Safety and immunogenicity of a delayed booster dose of the rVSVΔG-ZEBOV-GP vaccine for prevention of Ebola virus disease: a multicentre, open-label, phase 2 randomised controlled trial.

BACKGROUND: rVSVΔG-ZEBOV-GP is the first approved vaccine with clinical efficacy against Ebola virus disease. Although a seroprotective threshold has not been defined for those at occupational risk of exposure, the current vaccine strategy is to attain a sustained high level of antibody titres. The aim of this trial was to explore the effects of delayed boosting upon both the height and duration of antibody titres following primary immunisation. METHODS: In this open-label phase 2 randomised controlled trial, we compared antibody titres at month 36 in participants who had received a homologous booster dose at month 18 following primary immunisation with those who had received no booster. From Oct 25, 2016, to Jan 29, 2020, healthy adults aged 18 years or older deemed at occupational risk of exposure to Ebola virus due to laboratory work, clinical duties, or travel to an active endemic region were recruited from four hospital clinics in the USA and one hospital clinic in Canada and received primary vaccination with 2×107 plaque-forming unit per mL of VSVΔG-ZEBOV-GP. 18 months later, individuals who consented and were still eligible were randomly assigned 1:1 to receive either a homologous booster dose or no booster. Study visits for safety and serial blood collections for antibody titres were done on enrolled participants at months 0, 1, 3, 6, 12, 18, 19, 24, 30, and 36. Through July, 2021, a web-based application was used for randomisation, including assignments with schedules for each of the five sites using mixed permuted blocks. The trial was not masked to participants or site staff. The primary endpoint was a comparison of geometric mean titres (GMTs) of anti-Ebola virus glycoprotein IgG antibody at month 36 (ie, 18 months after randomisation) for all randomly assigned participants who completed the 36 months of follow-up (primary analysis cohort). Investigators were aware of antibody titres from baseline (enrolment) through month 18 but were masked to summary data by randomisation group after month 18. This study is registered with ClinicalTrials.gov (NCT02788227). FINDINGS: Of the 248 participants who enrolled and received their primary immunisation, 114 proceeded to the randomisation step at month 18. The two randomisation groups were balanced: 57 participants (24 [42%] of whom were female; median age was 42 years [IQR 35-50]) were randomly assigned to the booster group and 57 (24 [42%] of whom were female; median age was 42 years [IQR 36-51]) to the no-booster group. Of those randomly assigned, 92 participants (45 in the booster group and 47 in the no-booster group) completed 36 months of follow-up. At 18 months after primary immunisation, GMTs in the no-booster group increased from a baseline of 10 ELISA units (EU)/mL (95% CI 7-14) to 1451 EU/mL (1118-1882); GMTs in the booster group increased from 9 EU/mL (6-16) to 1769 EU/mL (1348-2321). At month 19, GMTs were 31 408 EU/mL (23 181-42 554) for the booster group and 1406 EU/mL (1078-1833) for the no-booster group; at month 36, GMTs were 10 146 EU/mL (7960-12 933) for the booster group and 1240 EU/mL (984-1563) for the no-booster group. Accordingly, the geometric mean ratio (GMR) of antibody titres had increased almost 21-fold more in the booster versus no-booster group at 1 month after booster administration (GMR 20·6; 95% CI 18·2-23·0; p<0·0001) and was still over 7-fold higher at month 36 (GMR 7·8; 95% CI 5·5-10·2; p<0·0001). Consistent with previous reports of this vaccine's side-effects, transient mono-articular or oligo-articular arthritis was diagnosed in 18 (9%) of 207 primary vaccination recipients; after randomisation, arthritis was diagnosed in one (2%) of 57 participants in the no-booster group. No new cases of arthritis developed after booster administration. Four serious adverse events occurred following randomisation: one (epistaxis) in the booster group and three (gastrointestinal haemorrhage, prostate cancer, and tachyarrhythmia) in the no-booster group. None of the serious adverse events was judged attributable to the booster vaccination assignment. INTERPRETATION: In addition to no new safety concerns and in marked contrast to earlier trials evaluating short-term boosting, delaying a rVSVΔG-ZEBOV-GP booster until month 18 resulted in an increase in GMT that remained several-fold above the no-booster group GMT for at least 18 months. These findings could have implications for defining the optimal timing of booster doses as pre-exposure prophylaxis in populations at ongoing risk for Ebola virus exposure. FUNDING: The Division of Intramural Research and the Division of Clinical Research of the National Institute of Allergy and Infectious Diseases at the US National Institutes of Health, Canadian Immunization Research Network through the Public Health Agency of Canada, Canadian Institutes of Health Research, and the US Defense Threat Reduction Agency.

Pregnancy, pregnancy outcomes, and infant growth and development after recovery from Ebola virus disease in Liberia: an observational cohort study.

