launched a programme (MemoDepistages) to provide a free self-sampling kit (SSK) for HIV and STIs. This article analyses the sociodemographic and behavioural characteristics of MSM in terms of kit acceptance and sample return. METHODS: Participants were registered for the programme online after ordering an SSK. The study included men aged over 18 years, living in one of the four selected French regions, and willing to disclose their postal and email address; they had health insurance, acknowledged more than one male partner in the past year, indicated a seronegative or unknown HIV status and were not taking medically prescribed pre-exposure prophylaxis drugs. Samples were collected by users and posted directly to the laboratory. Characteristics associated with kit acceptance and sample return were analysed using logistic regression. RESULTS: Overall, 7158 eligible MSM were offered to participate in the programme, with 3428 ordering the kit (47.9%) and 1948 returning their sample, leading to a return rate of 56.8% and an overall participation rate of 27.2%. Acceptance and return rates were strongly associated with sociodemographic characteristics, mainly education level but not with behavioural characteristics. Non-college graduates had lower acceptance (44.2%) and return rates (47.7%). CONCLUSION: The programme rapidly recruited a large number of MSM. It removed geographical inequalities related to screening access.

Atypical symptoms, SARS-CoV-2 test results and immunisation rates in 456 residents from eight nursing homes facing a COVID-19 outbreak.

BACKGROUND: Frail older persons may have an atypical presentation of coronavirus disease 2019 (COVID-19). The value of real-time reverse-transcriptase polymerase chain reaction (rRT-PCR) testing for identifying severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) nursing homes (NHs) residents is not known. OBJECTIVE: To determine whether (i) atypical symptoms may predict rRT-PCR results and (ii) rRT-PCR results may predict immunisation against SARS-CoV-2 in NH residents. DESIGN: A retrospective longitudinal study. SETTING: Eight NHs with at least 10 rRT-PCR-positive residents. SUBJECTS: A total of 456 residents. METHODS: Typical and atypical symptoms recorded in residents' files during the 14 days before and after rRT-PCR testing were analysed. Residents underwent blood testing for IgG-SARS-CoV-2 nucleocapsid protein 6 to 8 weeks after testing. Univariate and multivariate analyses compared symptoms and immunisation rates in rRT-PCR-positive and negative residents. RESULTS: A total of 161 residents had a positive rRT-PCR (35.3%), 17.4% of whom were asymptomatic before testing. Temperature >37.8°C, oxygen saturation <90%, unexplained anorexia, behavioural change, exhaustion, malaise and falls before testing were independent predictors of a further positive rRT-PCR. Among the rRT-PCR-positive residents, 95.2% developed SARS-CoV-2 antibodies vs 7.6% in the rRT-PCR-negative residents. Among the residents with a negative rRT-PCR, those who developed SARS-CoV-2 antibodies more often had typical or atypical symptoms (P = 0.02 and <0.01, respectively). CONCLUSION: This study supports a strategy based on (i) testing residents with typical or unexplained atypical symptoms for an early identification of the first SARS-CoV-2 cases, (ii) rT-PCR testing for identifying COVID-19 residents, (iii) repeated wide-facility testing (including asymptomatic cases) as soon as a resident is tested positive for SARS-CoV-2 and (iv) implementing SARS-CoV-2 infection control measures in rRT-PCR-negative residents when they have unexplained typical or atypical symptoms.

Hepatitis B and C virus seroprevalence, Burkina Faso: a cross-sectional study.

