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1.
Front Med (Lausanne) ; 8: 758118, 2021.
Article in English | MEDLINE | ID: covidwho-1709387

ABSTRACT

Background: In October 2020 SARS-CoV-2 seroprevalence among hospital healthcare workers (HCW) of two Irish hospitals was 15 and 4. 1%, respectively. We compare seroprevalence in the same HCW population 6 months later, assess changes in risk factors for seropositivity with progression of the pandemic and serological response to vaccination. Methods: All staff of both hospitals (N = 9,038) were invited to participate in an online questionnaire and SARS-CoV-2 antibody testing in April 2021. We measured anti-nucleocapsid and anti-spike antibodies. Frequencies and percentages for positive SARS-CoV-2 antibodies were calculated and adjusted relative risks for participant characteristics were calculated using multivariable regression analysis. Results: Five thousand and eighty-five HCW participated. Seroprevalence increased to 21 and 13%, respectively; 26% of infections were previously undiagnosed. Black ethnicity (aRR 1.7, 95% CI 1.3-2.2, p < 0.001), lower level of education (aRR 1.4 for secondary level education, 95% CI 1.1-1.8, p = 0.002), living with other HCW (aRR 1.2, 95% CI 1.0-1.4, p = 0.007) were significantly associated with seropositivity. Having direct patient contact also carried a significant risk being a healthcare assistant (aRR 1.8, 95% CI 1.3-2.3, p < 0.001), being a nurse (aRR 1.4, 95% CI 1.0-1.8, p = 0.022), daily contact with COVID-19 patients (aRR 1.4, 95% CI 1.1-1.7, p = 0.002), daily contact with patients without suspected or confirmed COVID-19 (aRR 1.3, 95% CI 1.1-1.5, p = 0.013). Breakthrough infection occurred in 23/4,111(0.6%) of fully vaccinated participants; all had anti-S antibodies. Conclusion: The increase in seroprevalence reflects the magnitude of the third wave of the pandemic in Ireland. Genomic sequencing is needed to apportion risk to the workplace vs. the household/community. Concerted efforts are needed to mitigate risk factors due to ethnicity and lower level of education, even at this stage of the pandemic. The undiagnosed and breakthrough infections call for ongoing infection prevention and control measures and testing of HCW in the setting of close contact. Vaccinated HCW with confirmed infection should be actively assessed, including SARS-CoV-2 whole genome sequencing (WGS), serology testing and assessment of host determinants, to advance understanding of the reasons for breakthrough infection.

2.
EuropePMC; 2020.
Preprint in English | EuropePMC | ID: ppcovidwho-316748

ABSTRACT

SARS-CoV-2 continues to widely circulate in populations globally. Underdetection is acknowledged and is problematic when attempting to capture the true prevalence. Seroprevalence studies, where blood samples from a population sample are tested for SARS-CoV-2 antibodies that react to the SARS-CoV-2 virus, are a common method for estimating the proportion of people previously infected with the virus in a given population. However, obtaining reliable estimates from seroprevalence studies is challenging for a number of reasons, and the uncertainty in the results is often overlooked by scientists, policy makers and the media. This paper reviews the methodological issues that arise in designing these studies, and the main sources of uncertainty that affect the results. We discuss the choice of study population, recruitment of subjects, uncertainty surrounding the accuracy of antibody tests themselves, and the relationship between antibodies and infection over time. Understanding these issues can help the reader to interpret and critically evaluate the results of seroprevalence studies.

3.
EuropePMC; 2021.
Preprint in English | EuropePMC | ID: ppcovidwho-316727

ABSTRACT

Background: The serial interval is the period of time between the onset of symptoms in an infector and an infectee and is an important parameter which can impact on the estimation of the reproduction number. Whilst several parameters influencing infection transmission are expected to be consistent across populations, the serial interval can vary across and within populations over time. Therefore, local estimates are preferable for use in epidemiological models developed at a regional level. We used data collected as part of the national contact tracing process in Ireland to estimate the serial interval of SARS-CoV-2 infection in the Irish population, and to estimate the proportion of transmission events that occurred prior to the onset of symptoms. Results: After data cleaning, the final dataset consisted of 471 infected close contacts from 471 primary cases. The mean serial interval was 4.0 (95% confidence intervals 3.75, 4.31) days, whilst the 25 th , 50 th and 75 th percentiles were 2, 4 and 6 days respectively. We found that intervals were lower when the primary or secondary case were in the older age cohort (greater than 64 years). Simulating from an incubation period distribution from international literature, we estimated that 67% of transmission events had greater than 50% probability of occurring prior to the onset of symptoms in the infector. Conclusions: Whilst our analysis was based on a large sample size, data were collected for the primary purpose of interrupting transmission chains. Similar to other studies estimating the serial interval, our analysis is restricted to transmission pairs where the infector is known with some degree of certainty. Such pairs may represent more intense contacts with infected individuals than might occur in the overall population. It is therefore possible that our analysis is biased towards shorter serial intervals than the overall population.

