SARS-CoV-2 cross-sectional seroprevalence study among public school staff in Metro Vancouver after the first Omicron wave in British Columbia, Canada.

OBJECTIVE: To determine the SARS-CoV-2 seroprevalence among school workers within the Greater Vancouver area, British Columbia, Canada, after the first Omicron wave. DESIGN: Cross-sectional study by online questionnaire, with blood serology testing. SETTING: Three main school districts (Vancouver, Richmond and Delta) in the Vancouver metropolitan area. PARTICIPANTS: Active school staff enrolled from January to April 2022, with serology testing between 27 January and 8 April 2022. Seroprevalence estimates were compared with data obtained from Canadian blood donors weighted over the same sampling period, age, sex and postal code distribution. PRIMARY AND SECONDARY OUTCOMES: SARS-CoV-2 nucleocapsid antibody testing results adjusted for test sensitivity and specificity, and regional variation across school districts using Bayesian models. RESULTS: Of 1850 school staff enrolled, 65.8% (1214/1845) reported close contact with a COVID-19 case outside the household. Of those close contacts, 51.5% (625/1214) were a student and 54.9% (666/1214) were a coworker. Cumulative incidence of COVID-19 positive testing by self-reported nucleic acid or rapid antigen testing since the beginning of the pandemic was 15.8% (291/1845). In a representative sample of 1620 school staff who completed serology testing (87.6%), the adjusted seroprevalence was 26.5% (95% CrI 23.9% to 29.3%), compared with 32.4% (95% CrI 30.6% to 34.5%) among 7164 blood donors. CONCLUSION: Despite frequent COVID-19 exposures reported, SARS-CoV-2 seroprevalence among school staff in this setting remained no greater than the community reference group. Results are consistent with the premise that many infections were acquired outside the school setting, even with Omicron.

Effect of vaccine dosing intervals on Omicron surrogate neutralization after three doses of BNT162b2.

Background: Increasing the interval between the first and second SARS-CoV-2 vaccine doses enhances vaccine immunogenicity, however the optimal timing of the third vaccine is unknown. In this study, we investigated how the time interval between the first and second (V1-V2), or second and third (V2-V3) doses affects immunogenicity after three doses of the BNT162b2 (Comirnaty, Pfizer-BioNTech) vaccine. Methods: This is an observational cohort consisting of 360 participants enrolled in the COVID-19 Occupational Risks, Seroprevalence, and Immunity among Paramedics in Canada (CORSIP) study. Immune responses to BA.1 and other variants were measured from serum using an ACE2 competitive binding assay for surrogate SARS-CoV-2 neutralization. We fit a multiple linear regression model to estimate the independent association between both the V1-V2 and V2-V3 intervals and serum SARS-CoV-2 neutralization, while adjusting for age, sex, and the V3-to-blood collection interval. We examined vaccine dosing intervals as continuous variables and categorized them into quartiles. Results: The mean age was 40 years, 45% were female sex (at birth), and the median BA.1 surrogate neutralization was 61% (IQR 38-77%). The multivariate analysis indicated that longer V1-V2 (ß = 0.1292, 95% CI: 0.04807-0.2104) and V2-V3 (ß = 0.2653, 95% CI: 0.2291-0.3015) intervals were associated with increased surrogate neutralization of BA.1. These results were consistent when examining responses against Spike from other SARS-CoV-2 strains. When categorized into V2-V3 quartiles, the first (56-231 days), and second (231-266 days) quartiles demonstrated decreased BA.1 surrogate neutralization compared to the longest V2-V3 quartile (282-329 days). There was no significant difference in surrogate neutralization between the long (266-282 days) and longest (282-329 days) V2-V3 intervals. Conclusion: Longer intervals between first, second and third doses are independently associated with increased immunogenicity for all tested SARS-CoV-2 strains. Increasing the intervals between the second and third vaccine doses up to 8.9 months provided additive benefits increasing the immunogenicity of BNT162b2 vaccine schedules.

Are higher antibody levels against seasonal human coronaviruses associated with a more robust humoral immune response after SARS-CoV-2 vaccination?