BACKGROUND: Minimal data exist on pregnancy following recovery from Ebola in people of child-bearing potential (females aged roughly 18-45 years). The aim of this study was to assess viral persistence or reactivation in pregnancy, the frequency of placental transfer of anti-Ebola IgG antibodies, and pregnancy outcomes in this population. METHODS: In this observational cohort study, we studied self-reported pregnancies in two groups: seropositive people who had recovered from Ebola virus disease (seropositive group) and seronegative people who had close contact with people with Ebola (seronegative group). Participants had enrolled in the PREVAIL III longitudinal study and were exposed during the 2014-2016 Liberian Ebola outbreak. The primary outcome was pregnancy result. We assessed rates of livebirths and other pregnancy results in both study groups, and presence of Ebola RNA by PCR in samples of placenta, maternal and cord blood, breastmilk, and vaginal secretions from people who had recovered from Ebola who conceived a median of 14 months after acute Ebola virus disease. Mixed-model logistic regression evaluated associations between first-reported pregnancy outcome, age, and study group. Growth and neurodevelopment in the infants born to people in the seropositive group were assessed at 6-month intervals for 2 years. Data were accrued by PREVAIL III study staff. FINDINGS: 1566 participants were enrolled between June 17, 2015, and Dec 14, 2017, of whom 639 became pregnant (215 seropositive, 424 seronegative) and 589 reported pregnancy outcomes (206 seropositive, 383 seronegative). 105 infants born to 98 mothers in the seropositive group were enrolled in the birth cohort. Ebola RNA was not detected in 205 samples of placenta, cord blood, or maternal blood taken at birth from 54 mothers in the seropositive group, nor in 367 vaginal swabs. Viral RNA was found in two of 354 longitudinal breastmilk samples. All but one of 57 infants born during these 54 births were seropositive for anti-Ebola antibodies. Neonates showed high concentrations of anti-Ebola IgG, which declined after 6 months. Odds of adverse pregnancy outcome among the two groups were indistinguishable (OR 1·13, 95% CI 0·71-1·79). Compared with WHO standards, infants born to those in the seropositive group had lower median weight and length, and larger median head circumference over 2 years. Compared with a cohort from the USA accrual of gross motor developmental milestones was similar, whereas attainment of pincer grasp and early vocalisation were mildly delayed. INTERPRETATION: The risks of Ebola virus reactivation in the peripartum and postpartum period and of adverse birth outcomes are low in those who have recovered from Ebola virus disease and become pregnant approximately 1 year after acute Ebola virus disease. The implication for clinical practice is that care of people who are pregnant and who have recovered from Ebola can be offered without risks to health-care providers or stigmatisation of the mothers and their offspring. The implication for prospective mothers is that safe pregnancies are entirely possible after recovery from Ebola. FUNDING: National Institute of Allergy and Infectious Diseases and Liberia Ministry of Health.

Scalable, Micro-Neutralization Assay for Assessment of SARS-CoV-2 (COVID-19) Virus-Neutralizing Antibodies in Human Clinical Samples.

As the severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) pandemic expanded, it was clear that effective testing for the presence of neutralizing antibodies in the blood of convalescent patients would be critical for development of plasma-based therapeutic approaches. To address the need for a high-quality neutralization assay against SARS-CoV-2, a previously established fluorescence reduction neutralization assay (FRNA) against Middle East respiratory syndrome coronavirus (MERS-CoV) was modified and optimized. The SARS-CoV-2 FRNA provides a quantitative assessment of a large number of infected cells through use of a high-content imaging system. Because of this approach, and the fact that it does not involve subjective interpretation, this assay is more efficient and more accurate than other neutralization assays. In addition, the ability to set robust acceptance criteria for individual plates and specific test wells provided further rigor to this assay. Such agile adaptability avails use with multiple virus variants. By February 2021, the SARS-CoV-2 FRNA had been used to screen over 5000 samples, including acute and convalescent plasma or serum samples and therapeutic antibody treatments, for SARS-CoV-2 neutralizing titers.

Scalable, Micro-Neutralization Assay for Qualitative Assessment of SARS-CoV-2 (COVID-19) Virus-Neutralizing Antibodies in Human Clinical Samples.

As the severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) pandemic was expanding, it was clear that effective testing for the presence of neutralizing antibodies in the blood of convalescent patients would be critical for development of plasma-based therapeutic approaches. To address the need for a high-quality neutralization assay against SARS-CoV-2, a previously established fluorescence reduction neutralization assay (FRNA) against Middle East respiratory syndrome coronavirus (MERS-CoV) was modified and optimized. The SARS-CoV-2 FRNA provides a quantitative assessment of a large number of infected cells through use of a high-content imaging system. Because of this approach, and the fact that it does not involve subjective interpretation, this assay is more efficient and more accurate than other neutralization assays. In addition, the ability to set robust acceptance criteria for individual plates and specific test wells provided further rigor to this assay. Such agile adaptability avails use with multiple virus variants. By February 2021, the SARS-CoV-2 FRNA had been used to screen over 5,000 samples, including acute and convalescent plasma or serum samples and therapeutic antibody treatments, for SARS-CoV-2 neutralizing titers.