ABSTRACT
Background: Due to waning humoral immunity, a third COVID-19 vaccine dose is recommended but there is a lack of evidence regarding whether there is benefit to homologous versus heterologous mRNA vaccination. Method(s): This was a multi-centre parallel group randomized controlled trial in Toronto, Ontario from September 30, 2021 to May 13, 2022 which enrolled participants with stage 3B-5 chronic kidney disease with prior homologous mRNA two dose vaccination. Overall 273 participants were randomized 1:1 to either 30mug BNT162b2 (n=137) or 100 mug mRNA-1273 (n=136) third dose stratified by initial vaccine type. Neutralizing antibodies against the B.1.1.529 (Omicron) variant of concern as well as binding SARS-CoV-2 IgG antibodies to the spike protein, receptor binding domain, and nucleocapsid protein were measured. Result(s): Participants had a median age of 67 years, 94% were on dialysis, 3% had prior COVID-19, and 59% had received BNT162b2 for initial two dose vaccination. Prior to the third vaccine dose, detectable Omicron neutralizing antibodies were present in 2% with BNT162b2 and 54% with mRNA-1273 two dose vaccination. At 1 month post third dose, among those with baseline BNT162b2, Omicron-specific neutralizing antibodies were detectable in 84% with third dose BNT162b2 in comparison to 83% with third dose mRNA-1273 (p=0.70). In those with baseline mRNA-1273, 100% receiving third dose mRNA-1273 had Omicron-specific neutralizing antibodies in comparison to 96% with third dose BNT162b2 (p=0.75). During the study period, 9.3% of participants (n=25) contracted COVID-19 and two died from COVID-19 with no difference in infection based on vaccine type (p=0.26). Conclusion(s): In this randomized controlled trial of third dose COVID-19 vaccination, both homologous and heterologous vaccination elicited robust SARS-CoV-2 neutralizing antibody response. (Figure Presented).
ABSTRACT
INTRODUCTION: In response to two nosocomial clusters of coronavirus disease 2019 (COVID-19) in our hospital, we adopted a series of strict infection control measures, including regular rapid antigen test (RAT) screening for high-risk patients, visitors, and healthcare workers. We evaluated the diagnostic performance of a locally developed RAT, the INDICAID COVID-19 Rapid Antigen Test (Phase Scientific, Hong Kong), using respiratory samples from both symptomatic and asymptomatic individuals. METHODS: Real-time reverse-transcription polymerase chain reaction (rRT-PCR)-confirmed deep throat saliva (DTS) and pooled nasopharyngeal swab and throat swab (NPS/TS) samples collected from 1 November to 30 November 2020 were tested by INDICAID. Screening RATs were performed on asymptomatic healthcare workers during a 16-week period (1 December 2020 to 22 March 2021). RESULTS: In total, 20 rRT-PCR-confirmed samples (16 DTS, four pooled NPS/TS) were available for RAT. Using the original sample, RAT results were positive in 17/20 samples, indicating 85% sensitivity (95% confidence interval [CI]=62.11%-96.79%). Negative RAT results were associated with higher cycle threshold (Ct) values. For samples with Ct values <25, the sensitivity was 100%. Of the 49 801 RATs collected from healthcare workers, 33 false positives and one rRT-PCR-confirmed case were detected. The overall specificity was 99.93% (95% CI=99.91%-99.95%). The positive and negative predictive values were 2.94% (95% CI=2.11%-4.09%) and 100%, respectively. CONCLUSION: The INDICAID COVID-19 RAT demonstrated good sensitivity for specimens with high viral loads and satisfactory specificity for low-risk, asymptomatic healthcare workers.
Subject(s)
COVID-19 , COVID-19/diagnosis , COVID-19/epidemiology , Disease Outbreaks , Hong Kong/epidemiology , Hospitals, Private , Humans , SARS-CoV-2 , Sensitivity and SpecificityABSTRACT
Background: Hemodialysis (HD) patients have high mortality from COVID-19 and immunity following vaccination remains uncertain. This study evaluated SARS-CoV-2 antibody response in HD patients following BNT162b2 COVID-19 vaccination compared to health care workers (HCW) and convalescent serum. Methods: This single centre observational cohort study enrolled 142 HD patients and 35 HCW receiving the BNT162b2 vaccine. SARS-CoV-2 IgG antibodies to the spike protein (anti-spike), receptor binding domain (anti-RBD), and nucleocapsid protein (anti-NP) were measured in 66 HD patients receiving one vaccine dose, 76 HD patients receiving two vaccine doses, and 35 HCW receiving two vaccine doses. Results: In HD patients receiving a single BNT162b2 dose, seroconversion occurred in 53/66 (80%) for anti-spike and 35/66 (55%) for anti-RBD by 28 days post dose, but only 15/66 (23%) and 4/66 (6%), respectively attained a robust response defined as reaching the median level of anti-spike and anti-RBD in convalescent serum. In patients receiving two doses of BNT162b2 vaccine, seroconversion occurred in 69/72 (96%) for anti-spike and 63/72 (88%) for anti-RBD by 2 weeks following the second dose while 52/72 (72%) and 43/72 (60%) reached median convalescent serum levels of anti-spike and anti-RBD. In HCW, 35/35 (100%) exceeded median levels of anti-spike and anti-RBD in convalescent serum 2-4 weeks post second dose. Conclusions: This study found poor immunogenicity 28 days following a single dose of BNT162b2 vaccine in HD patients, supporting adherence to recommended vaccination schedules, and avoiding delay of the second dose in this population.