The SARS-CoV-2 belongs to the coronavirus family, which also includes common endemic coronaviruses (HCoVs). We hypothesized that immunity to HCoVs would be associated with stronger immunogenicity from SARS-CoV-2 vaccines. The study included samples from the COSRIP observational cohort study of adult paramedics in Canada. Participants provided blood samples, questionnaire data, and results of COVID-19 testing. Samples were tested for anti-spike IgG against SARS-CoV-2, HCoV-229E, HCoV-HKU1, HCoV-NL63, and HCoV-OC43 antigens. We first compared samples from vaccinated and unvaccinated participants, to determine which HCoV antibodies were affected by vaccination. We created scatter plots and performed correlation analysis to estimate the extent of the linear relationship between HCoVs and SARS-CoV-2 anti-spike antibodies. Further, using adjusted log-log multiple regression, we modeled the association between each strain of HCoV and SARS-CoV-2 antibodies. Of 1510 participants (mean age of 39 years), 94 (6.2%) had a history of COVID-19. There were significant differences between vaccinated and unvaccinated participant in anti-spike antibodies to HCoV-HKU1, and HCoV-OC43; however, levels for HCoV-229E and HCoV-NL63 were similar (suggesting that vaccination did not affect these baseline values). Among vaccinated individuals without prior COVID-19 infection, SARS-COV-2 anti-spike IgG demonstrated a weak positive relationship between both HCoV-229E (r = 0.11) and HCoV-NL63 (r = 0.12). From the adjusted log-log multiple regression model, higher HCoV-229E and HCoV-NL63 anti-spike IgG antibodies were associated with increased SARS-COV-2 anti-spike IgG antibodies. Vaccination appears to result in measurable increases in HCoV-HKU1, and HCoV-OC43 IgG levels. Anti-HCoV-229E and HCoV-NL63 antibodies were unaffected by vaccination, and higher levels were associated with significantly higher COVID-19 vaccine-induced SARS-COV-2 antibodies.

Mental health and life satisfaction among Canadian paramedics during the COVID-19 pandemic: an update

IntroductionPrevious results suggest that COVID-19 adversely impacted a number of health and coping measures among Canadian paramedics, particularly females. Estimated prevalence for meeting screening criteria for mental health disorders and suicidal thoughts were higher than previously reported.ObjectivesTo provide an update on the impact of the COVID-19 pandemic on the wellbeing of Canadian paramedics with the inclusion of an additional year of participant data.MethodsSelf-reported questionnaire data was collected from paramedics across five Canadian provinces as part of the COVID-19 Occupational Risks, Seroprevalence and Immunity among Paramedics (CORSIP) project. Validated psychological assessment tools were used to screen for major depressive disorder (MDD, PHQ-9 questionnaire) and probable post-traumatic stress disorder (PTSD, PC-PTSD-5 questionnaire). Satisfaction with life (SWL) scores were adapted from validated Canadian Census questions and confirmed by reliability analysis. All measures were compared before versus during the pandemic using Wilcoxon signed-ranked, Cliff's d, and differences in proportions tests where appropriate.ResultsQuestionnaires from an additional 1662 recruited paramedics were included, now totaling 3568 participants. Prevalence meeting screening criteria remained similar for MDD (31.6%) and PTSD (41.4%), with PTSD risk continuing to not be impacted by COVID-19. Paramedics continued to report higher median SWL scores (20 vs. 17, p<.001) prior to the pandemic, with a large effect size (d=0.58) that suggests a greater probability of reporting higher SWL prior to COVID-19. Suicidal ideation (i.e., ‘thoughts that you would be better off dead, or of hurting yourself in some way') was reported by 9.0% of paramedics, which was consistent with original findings.ConclusionOriginal findings appear stable with the addition of another year of participant data. Future analyses will be employed to investigate whether health and satisfaction measures differed between the original cohort and added participants by adjusting for questionnaire responses with respect to the pandemic timeline.