4.
EuropePMC; 2021.
Preprint in English | EuropePMC | ID: ppcovidwho-305332

ABSTRACT

Background: In October 2020 SARS-CoV-2 seroprevalence among hospital healthcare workers (HCW) of two Irish hospitals was 15% and 4.1% respectively. We compare seroprevalence in the same HCW population six months later, assess changes in risk factors for seropositivity with progression of the pandemic and serological response to vaccination.Methods: All staff of both hospitals (N=9038) were invited to participate in an online questionnaire and SARS-CoV-2 antibody testing in April 2021. We measured anti-nucleocapsid and anti-spike antibodies. Frequencies and percentages for positive SARS-CoV-2 antibodies were calculated and adjusted relative risks for participant characteristics were calculated using multivariable regression analysis. ­ Findings: 5085 HCW participated. Seroprevalence increased to 21% and 13% respectively;26% of infections were previously undiagnosed. Black ethnicity, lower level of education, living with other HCW, and direct patient contact were significantly associated with seropositivity (p<.001). Breakthrough infection occurred in 23/4111(0.6%) of fully vaccinated participants;all had anti-S antibodies.Interpretation: The increase in seroprevalence reflects the magnitude of the third wave of the pandemic in Ireland. Genomic sequencing is needed to apportion risk to the workplace versus the household/community. Concerted efforts are needed to mitigate risk factors due to ethnicity and lower level of education, even at this stage of the pandemic. The undiagnosed and breakthrough infections call for ongoing infection prevention and control measures and testing of HCW in the setting of close contact. Vaccinated HCW with confirmed infection should be actively assessed, including SARS-CoV-2 whole genome sequencing (WGS), serology testing and assessment of host determinants, to advance understanding of the reasons for breakthrough infection.Funding: This work was supported financially by the Irish Health Service Executive COVID-19budget.Declaration of Interest: None to declare. Ethical Approval: Ethical approval was obtained from the National Research Ethics Committee (NREC) for COVID-19, Study Number 20-NREC. COV-101 (33).

5.
BMC Public Health ; 21(1): 2238, 2021 12 09.
Article in English | MEDLINE | ID: covidwho-1566516

ABSTRACT

BACKGROUND: Contact tracing is conducted with the primary purpose of interrupting transmission from individuals who are likely to be infectious to others. Secondary analyses of data on the numbers of close contacts of confirmed cases could also: provide an early signal of increases in contact patterns that might precede larger than expected case numbers; evaluate the impact of government interventions on the number of contacts of confirmed cases; or provide data information on contact rates between age cohorts for the purpose of epidemiological modelling. We analysed data from 140,204 close contacts of 39,861 cases in Ireland from 1st May to 1st December 2020. RESULTS: Negative binomial regression models highlighted greater numbers of contacts within specific population demographics, after correcting for temporal associations. Separate segmented regression models of the number of cases over time and the average number of contacts per case indicated that a breakpoint indicating a rapid decrease in the number of contacts per case in October 2020 preceded a breakpoint indicating a reduction in the number of cases by 11 days. CONCLUSIONS: We found that the number of contacts per infected case was overdispersed, the mean varied considerable over time and was temporally associated with government interventions. Analysis of the reported number of contacts per individual in contact tracing data may be a useful early indicator of changes in behaviour in response to, or indeed despite, government restrictions. This study provides useful information for triangulating assumptions regarding the contact mixing rates between different age cohorts for epidemiological modelling.


Subject(s)
COVID-19 , SARS-CoV-2 , Contact Tracing , Government , Humans , Ireland
6.
Vaccine ; 39(40): 5954-5962, 2021 09 24.
Article in English | MEDLINE | ID: covidwho-1372608