OBJECTIVE: To estimate population-wide hepatitis B and C seroprevalence using dried blood spot samples acquired for human immunodeficiency virus (HIV) surveillance as part of the 2010-2011 Demographic and Health Survey in Burkina Faso. METHODS: We used the database acquired during the multistage, clustered, population-based survey, in which 15 377 participants completed questionnaires and provided dried blood spot samples for HIV testing. We extracted sociodemographic and geographic data including age, sex, ethnicity, education, wealth, marital status and region for each participant. We performed hepatitis B and C assays on 14 886 HIV-negative samples between March to October 2015, and calculated weighted percentages of hepatitis seroprevalence for each variable. FINDINGS: We estimated seroprevalence as 9.1% (95% confidence interval, CI: 8.5-9.7) for the hepatitis B surface antigen and 3.6% (95% CI: 3.3-3.8) for hepatitis C virus antibodies, classifying Burkina Faso as highly endemic for hepatitis B and low-intermediate for hepatitis C. The seroprevalence of hepatitis was higher in men than in women, and varied significantly for both with age, education, ethnicity and region. Extremely high HCV-Ab seroprevalence (13.2%; 95% CI: 10.6-15.7) was identified in the Sud-Ouest region, in particular within the youngest age group (15-20 years), indicating an ongoing epidemic. CONCLUSION: Our population-representative hepatitis seroprevalence estimates in Burkina Faso advocate for the inclusion of hepatitis serological tests and risk factor questionnaire items in future surveys, the results of which are crucial for the development of appropriate health policies and infection control programmes.

Leptospirosis Cases among Outpatients with Non-Malaria Fever Attending Primary Care Clinics during the Rainy Season in Bobo Dioulasso, Burkina Faso.

Leptospirosis is presumably an important cause of non-malarial fever in West Africa. In this study, outpatients consulting in primary care clinics during the rainy season were tested for leptospirosis, and clinical characteristics associated with leptospirosis cases were explored. Patients with fever ≥ 39°C were recruited in nine primary health care centers in Bobo Dioulasso (Burkina Faso). Diagnosis of malaria was ruled out using a rapid diagnostic test (RDT; SD Bioline Malaria®). Leptospirosis cases were defined as patients who tested positive for Leptospira IgM (Leptocheck-WB RDT and Leptospira IgM ELISA assay, Panbio) or DNA in plasma (LipL32 polymerase chain reaction [PCR]). Among 350 patients, 202 tested positive for malaria and were excluded, and 148 met the eligibility criteria and were included. Among these, 26 subjects were considered to be leptospirosis cases: 23 tested positive for Leptospira IgM (15.5%) and three tested positive by PCR (2.2%). Headaches, abdominal symptoms, and myalgia were frequently reported without any difference between leptospirosis cases and negative cases. Cough was more frequently observed among subjects testing positive for leptospirosis (P = 0.02). Water exposure, presence of a skin injury, and walking barefoot were associated with a Leptospira-positive test. All leptospirosis cases recovered without sequelae. A significant portion of outpatients with non-malarial febrile illness during the rainy season in Burkina Faso had epidemiological factors associated with leptospirosis and tested positive for Leptospira. The favorable outcome of leptospirosis cases was reassuring; this could be due in particular to the young age of the patients.

Combination of serological and cytokine release assays for improved diagnosis of childhood tuberculosis in Zambia (PROMISE-TB).

OBJECTIVES: The diagnostic gaps for childhood tuberculosis (TB) remain considerable in settings with high TB incidence and resource constraints. We established and evaluated the performance of a scoring system based on a combination of serological tests and T-cell cytokine release assays, chosen for their ability to detect immune responses indicative of TB, in a context of high prevalence of pediatric HIV infection. METHODS: We enrolled 628 consecutive children aged ≤15 years, admitted for TB suspicion. Multiple cytokine levels in QuantiFERON Gold In-Tube supernatants and antigen 85B (Ag85B) antibodies were assessed in children who tested positive with either Xpert TB or mycobacterial culture. The results were compared with those of control children. RESULTS: Among the biomarkers most strongly associated with TB, random forest classification analysis selected Ag85B antibodies, interleukin-2/interferon-γ ratio, and monokine induced by interferon-γ for the scoring system. The receiver operating characteristic curve derived from our scoring system showed an area under the curve of 0.95 (0.91-0.99), yielding 91% sensitivity and 88% specificity. The internal bootstrap validation gave the following 95% confidence intervals for the score performance: sensitivity 71%-97% and specificity 79%-99%. CONCLUSIONS: This study suggests that supplementing the QuantiFERON assay with a combination of serological and T-cell markers could enhance childhood TB screening regardless of HIV status and age. Further validation among the target population is necessary to confirm the performance of this scoring system.

