scholarly journals Vaccine effectiveness against SARS‐CoV‐2 transmission to household contacts during dominance of Delta variant (B.1.617.2), August‐September 2021, the Netherlands

2021 ◽  
Author(s):  
Brechje de Gier ◽  
Stijn Andeweg ◽  
Jantien A. Backer ◽  
Susan J.M. Hahné ◽  
Susan van den Hof ◽  
...  
Keyword(s):  
The Netherlands ◽  
Confidence Interval ◽  
Vaccine Effectiveness ◽  
Contact Tracing ◽  
Household Contacts ◽  
Household Members ◽  
Alpha Variant ◽  
Index Cases

We estimated vaccine effectiveness against onward transmission by comparing secondary attack rates among household members between vaccinated and unvaccinated index cases, based on source and contact tracing data collected when Delta variant was dominant. Effectiveness of full vaccination of the index against transmission to fully vaccinated household contacts was 40% (95% confidence interval (CI) 20‐54%), which is in addition to the direct protection of vaccination of contacts against infection. Effectiveness of full vaccination of the index against transmission to unvaccinated household contacts was 63% (95%CI 46‐75%). We previously reported effectiveness of 73% (95%CI 65‐79%) against transmission to unvaccinated household contacts for the Alpha variant.

scholarly journals Vaccine effectiveness against SARS-CoV-2 transmission to household contacts during dominance of Delta variant (B.1.617.2), the Netherlands, August to September 2021

2021 ◽  
Vol 26 (44) ◽  
Author(s):  
Brechje de Gier ◽  
Stijn Andeweg ◽  
Jantien A Backer ◽  
Susan JM Hahné ◽  
Susan van den Hof ◽  
...  
Keyword(s):  
The Netherlands ◽  
Confidence Interval ◽  
Index Case ◽  
Vaccine Effectiveness ◽  
Contact Tracing ◽  
Household Contacts ◽  
Household Members ◽  
Index Cases

We estimated SARS-CoV-2 vaccine effectiveness against onward transmission by comparing secondary attack rates among household members for vaccinated and unvaccinated index cases, based on source and contact tracing data collected when the Delta variant was dominant. Effectiveness of full vaccination of the index case against transmission to unvaccinated and fully vaccinated household contacts, respectively, was 63% (95% confidence interval (CI): 46–75) and 40% (95% CI: 20–54), in addition to the direct protection of vaccination of contacts against infection.

scholarly journals Vaccine effectiveness against SARS-CoV-2 transmission and infections among household and other close contacts of confirmed cases, the Netherlands, February to May 2021

2021 ◽  
Vol 26 (31) ◽  
Author(s):  
Brechje de Gier ◽  
Stijn Andeweg ◽  
Rosa Joosten ◽  
Ronald ter Schegget ◽  
Naomi Smorenburg ◽  
...  
Keyword(s):  
The Netherlands ◽  
Confidence Interval ◽  
Attack Rate ◽  
Severe Disease ◽  
Vaccine Effectiveness ◽  
Monitoring Data ◽  
High Effectiveness ◽  
Household Contacts ◽  
Index Cases ◽  
Close Contacts

Several studies report high effectiveness of COVID-19 vaccines against SARS-CoV-2 infection and severe disease, however an important knowledge gap is the vaccine effectiveness against transmission (VET). We present estimates of the VET to household and other close contacts in the Netherlands, from February to May 2021, using contact monitoring data. The secondary attack rate among household contacts was lower for fully vaccinated than unvaccinated index cases (11% vs 31%), with an adjusted VET of 71% (95% confidence interval: 63–77).

scholarly journals Yield of Systematic Longitudinal Screening of Household Contacts of Pre-Extensively Drug Resistant (PreXDR) and Extensively Drug Resistant (XDR) Tuberculosis Patients in Mumbai, India

2020 ◽  
Vol 5 (2) ◽  
pp. 83
Author(s):  
Roma Haresh Paryani ◽  
Vivek Gupta ◽  
Pramila Singh ◽  
Madhur Verma ◽  
Sabira Sheikh ◽  
...  
Keyword(s):  
Contact Tracing ◽  
Drug Resistant ◽  
Household Contacts ◽  
Tb Treatment ◽  
Extensively Drug Resistant ◽  
High Incidence ◽  
Resistance Patterns ◽  
One Year ◽  
Index Cases