ABSTRACT

The influenza vaccine is free to all healthcare workers (HCWs) working in hospitals and long-term/residential health care facilities in Ireland. To evaluate influenza vaccine uptake, the Health Service Executive-Health Protection Surveillance Centre surveyed HCWs each season between 2011-2012 and 2019-2020. The national HCW uptake target was 40% for the first six seasons and was increased to 75% for the 2019-2020 season. Data on seasonal influenza vaccine uptake among HCWs employed in these healthcare settings were obtained using web-based surveys sent to occupational or management contact points. Data on numbers of staff vaccinated by Health Service Executive (HSE) professional staff grade and numbers eligible for vaccination in each grade were provided. Since the 2017-2018 season, a point prevalence survey for residents to assess influenza vaccine uptake has also been undertaken in long-term/residential care facilities (LTCFs) and aggregate data submitted, initially using a desktop spreadsheet survey tool, but later using web-based survey tools; these surveys were undertaken to investigate how uptake differed between HCWs and residents, both long-term and short-term. Participation by healthcare facilities and influenza vaccine uptake by both HCWs and LTCF-residents in these surveys increased over the nine seasons. Uptake among HCWs employed in publicly-funded hospitals increased from 18.1% (2011-2012) to 58.9% (2019-2020). Uptake in publicly-funded LTCFs increased from 17.8% (2011-2012) to 45.5% (2019-2020). Overall, uptake among hospital nursing staff was lowest among all staff categories for most seasons, but increased from 12.4% in 2011-2012 to 58.1% in 2019-2020. In all seasons since 2011-2012, medical/dental, management/administrative or health and social care professional staff reported the highest uptake values in public LTCFs. Of the three annual point prevalence surveys between 2017-2018 and 2019-2020, all showed high overall uptake among long-term residents (between 88.9% and 89.4%), and a lower and wider uptake range among respite residents (between 57.5% and 66.5%).


Subject(s)
Influenza Vaccines , Influenza, Human , Health Personnel , Humans , Influenza, Human/epidemiology , Influenza, Human/prevention & control , Ireland/epidemiology , Public Health , Seasons
7.
Microbiol Spectr ; 9(2): e0039121, 2021 10 31.
Article in English | MEDLINE | ID: covidwho-1443360

ABSTRACT

Severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) antibodies are an excellent indicator of past COVID-19 infection. As the COVID-19 pandemic progresses, retained sensitivity over time is an important quality in an antibody assay that is to be used for the purpose of population seroprevalence studies. We compared 5,788 health care worker (HCW) serum samples by using two serological assays (Abbott SARS-CoV-2 anti-nucleocapsid immunoglobulin G (IgG) and Roche anti-SARS-CoV-2 anti-nucleocapsid total antibody) and a subset of samples (all Abbott assay positive or grayzone, n = 485) on Wantai SARS-CoV-2 anti-spike antibody enzyme-linked immunosorbent assay (ELISA). For 367 samples from HCW with a previous PCR-confirmed SARS-CoV-2 infection, we correlated the timing of infection with assay results. Overall, seroprevalence was 4.2% on Abbott and 9.5% on Roche. Of those with previously confirmed infection, 41% (150/367) and 95% (348/367) tested positive on Abbott and Roche, respectively. At 21 weeks (150 days) after confirmed infection, positivity on Abbott started to decline. Roche positivity was retained for the entire study period (33 weeks). Factors associated (P ≤ 0.050) with Abbott seronegativity in those with previous PCR-confirmed infection included sex (odds ratio [OR], 0.30 male ; 95% confidence interval [CI], 0.15 to 0.60), symptom severity (OR 0.19 severe symptoms; 95% CI, 0.05 to 0.61), ethnicity (OR, 0.28 Asian ethnicity; 95% CI, 0.12 to 0.60), and time since PCR diagnosis (OR, 2.06 for infection 6 months previously; 95% CI, 1.01 to 4.30). Wantai detected all previously confirmed infections. In our population, Roche detected antibodies up to at least 7 months after natural infection with SARS-CoV-2. This finding indicates that the Roche total antibody assay is better suited than Abbott IgG assay to population-based studies. Wantai demonstrated high sensitivity, but sample selection was biased. The relationship between serological response and functional immunity to SARS-CoV-2 infection needs to be delineated. IMPORTANCE As the COVID-19 pandemic progresses, retained sensitivity over time is an important quality in an antibody assay that is to be used for the purpose of population seroprevalence studies. There is a relative paucity of published literature in this field to help guide public health specialists when planning seroprevalence studies. In this study, we compared results of 5,788 health care worker blood samples tested by using two assays (Roche and Elecsys, anti-nucleocapsid antibody) and by testing a subset on a third assay (Wantai enzyme-linked immunosorbent assay [ELISA] anti-spike antibody). We found significant differences in the performance of these assays, especially with distance in time from PCR-confirmed COVID-19 infection, and we feel these results may significantly impact the choice of assay for others conducting similar studies.