Development and field evaluation in African and Asian countries of an hepatitis B virus PCR on open polyvalent platforms to determine treatment eligibility: results from the "Agence Nationale de Recherche sur le Sida et les hépatites" 12327 study.

OBJECTIVES: Widespread testing and treatment are essential to eliminate hepatitis B virus (HBV) infection as a public health concern. However, in resource-limited countries, access to HBV PCR is limited. In this study, we developed a quantitative HBV PCR assay on open molecular platforms and evaluate its performance in diagnosing clinically significant HBV DNA thresholds as defined by the WHO (2000 IU/mL, 20 000 IU/mL, and 200 000 IU/mL). METHODS: We implemented our HBV PCR test in seven African and Asian countries and France, using either an in-house laboratory method or a European conformity for in vitro diagnostic (CE-IVD) marked version of the PCR (Generic HBV Charge Virale, Biocentric). Results were compared with reference tests (Roche Cobas AmpliPrep/Cobas TaqMan and Abbott RealTime on Abbott m2000). RESULTS: There was a good agreement between the HBV DNA results of 1015 samples tested by the PCR on open polyvalent platforms and the results from reference tests (mean difference (bias ± standard deviation [SD]): -0.3 ± 0.7 log10 IU/mL and -0.2 ± 0.9 log10 IU/mL when compared with Roche and Abbott tests, respectively). Kappa-Cohen agreements between the HBV PCR on open polyvalent platforms and the Roche/Abbott assays appeared almost perfect for HBV DNA levels ranged from >20 000 to 200 000 IU/mL and >200 000 IU/mL, substantial and moderate for HBV DNA levels ranged from 2000 to 20 000 IU/mL when compared with Abbott and Roche, respectively. The assay's performance was consistent across genotypes A, B, C, D, and E. DISCUSSION: This field evaluation showed that our HBV PCR test is a valuable alternative to proprietary PCR systems. PCR assays on open platforms contribute to expanding clinical laboratory solutions for diagnosing individuals who meet the viral load criteria for antiviral therapy (>20 000 IU/mL) and mother-to-child prophylaxis (>200 000 IU/mL).

Automated and combined HIV, HBV, HCV, and syphilis testing among illegal gold miners in French Guiana using a standardized dried blood device.

Blood spotted onto filter paper can be easily collected outside healthcare facilities and shipped to a central laboratory for serological testing. However, dried blood testing generally requires manual processing for pre-analytical steps. In this study, we used a standardized blood collection device combined with an automated elution system to test illegal gold miners living in French Guiana for human immunodeficiency virus (HIV), hepatitis B virus (HBV), hepatitis C virus (HCV) and syphilis. We included 378 participants, 102 females and 266 males, in three illegal gold mining resting sites. Blood collected on the Ser-Col device (Labonovum) was eluted using an automated system (SCAUT Ser-Col automation, Blok System Supply) and an automated analyzer (Alinity i, Abbott). Ser-Col results were compared to both plasma results, considered the gold standard, and to Dried blood Spot (DBS) results, considered the reference sampling method using dried blood. In plasma samples, two participants (0.5%) tested positive for HIV, six (1.5%) tested positive for hepatitis B surface antigen (HBsAg), eight were weakly positive for anti-HCV antibodies but negative for HCV RNA, and 47 tested positive for treponemal antibodies (12.4%), including 20 females (19.6%) and 27 males (9.8%, p= 0.010179). We observed a full concordance of Ser-Col and DBS results for HIV diagnosis compared to plasma results. Ser-Col and DBS samples tested positive in five HBsAg carriers and negative for one participant with a low HBsAg level in plasma (0.5 IU/mL). All participants tested negative for HCV in Ser-Col and DBS samples, including the eight participants who tested low positive for HCV antibodies and HCV RNA negative in plasma. Among syphilis seropositive participants, 41 (87.2%) and 40 (85.1%) tested positive for treponemal antibodies in Ser-Col and DBS samples, respectively. The Ser-Col method allows automated dried blood testing of HIV, HBV, HCV and syphilis with performances comparable to DBS. Automated approaches to test capillary blood transported on dried blood devices may facilitate large-scale surveys and improve testing of populations living in remote areas.