Changes to infection prevention and control measures used by Canadian paramedics in response to COVID-19

IntroductionCanadian Paramedic services modified infection prevention and control (IPAC) practices in response to COVID-19. These changes may affect risk of exposure to infectious disease agents and can be used to inform future IPAC practices. We characterized COVID-19-related IPAC changes in the provinces of Alberta, British Columbia, Manitoba, Ontario, and Saskatchewan.Materials & MethodsQuestionnaire data (January 2021-Feb 2022) from the national COVID-19 Occupational Risks, Seroprevalence and Immunity among Paramedics (CORSIP) project was used to identify which IPAC practices were in place prior to COVID-19, and which were modified in response to COVID-19, including the timing of changes (March-May 2020;June-Aug 2020;Sept-Nov 2020;Nov 2020-present).Results2939 participants were included (146, 1249, 139, 1317, 88 from Alberta, BC, Manitoba, Ontario, and Saskatchewan, respectively), of whom 2674 (91%) reported receiving IPAC training. IPAC measures that were common prior to COVID-19 included: personal protective equipment (PPE) training, patient screening, hand hygiene, N95/P100 respirators, gowns, impermeable suits, and cleaning/disinfection. COVID-related IPAC changes included: screening staff, social distancing, restricting aerosol generating procedures, masking patients, cloth face coverings, surgical masks, face shields, and elastomeric respirators. Changes were reported for all IPAC measures. Most (71%) of these changes were made early in the COVID-19 pandemic (March-May 2020). Differences in proportions across provinces, community practice settings, and professional regulation status were reported (p < .05) for hand hygiene, PPE training, screening of patients, face shields, and various respirator types.ConclusionCanadian paramedic services were quick to modify available IPAC measures. However, these changes were variable across provinces, regulation status, and setting for specific IPAC measures. Inconsistent IPAC measures across jurisdictions may contribute to variable risk of infectious disease exposure. An evidence-informed and nationally coordinated approach may provide more equitable exposure risk mitigation for paramedic workers.

Effects of with holding treatment on mental health in Canadian paramedics during the COVID-19 pandemic

IntroductionPsychological effects of withholding treatment that could have benefited a patient during a pandemic remain largely unknown. It is also unclear to what extent their reasons for withholding treatment contributed to the subsequent impact on mental health outcomes. Paramedics may have withheld treatments either due to fear of exposure, being directed by their service, or both. As such, the present research aimed to characterize withholding treatment and investigate potential negative mental health outcomes.Materials and MethodsParamedics from five provinces (Alberta, British Columbia, Manitoba, Ontario, Saskatchewan) working during the COVID-19 pandemic completed online questionnaires assessing withholding treatment (i.e., due to fear of exposure, directed by their service, or both), and mental health outcomes including depression (PHQ-9) and post-traumatic stress (PTSD) symptoms (PC-PTSD-5) as part of the COVID-19 Occupational Risks, Seroprevalence and Immunity among Paramedics (CORSIP) study.ResultsOf the 1453 participants, 54.2% reported withholding treatment due to fear of exposure (4.3%), as directed by their service (76.5%) or both (19.2%). Participants who withheld treatment reported higher rates of PTSD (M=2.6, p < .01) and depression (M=8.2, p < .001) symptoms than those that did not withhold treatments (MPTSD=2.3;Mdepression=6.4). Reason for withholding treatment and PTSD symptom severity were associated (p<.01). Paramedics who withheld treatment due to fear of exposure were more likely to report probable PTSD symptoms (23.5%) than those who withheld treatments as directed by their service (8.7%) or both (12.2%). Depression symptom severity did not differ by reasons for withholding treatment.ConclusionsWithholding treatment is potentially traumatic and may influence the development of depression and PTSD symptoms. Withholding due to fear of exposure rather than being directed to increased PTSD symptoms. Further research will investigate the mental health impact of withholding treatment and reported reasons for withholding over time.

Extraction-free clinical detection of SARS-CoV-2 virus from saline gargle samples using Hamilton STARlet liquid handler.