Subject(s)
Antibodies, Viral/blood , COVID-19 Serological Testing/methods , COVID-19/diagnosis , Coronavirus Nucleocapsid Proteins/immunology , SARS-CoV-2/immunology , Spike Glycoprotein, Coronavirus/immunology , Adult , Cross-Sectional Studies , Enzyme-Linked Immunosorbent Assay , Female , Health Personnel/statistics & numerical data , Humans , Immunoglobulin G/blood , Male , Middle Aged , Phosphoproteins/immunology , Sensitivity and Specificity , Seroepidemiologic Studies , Young Adult
8.
Int J Environ Res Public Health ; 18(9)2021 04 27.
Article in English | MEDLINE | ID: covidwho-1389363

ABSTRACT

SARS-CoV-2 continues to widely circulate in populations globally. Underdetection is acknowledged and is problematic when attempting to capture the true prevalence. Seroprevalence studies, where blood samples from a population sample are tested for SARS-CoV-2 antibodies that react to the SARS-CoV-2 virus, are a common method for estimating the proportion of people previously infected with the virus in a given population. However, obtaining reliable estimates from seroprevalence studies is challenging for a number of reasons, and the uncertainty in the results is often overlooked by scientists, policy makers, and the media. This paper reviews the methodological issues that arise in designing these studies, and the main sources of uncertainty that affect the results. We discuss the choice of study population, recruitment of subjects, uncertainty surrounding the accuracy of antibody tests, and the relationship between antibodies and infection over time. Understanding these issues can help the reader to interpret and critically evaluate the results of seroprevalence studies.


Subject(s)
COVID-19 , SARS-CoV-2 , Antibodies, Viral , Humans , Prevalence , Seroepidemiologic Studies , Uncertainty
10.
Int J Environ Res Public Health ; 18(12)2021 06 10.
Article in English | MEDLINE | ID: covidwho-1264459

ABSTRACT

Like most countries worldwide, the coronavirus disease (COVID-19) has adversely affected Ireland. The aim of this study was to (i) investigate the spatio-temporal trend of COVID-19 incidence; (ii) describe mobility trends as measured by aggregated mobile phone records; and (iii) investigate the association between deprivation index, population density and COVID-19 cases while accounting for spatial and temporal correlation. Standardised incidence ratios of cases were calculated and mapped at a high spatial resolution (electoral division level) over time. Trends in the percentage change in mobility compared to a pre-COVID-19 period were plotted to investigate the impact of lockdown restrictions. We implemented a hierarchical Bayesian spatio-temporal model (Besag, York and Mollié (BYM)), commonly used for disease mapping, to investigate the association between covariates and the number of cases. There have been three distinct "waves" of COVID-19 cases in Ireland to date. Lockdown restrictions led to a substantial reduction in human movement, particularly during the 1st and 3rd wave. Despite adjustment for population density (incidence ratio (IR) = 1.985 (1.915-2.058)) and the average number of persons per room (IR = 10.411 (5.264-22.533)), we found an association between deprivation index and COVID-19 incidence (IR = 1.210 (CI: 1.077-1.357) for the most deprived quintile compared to the least deprived). There is a large range of spatial heterogeneity in COVID-19 cases in Ireland. The methods presented can be used to explore locally intensive surveillance with the possibility of localised lockdown measures to curb the transmission of infection, while keeping other, low-incidence areas open. Our results suggest that prioritising densely populated deprived areas (that are at increased risk of comorbidities) during vaccination rollout may capture people that are at risk of infection and, potentially, also those at increased risk of hospitalisation.


Subject(s)
COVID-19 , Bayes Theorem , Communicable Disease Control , Humans , Ireland/epidemiology , SARS-CoV-2
11.
BJGP Open ; 5(4)2021 Aug.
Article in English | MEDLINE | ID: covidwho-1234851

ABSTRACT

BACKGROUND: Severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) antibody testing in community settings may help us better understand the immune response to this virus and, therefore, help guide public health efforts. AIM: To conduct a seroprevalence study of immunoglobulin G (IgG) antibodies in Irish GP clinics. DESIGN & SETTING: Participants were 172 staff and 799 patients from 15 general practices in the Midwest region of Ireland. METHOD: This seroprevalence study utilised two manufacturers' point-of-care (POC) SARS-CoV-2 immunoglobulin M (IgM)-IgG combined antibody tests, which were offered to patients and staff in general practice from 15 June to 10 July 2020. RESULTS: IgG seroprevalence was 12.6% in patients attending general practice and 11.1% in staff working in general practice, with administrative staff having the lowest seroprevalence at 2.5% and nursing staff having the highest at 17.6%. Previous symptoms suggestive of COVID-19 and history of a polymerase chain reaction (PCR) test were associated with higher seroprevalence. IgG antibodies were detected in approximately 80% of participants who had a previous PCR-confirmed infection. Average length of time between participants' positive PCR test and positive IgG antibody test was 83 days. CONCLUSION: Patients and healthcare staff in general practice in Ireland had relatively high rates of IgG to SARS-CoV-2 compared with the national average between 15 June and 10 July 2020 (1.7%). Four-fifths of participants with a history of confirmed COVID-19 disease still had detectable antibodies an average of 12 weeks post-infection. While not proof of immunity, SARS-CoV-2 POC testing can be used to estimate IgG seroprevalence in general practice settings.