While risk of tuberculosis (TB) is high among household contacts (HHCs) of pre-extensively drug resistant (pre-XDR) TB and XDR-TB, data on yield of systematic longitudinal screening are lacking. We aim to describe the yield of systematic longitudinal TB contact tracing among HHCs of patients with pre-XDR-TB and XDR-TB. At the Médecins Sans Frontières (MSF) clinic, Mumbai, India a cohort comprising 518 HHCs of 109 pre-XDR and XDR index cases was enrolled between January 2016 and June 2018. Regular HHC follow-ups were done till one year post treatment of index cases. Of 518 HHCs, 23 had TB (21 on TB treatment and two newly diagnosed) at the time of first visit. Of the rest, 19% HHCs had no follow-ups. Fourteen (3.5%) TB cases were identified among 400 HHCs; incidence rate: 2072/100,000 person-years (95% CI: 1227–3499). The overall yield of household contact tracing was 3% (16/518). Of 14 who were diagnosed with TB during follow-up, six had drug susceptible TB (DSTB); six had pre-XDR-TB and one had XDR-TB. Five of fourteen cases had resistance patterns concordant with their index case. In view of the high incidence of TB among HHCs of pre-XDR and XDR-TB cases, follow-up of HHCs for at least the duration of index cases’ treatment should be considered.

scholarly journals Role of children in household transmission of COVID-19

2020 ◽  
pp. archdischild-2020-319910 ◽  
Author(s):  
Jieun Kim ◽  
Young June Choe ◽  
Jin Lee ◽  
Young Joon Park ◽  
Ok Park ◽  
...  
Keyword(s):  
Attack Rate ◽  
Index Case ◽  
Clinical Findings ◽  
International Travel ◽  
Contact Tracing ◽  
Secondary Case ◽  
Household Transmission ◽  
Household Members ◽  
Index Cases

ObjectiveTransmissibility of COVID-19 by children in the household is not clear. Herein, we describe children’s role in household transmission of COVID-19.Design and settingAll paediatric COVID-19 index cases and their household members reported from 20 January to 6 April 2020 in South Korea were reviewed. The secondary attack rate (SAR) from child index case to household secondary case was calculated. Epidemiological and clinical findings of child index case-household secondary case pair was assessed.ResultsA total of 107 paediatric COVID-19 index cases and 248 of their household members were identified. One pair of paediatric index-secondary household case was identified, giving a household SAR of 0.5% (95% CI 0.0% to 2.6%). The index case was self-quarantined at home after international travel, stayed in her room, but shared a meal table with the secondary case.ConclusionThe SAR from children to household members was low in the setting of social distancing, underscoring the importance of rigorous contact tracing and early isolation in limiting transmission within households.

scholarly journals Effect of vaccination on transmission of COVID-19: an observational study in healthcare workers and their households

2021 ◽  
Author(s):  
Anoop Shah ◽  
Ciara Gribben ◽  
Jennifer Bishop ◽  
Peter Hanlon ◽  
David Caldwell ◽  
...  
Keyword(s):  
Confidence Interval ◽  
Health Care Workers ◽  
Record Linkage ◽  
Lower Risk ◽  
Healthcare Workers ◽  
Substantial Reduction ◽  
Linkage Study ◽  
Household Contacts ◽  
Care Workers ◽  
Household Members