As part of the COVID-19 pandemic, clinical laboratories have been faced with massive increases in testing, resulting in sample collection systems, reagent, and staff shortages. We utilized self-collected saline gargle samples to optimize high throughput SARS-CoV-2 multiplex polymerase chain reaction (PCR) testing in order to minimize cost and technologist time. This was achieved through elimination of nucleic acid extraction and automation of sample handling on a widely available robotic liquid handler, Hamilton STARlet. A customized barcode scanning script for reading the sample ID by the Hamilton STARlet's software system was developed to allow primary tube sampling. Use of pre-frozen SARS-CoV-2 assay reaction mixtures reduced assay setup time. In both validation and live testing, the assay produced no false positive or false negative results. Of the 1060 samples tested during validation, 3.6% (39/1060) of samples required retesting as they were either single gene positive, had internal control failure or liquid aspiration error. Although the overall turnaround time was only slightly faster in the automated workflow (185 min vs 200 min), there was a 76% reduction in hands-on time, potentially reducing staff fatigue and burnout. This described process from sample self-collection to automated direct PCR testing significantly reduces the total burden on healthcare systems in terms of human resources and reagent requirements.

Determining the Optimal SARS-CoV-2 mRNA Vaccine Dosing Interval for Maximum Immunogenicity.

OBJECTIVE: Emerging evidence indicates that longer SARS-CoV-2 vaccine dosing intervals results in an enhanced immune response. However, the optimal vaccine dosing interval for achieving maximum immunogenicity is unclear. METHODS: This study included samples from adult paramedics in Canada who received two doses of either BNT162b2 or mRNA-1273 vaccines and provided blood samples six months (170 to 190 days) after the first vaccine dose. The main exposure variable was vaccine dosing interval (days), categorized as "short" (first quartile), "moderate" (second quartile), "long" (third quartile), and "longest" interval (fourth quartile). The primary outcome was total spike antibody concentrations, measured using the Elecsys SARS-CoV-2 total antibody assay. Secondary outcomes included spike and receptor-binding domain (RBD) immunoglobulin G (IgG) antibody concentrations, and inhibition of angiotensin-converting enzyme 2 (ACE-2) binding to wild-type spike protein and several different Delta variant spike proteins. We fit a multiple log-linear regression model to investigate the association between vaccine dosing intervals and the antibody concentrations. RESULTS: A total of 564 adult paramedics (mean age 40 years, SD=10) were included. Compared to "short interval" (≤30 days), vaccine dosing intervals of the long (39-73 days) group (ß= 0.31, 95% Confidence interval (CI): 0.10-0.52) and the longest (≥74 days) group (ß = 0.82. 95% CI: 0.36-1.28) were associated with increased spike total antibody concentration. Compared to the short interval, the longest interval quartile was associated with higher spike IgG antibodies, while the long and longest intervals were associated with higher RBD IgG antibody concentrations. Similarly, the longest dosing intervals increased inhibition of ACE-2 binding to viral spike protein. CONCLUSION: Increased mRNA vaccine dosing intervals longer than 38 days result in higher levels of anti-spike antibodies and ACE-2 inhibition when assessed six months after the first COVID-19 vaccine.

The relationship between anti-spike SARS-CoV-2 antibody levels and risk of breakthrough COVID-19 among fully vaccinated adults.

The relationship between antibodies to wild-type SARS-CoV-2 antigens and the risk of breakthrough infections is unclear, especially during time periods of Omicron. We investigated the association of anti-spike and anti-receptor binding domain antibody levels and the risk of subsequent breakthrough COVID-19. We included adult paramedics from an observational cohort study who received ≥ 2 mRNA vaccines but did not have COVID-19 before the blood collection. Higher post-vaccine antibody levels to wild-type SARS-CoV-2 antigens were associated with a reduced risk of COVID-19. Further research into clinical utility of antibody levels, to inform a threshold for protection and timing of boosters, should be prioritized.

Characterizing intentions to receive the COVID-19 vaccine among the general population in British Columbia based on their future intentions towards the seasonal influenza vaccine.