Strong Decay of SARS-CoV-2 Spike Antibodies after 2 BNT162b2 Vaccine Doses and High Antibody Response to a Third Dose in Nursing Home Residents.

OBJECTIVES: To measure the antibody decay after 2 BNT162b2 doses and the antibody response after a third vaccine dose administered 6 months after the second one in nursing home residents with and without prior COVID-19. DESIGN: Cohort study. SETTING AND PARTICIPANTS: Four hundred-eighteen residents from 18 nursing homes. METHODS: Blood receptor-binding domain (RBD)-IgG (IgG II Quant assay, Abbott Diagnostics; upper limit: 5680 BAU) and nucleocapsid-IgG (Abbott Alinity) were measured 21‒28 days after the second BNT162b2 dose, as well as 1‒3 days before and 21‒28 days after the third vaccine dose. RBD-IgG levels of ≥592 BAU/mL were considered as high antibody response. Residents with prior positive quantitative reverse transcription polymerase chain reaction on a nasopharyngeal swab or with N-IgG levels above 0.8 S/CO were considered as prior COVID-19 residents. RESULTS: In prior COVID-19 residents (n = 122), RBD-IgG median levels decreased by 82% in 167 days on average. In the same period, the number of residents with a high antibody response decreased from 88.5% to 54.9% (P < .0001) and increased to 97.5% after the third vaccine dose (P = .02 vs the first measure). In residents without prior COVID-19 (n = 296), RBD-IgG median levels decreased by 89% in 171 days on average. The number of residents with a high antibody response decreased from 29.4% to 1.7% (P < .0001) and increased to 88.4% after the third vaccine dose (P < .0001 vs the first measure). CONCLUSIONS AND IMPLICATIONS: The strong and rapid decay of RBD-IgG levels after the second BNT162b2 dose in all residents and the high antibody response after the third dose validate the recommendation of a third vaccine dose in residents less than 6 months after the second dose, prioritizing residents without prior COVID-19. The slope of RBD-IgG decay after the third BNT162b2 dose and the protection level against SARS-CoV-2 B.1.1.529 (omicron) and other variants of concern provided by the high post-boost vaccination RBD-IgG response require further investigation in residents.

Analysing different exposures identifies that wearing masks and establishing COVID-19 areas reduce secondary-attack risk in aged-care facilities.

BACKGROUND: The COVID-19 epidemic has spread rapidly within aged-care facilities (ACFs), where the infection-fatality ratio is high. It is therefore urgent to evaluate the efficiency of infection prevention and control (IPC) measures in reducing SARS-CoV-2 transmission. METHODS: We analysed the COVID-19 outbreaks that took place between March and May 2020 in 12 ACFs using reverse transcription-polymerase chain reaction (RT-PCR) and serological tests for SARS-CoV-2 infection. Using maximum-likelihood approaches and generalized linear mixed models, we analysed the proportion of infected residents in ACFs and identified covariates associated with the proportion of infected residents. RESULTS: The secondary-attack risk was estimated at 4.1%, suggesting a high efficiency of the IPC measures implemented in the region. Mask wearing and the establishment of COVID-19 zones for infected residents were the two main covariates associated with lower secondary-attack risks. CONCLUSIONS: Wearing masks and isolating potentially infected residents appear to be associated with a more limited spread of SARS-CoV-2 in ACFs.