12.
BMC Public Health ; 21(1): 805, 2021 04 27.
Article in English | MEDLINE | ID: covidwho-1204065

ABSTRACT

BACKGROUND: The serial interval is the period of time between the onset of symptoms in an infector and an infectee and is an important parameter which can impact on the estimation of the reproduction number. Whilst several parameters influencing infection transmission are expected to be consistent across populations, the serial interval can vary across and within populations over time. Therefore, local estimates are preferable for use in epidemiological models developed at a regional level. We used data collected as part of the national contact tracing process in Ireland to estimate the serial interval of SARS-CoV-2 infection in the Irish population, and to estimate the proportion of transmission events that occurred prior to the onset of symptoms. RESULTS: After data cleaning, the final dataset consisted of 471 infected close contacts from 471 primary cases. The median serial interval was 4 days, mean serial interval was 4.0 (95% confidence intervals 3.7, 4.3) days, whilst the 25th and 75th percentiles were 2 and 6 days respectively. We found that intervals were lower when the primary or secondary case were in the older age cohort (greater than 64 years). Simulating from an incubation period distribution from international literature, we estimated that 67% of transmission events had greater than 50% probability of occurring prior to the onset of symptoms in the infector. CONCLUSIONS: Whilst our analysis was based on a large sample size, data were collected for the primary purpose of interrupting transmission chains. Similar to other studies estimating the serial interval, our analysis is restricted to transmission pairs where the infector is known with some degree of certainty. Such pairs may represent more intense contacts with infected individuals than might occur in the overall population. It is therefore possible that our analysis is biased towards shorter serial intervals than the overall population.


Subject(s)
COVID-19 , Contact Tracing , Aged , Humans , Ireland/epidemiology , SARS-CoV-2 , Time Factors
13.
Epidemiol Infect ; 149: e157, 2021 04 27.
Article in English | MEDLINE | ID: covidwho-1203374

ABSTRACT

Hospital healthcare workers (HCWs) are at increased risk of contracting COVID-19 infection. We aimed to determine the seroprevalence of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) antibodies in HCWs in Ireland. Two tertiary referral hospitals in Irish cities with diverging community incidence and seroprevalence were identified; COVID-19 had been diagnosed in 10.2% and 1.8% of staff respectively by the time of the study (October 2020). All staff of both hospitals (N = 9038) were invited to participate in an online questionnaire and blood sampling for SARS-CoV-2 antibody testing. Frequencies and percentages for positive SARS-CoV-2 antibody were calculated and adjusted relative risks (aRR) for participant characteristics were calculated using multivariable regression analysis. In total, 5788 HCWs participated (64% response rate). Seroprevalence of antibodies to SARS-CoV-2 was 15% and 4.1% in hospitals 1 and 2, respectively. Thirty-nine percent of infections were previously undiagnosed. Risk for seropositivity was higher for healthcare assistants (aRR 2.0, 95% confidence interval (CI) 1.4-3.0), nurses (aRR: 1.6, 95% CI 1.1-2.2), daily exposure to patients with COVID-19 (aRR: 1.6, 95% CI 1.2-2.1), age 18-29 years (aRR: 1.4, 95% CI 1.1-1.9), living with other HCWs (aRR: 1.3, 95% CI 1.1-1.5), Asian background (aRR: 1.3, 95% CI 1.0-1.6) and male sex (aRR: 1.2, 95% CI 1.0-1.4). The HCW seroprevalence was six times higher than community seroprevalence. Risk was higher for those with close patient contact. The proportion of undiagnosed infections call for robust infection control guidance, easy access to testing and consideration of screening in asymptomatic HCWs. With emerging evidence of reduction in transmission from vaccinated individuals, the authors strongly endorse rapid vaccination of all HCWs.


Subject(s)
Antibodies, Viral/blood , COVID-19 , Personnel, Hospital/statistics & numerical data , Adolescent , Adult , Aged , COVID-19/epidemiology , COVID-19/immunology , Cross-Sectional Studies , Female , Humans , Ireland/epidemiology , Male , Middle Aged , SARS-CoV-2/immunology , Seroepidemiologic Studies , Young Adult
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