Introduction: This study assessed the relationship between intention to receive a COVID-19 vaccine and intention to receive a seasonal influenza vaccine, as well as how intention to receive a COVID-19 vaccine has changed during the pandemic. Methods: Residents of British Columbia aged 25-69 years were invited to complete an online cross-sectional survey from August 2020 - March 2021. Mixed-effects logistic regression models assessed the relationship between intention to receive a COVID-19 vaccine and intention to receive the seasonal influenza vaccine. A generalized additive mixed model was used to investigate changes in COVID-19 vaccine intention during the pandemic (August 2020-March 2021). The relationship between intention to receive a COVID-19 vaccine and retrospective overall perceived value of vaccines prior to and during the pandemic was also considered. Results: Of 6,333 participants, 80.2 % of participants were 'somewhat or very likely' to receive a COVID-19 vaccine and 69 % of participants reported intending to receive a seasonal influenza vaccine. In multivariable modeling, intention to receive a COVID-19 vaccine was strongly associated with intention to receive a seasonal influenza vaccine (aOR = 4.25, 95 %CI 3.33-5.43). Intention to receive a COVID-19 vaccine increased over the study period (p < 0.0001), with the largest increase coinciding with the announcement of forthcoming approvals of COVID-19 vaccines in November 2020 (aOR = 1.45, 95 %CI 1.11-1.91). Conclusion: Intention to receive the COVID-19 vaccine was associated seasonal influenza vaccine intention, which is an important relationship to measure for implementation and future planning of COVID-19 booster doses. We found an increase in the intention to receive a COVID-19 vaccine after public announcements of forthcoming vaccine approval, which highlights the importance of ongoing monitoring and reporting of vaccine uptake, and the potential impact of emerging vaccine safety and efficacy information may have on vaccine acceptance.

Characterizing Longitudinal Antibody Responses in Recovered Individuals Following COVID-19 Infection and Single-Dose Vaccination: A Prospective Cohort Study.

BACKGROUND: Investigating antibody titers in individuals who have been both naturally infected with SARS-CoV-2 and vaccinated can provide insight into antibody dynamics and correlates of protection over time. METHODS: Human coronavirus (HCoV) IgG antibodies were measured longitudinally in a prospective cohort of qPCR-confirmed, COVID-19 recovered individuals (k = 57) in British Columbia pre- and post-vaccination. SARS-CoV-2 and endemic HCoV antibodies were measured in serum collected between Nov. 2020 and Sept. 2021 (n = 341). Primary analysis used a linear mixed-effects model to understand the effect of single dose vaccination on antibody concentrations adjusting for biological sex, age, time from infection and vaccination. Secondary analysis investigated the cumulative incidence of high SARS-CoV-2 anti-spike IgG seroreactivity equal to or greater than 5.5 log10 AU/mL up to 105 days post-vaccination. No re-infections were detected in vaccinated participants, post-vaccination by qPCR performed on self-collected nasopharyngeal specimens. RESULTS: Bivariate analysis (complete data for 42 participants, 270 samples over 472 days) found SARS-CoV-2 spike and RBD antibodies increased 14-56 days post-vaccination (p < 0.001) and vaccination prevented waning (regression coefficient, B = 1.66 [95%CI: 1.45-3.46]); while decline of nucleocapsid antibodies over time was observed (regression coefficient, B = -0.24 [95%CI: -1.2-(-0.12)]). A positive association was found between COVID-19 vaccination and endemic human ß-coronavirus IgG titer 14-56 days post vaccination (OC43, p = 0.02 & HKU1, p = 0.02). On average, SARS-CoV-2 anti-spike IgG concentration increased in participants who received one vaccine dose by 2.06 log10 AU/mL (95%CI: 1.45-3.46) adjusting for age, biological sex, and time since infection. Cumulative incidence of high SARS-CoV-2 spike antibodies (>5.5 log10 AU/mL) was 83% greater in vaccinated compared to unvaccinated individuals. CONCLUSIONS: Our study confirms that vaccination post-SARS-CoV-2 infection provides multiple benefits, such as increasing anti-spike IgG titers and preventing decay up to 85 days post-vaccination.

Are higher antibody levels against seasonal human coronaviruses associated with a more robust humoral immune response after SARS-CoV-2 vaccination?

The SARS-CoV-2 belongs to the coronavirus family, which also includes common endemic coronaviruses (HCoVs). We hypothesized that immunity to HCoVs would be associated with stronger immunogenicity from SARS-CoV-2 vaccines. The study included samples from the COSRIP observational cohort study of adult paramedics in Canada. Participants provided blood samples, questionnaire data, and results of COVID-19 testing. Samples were tested for anti-spike IgG against SARS-CoV-2, HCoV-229E, HCoV-HKU1, HCoV-NL63, and HCoV-OC43 antigens. We first compared samples from vaccinated and unvaccinated participants, to determine which HCoV antibodies were affected by vaccination. We created scatter plots and performed correlation analysis to estimate the extent of the linear relationship between HCoVs and SARS-CoV-2 anti-spike antibodies. Further, using adjusted log-log multiple regression, we modeled the association between each strain of HCoV and SARS-CoV-2 antibodies. Of 1510 participants (mean age of 39 years), 94 (6.2%) had a history of COVID-19. There were significant differences between vaccinated and unvaccinated participant in anti-spike antibodies to HCoV-HKU1, and HCoV-OC43;however, levels for HCoV-229E and HCoV-NL63 were similar (suggesting that vaccination did not affect these baseline values). Among vaccinated individuals without prior COVID-19 infection, SARS-COV-2 anti-spike IgG demonstrated a weak positive relationship between both HCoV-229E (r = 0.11) and HCoV-NL63 (r = 0.12). From the adjusted log-log multiple regression model, higher HCoV-229E and HCoV-NL63 anti-spike IgG antibodies were associated with increased SARS-COV-2 anti-spike IgG antibodies. Vaccination appears to result in measurable increases in HCoV-HKU1, and HCoV-OC43 IgG levels. Anti-HCoV-229E and HCoV-NL63 antibodies were unaffected by vaccination, and higher levels were associated with significantly higher COVID-19 vaccine-induced SARS-COV-2 antibodies.

Correlation of SARS-CoV-2 Viral Neutralizing Antibody Titers with Anti-Spike Antibodies and ACE-2 Inhibition among Vaccinated Individuals.

SARS-CoV-2 anti-spike antibody concentrations and angiotensin converting enzyme-2 (ACE-2) inhibition have been used as surrogates to live viral neutralizing antibody titers; however, validity among vaccinated individuals is unclear. We tested the correlation of these measures among vaccinated participants, and examined subgroups based on duration since vaccination and vaccine dosing intervals. We analyzed 120 samples from two-dose mRNA vaccinees without previous COVID-19. We calculated Spearman correlation coefficients between wild-type viral neutralizing antibody titers and: anti-spike (total and IgG), anti-receptor-binding-domain (RBD), and anti-N-terminal-domain (NTD) antibodies; and ACE-2 binding by RBD. We performed three secondary analyses, dichotomizing samples by the first vaccination-to-blood collection interval, second vaccination-to-blood collection interval, and by the vaccine dosing interval (all groups divided by the median), and compared correlation coefficients (Fisher's Z test). Of 120 participants, 63 (53%) were women, 91 (76%) and 29 (24%) received BNT162b2 and mRNA-1273 vaccines, respectively. Overall, live viral neutralization was correlated with anti-spike total antibody (correlation coefficient = 0.80), anti-spike IgG (0.63), anti-RBD IgG (0.62), anti-NTD IgG (0.64), and RBD ACE2 binding (0.65). Samples with long (>158 days) first vaccination-to-blood collection and long (>71 days) second vaccination-to-blood collection intervals demonstrated higher correlation coefficients, compared with short groups. When comparing cases divided by short (≤39 days) versus long vaccine dosing intervals, only correlation with RBD-ACE-2 binding inhibition was higher in the long group. Among COVID-negative mRNA vaccinees, anti-spike antibody and ACE-2 inhibition concentrations are correlated with live viral neutralizing antibody titers. Correlation was stronger among samples collected at later durations from vaccination. IMPORTANCE Live viral neutralizing antibody titers are an accepted measure of immunity; however, testing procedures are labor-intensive. COVID-19 antibody and angiotensin converting enzyme-2 (ACE-2) levels have been used as surrogates to live viral neutralizing antibody titers; however, validity among vaccinated individuals is unclear. Using samples from 120 two-dose mRNA vaccinees without previous COVID-19, we found that live viral neutralization was correlated with COVID-19 antibody and ACE2 binding levels. When grouping samples by the time interval between vaccination and sample blood collection, samples collected over 158 days after the first vaccine and over 71 days from the second vaccine demonstrated stronger correlation between live viral neutralization titers and both antibody and ACE2 levels, in comparison to those collected earlier.

Seropositivity of SARS-CoV-2 in an unvaccinated cohort in British Columbia, Canada: a cross-sectional survey with dried blood spot samples.

OBJECTIVES: Gathering population-based data on prevalence of SARS-CoV-2 infection is vital to the public health response and planning. Current seroprevalence data in BC are limited with respect to considerations of how socioeconomic and demographic factors, such as age, sex, gender, income, identifying as a visibility minority and occupation, are related to SARS-CoV-2 antibody detection due to infection-acquired immunity. We aimed to estimate the SARS-CoV-2 seropositivity in a cohort of British Columbians, using at-home self-collected dried blood spot (DBS) samples. DESIGN: This cross-sectional study included online surveys that collected sociodemographic and COVID-19 vaccine receipt information, and an at-home DBS collection kit. SETTING: British Columbia (BC), Canada. PARTICIPANTS: Eligible participants were aged 25-69 years and residents of BC. PRIMARY OUTCOME MEASURE: SARS-CoV-2 anti-spike IgG antibody detection in unvaccinated individuals. Adjusted incidence rate ratios (aIRR) explored factors associated with seropositivity. RESULTS: SARS-CoV-2 serology was performed on a total of 4048 unvaccinated participants 25-69 years of age who submitted DBS samples taken from November 2020 to June 2021. A total of 118 seropositive cases were identified, for an estimated overall seropositivity of 2.92% (95% CI 2.42% to 3.48%). Participants identifying as a visible minority had a higher seropositivity, 5.1% vs 2.6% (p=0.003), compared with non-visible minority participants. After adjustment by age and sex, identifying as a visible minority (aIRR=1.85, 95% CI 1.20 to 2.84) remained the only significant factor associated with SARS-CoV-2 antibody detection in this cohort of unvaccinated individuals. CONCLUSIONS: SARS-CoV-2 seropositivity in the BC population due to infection-acquired immunity was low. Seropositivity indicated that among those unvaccinated, visible minority communities have been most impacted. Continued monitoring of SARS-CoV-2 serology due to both infection-acquired and vaccine-acquired immunity will be vital in public health planning and pandemic response.

Characterizing intentions to receive the COVID-19 vaccine among the general population in British Columbia based on their future intentions towards the seasonal influenza vaccine

Introduction This study assessed the relationship between intention to receive a COVID-19 vaccine and intention to receive a seasonal influenza vaccine, as well as how intention to receive a COVID-19 vaccine has changed during the pandemic. Methods Residents of British Columbia aged 25-69 years were invited to complete an online cross-sectional survey from August 2020 - March 2021. Mixed-effects logistic regression models assessed the relationship between intention to receive a COVID-19 vaccine and intention to receive the seasonal influenza vaccine. A generalized additive mixed model was used to investigate changes in COVID-19 vaccine intention during the pandemic (August 2020 – March 2021). The relationship between intention to receive a COVID-19 vaccine and retrospective overall perceived value of vaccines prior to and during the pandemic was also considered. Results Of 6,333 participants, 80.2% of participants were ‘somewhat or very likely’ to receive a COVID-19 vaccine and 69% of participants reported intending to receive a seasonal influenza vaccine. In multivariable modeling, intention to receive a COVID-19 vaccine was strongly associated with intention to receive a seasonal influenza vaccine (OR=4.25, 95%CI 3.33 - 5.43). Intention to receive a COVID-19 vaccine increased over the study period (p<0.0001), with the largest increase coinciding with the announcement of forthcoming approvals of COVID-19 vaccines in November 2020 (OR = 1.45, 95%CI 1.11 - 1.91). Conclusion Intention to receive the COVID-19 vaccine was associated seasonal influenza vaccine intention, which is an important relationship to measure for implementation and future planning of COVID-19 booster doses. We found an increase in the intention to receive a COVID-19 vaccine after public announcements of forthcoming vaccine approval, which highlights the importance of ongoing monitoring and reporting of vaccine uptake, and the potential impact of emerging vaccine safety and efficacy information may have on vaccine acceptance.

Sensitivity of the Elecsys Nucleocapsid Assay for the Detection of Preceding SARS-CoV-2 Infections.

Nucleocapsid serological assay sensitivity to identify severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) infections among vaccinees and for Omicron cases is unclear. In this prospective study, the Elecsys nucleocapsid assay was 89% sensitive in identifying SARS-CoV-2 infections 14-607 days pre-blood collection. Sensitivity was similar when comparing by vaccination status, and in Omicron (vs pre-Omicron) cases.

SARS-CoV-2 seroprevalence among Vancouver public school staff in British Columbia, Canada: a cross-sectional study.

OBJECTIVES: Few studies reported COVID-19 cases in schools during the 2020/21 academic year in a setting of uninterrupted in-person schooling. The main objective was to determine the SARS-CoV-2 seroprevalence among school staff in Vancouver public schools. DESIGN: Cumulative incident COVID-19 cases among all students and school staff based on public health data, with an embedded cross-sectional serosurvey among a school staff sample that was compared to period, age, sex and geographical location-weighted data from blood donors. SETTING: Vancouver School District (British Columbia, Canada) from kindergarten to grade 12. PARTICIPANTS: Active school staff enrolled from 3 February to 23 April 2021 with serology testing from 10 February to 15 May 2021. MAIN OUTCOME MEASURES: SARS-CoV-2 seroprevalence among school staff, based on spike (S)-based (unvaccinated staff) or N-based serology testing (vaccinated staff). RESULTS: Public health data showed the cumulative incidence of COVID-19 among students attending in-person was 9.8 per 1000 students (n=47 280), and 13 per 1000 among school staff (n=7071). In a representative sample of 1689 school staff, 78.2% had classroom responsibilities, and spent a median of 17.6 hours in class per week (IQR: 5.0-25 hours). Although 21.5% (363/1686) of surveyed staff self-reported close contact with a COVID-19 case outside of their household (16.5% contacts were school-based), 5 cases likely acquired the infection at school based on viral testing. Sensitivity/Specificity-adjusted seroprevalence in 1556/1689 staff (92.1%) was 2.3% (95% CI: 1.6% to 3.2%), comparable to a sex, age, date and residency area-weighted seroprevalence of 2.6% (95% CI: 2.2% to 3.1%) among 5417 blood donors. CONCLUSION: Seroprevalence among staff was comparable to a reference group of blood donors from the same community. These data show that in-person schooling could be safely maintained during the 2020/21 school year with mitigation measures, in a large school district in Vancouver, Canada.

Risk Factors for COVID-19 in a Retired FDNY WTC-Exposed Cohort.

We evaluated the incidence and risk factors for COVID-19 in a prospectively followed cohort of Fire Department of the City of New York (FDNY) World Trade Center (WTC)-exposed workers, thus reducing the potential for selection bias, a limitation in published studies of hospitalized individuals. Participants were retired FDNY WTC-exposed rescue/recovery workers with ≥1 medical visit between 1 March 2020 and 1 August 2021. The cumulative incidence was calculated using self-reported COVID-19 diagnoses. Cox regression was performed to evaluate the association of WTC-exposure and COVID-19, adjusting for history of comorbidities, age, race, work assignment (emergency medical service providers vs. firefighter), and sex. The cumulative incidence of COVID-19 was 130 per 1000. The adjusted models showed the risk of infection was greater in those with highest WTC exposure versus less exposure (hazard ratio (HR) = 1.14 (95% CI 1.00-1.31)). Older age was associated with a lower risk of infection HR = 0.97 (95% CI 0.96-0.98). WTC-associated diseases (obstructive airways disease and interstitial lung disease) were not COVID-19 risk factors. This study is the first to show an association between WTC exposure and the risk of COVID-19. While participants are retired from FDNY work, the youngest individuals may still be in the workforce, explaining why younger age was a significant risk for COVID-19.