Background: The effect of vaccination for COVID-19 on onward transmission is unknown. Methods: A national record linkage study determined documented COVID-19 cases and hospitalizations in unvaccinated household members of vaccinated and unvaccinated healthcare workers from 8th December 2020 to 3rd March 2021. The primary endpoint was COVID-19 >= 14 days following the first dose. Results: The cohort comprised of 194,362 household members (mean age 31.1 years) and 144,525 healthcare workers (mean age 44.4 years). 113,253 (78.3%) of healthcare workers received at least one dose of the BNT162b2 mRNA or ChAdOx1 nCoV-19 vaccine and 36,227 (25.1%) received a second dose. Household members of vaccinated healthcare workers had a lower risk of COVID-19 case compared to household members of unvaccinated healthcare worker (rate per 100 person-years 9.40 versus 5.93; HR 0.70, 95% confidence interval [CI] 0.63-0.78). The effect size for COVID-19 hospitalization was similar, with the confidence interval crossing the null (HR 0.77 [0.53-1.10]). The rate per 100 person years was lower in vaccinated compared to unvaccinated healthcare workers for documented (20.13 versus 8.51; HR 0.45 [0.42-0.49]) and hospitalized COVID-19 (0.97 versus 0.14; HR 0.16 [0.09-0.27]). Compared to the period before the first dose, the risk of documented COVID-19 case was lower at >= 14 days after the second dose for household members (HR 0.46 [0.30-0.70]) and healthcare workers (HR 0.08 [0.04-0.17]). Conclusion: Vaccination of health care workers was associated with a substantial reduction in COVID-19 cases in household contacts consistent with an effect of vaccination on transmission.

scholarly journals Transmission and serotype features of hand foot mouth disease in household contacts in Dong Thap, Vietnam

2019 ◽  
Vol 19 (1) ◽  
Author(s):  
Cuong Quoc Hoang ◽  
Thao Thanh Thi Nguyen ◽  
Nguyen Xuan Ho ◽  
Hai Duc Nguyen ◽  
An Binh Nguyen ◽  
...  
Keyword(s):  
Attack Rate ◽  
Neutralizing Antibodies ◽  
Index Case ◽  
Fold Increase ◽  
Mouth Disease ◽  
Rt Pcr ◽  
Household Contacts ◽  
Two Samples ◽  
Household Members ◽  
Index Cases

Abstract Background Hand, foot and mouth disease (HFMD) has emerged as a major public health issue in Vietnam since 2003. We aimed to investigate the household transmission of HFMD and its causative viruses from 150 households in a high incidence province in Vietnam. Methods A longitudinal study was conducted in patients presenting to the provincial hospital with a HFMD-like syndrome, along with their household members between April and August 2014 in Dong Thap Province. Each participant was followed up for 2 weeks. We enrolled 150 patients aged under 15 who were clinically diagnosed with HFMD in Dong Thap Hospital, 600 household members, and 581/600 household members completed the study. All participants were interviewed using a standard questionnaire. Throat swabs and blood samples were taken for molecular detection of viruses and assessment of neutralizing antibodies, respectively. Index cases were defined using a clinical case definition, household contact cases were defined using a similar definition applied to the 2 weeks before admission and 2 weeks after discharge of the index case. Characteristics of index cases, household contacts, the attack rate, serotype features and related factors of HFMD were reported. Result Among 150 index cases, 113 were laboratory confirmed: 90/150 were RT-PCR-positive, 101/142 had a ≥ 4-fold increase of neutralizing antibody against Enterovirus A71 (EV-A71), Coxsackievirus (CV) A6 or CV-A16 across the two samples collected. 80/150 (53%) were males, and 45/150 (30%) were under the age of 1. The predominant serotype was CV-A6, identified in 57/87 (65.5%) of the specimens. No deaths were reported. Among 581 household contacts, 148 were laboratory confirmed: 12/581 were RT-PCR-positive, 142/545 had a ≥ 4-fold increase of neutralizing antibodies against EV-A71, CV-A6 or CV-A16; 4 cases experienced HFMD in the past 4 weeks. Attack rate among household contacts was 148/581 (25.5%). In 7/12 (58%) instances, the index and secondary cases were infected with the same serotype. Having a relationship to index case was significantly associated with EV infection. Conclusion The attack rate among household contacts was relatively high (25.5%) in this study and it seems justified to also consider the household setting as an additional target for intervention programs.

scholarly journals Characteristics of Household Transmission of COVID-19

2020 ◽  
Vol 71 (8) ◽  
pp. 1943-1946 ◽  
Author(s):  
Wei Li ◽  
Bo Zhang ◽  
Jianhua Lu ◽  
Shihua Liu ◽  
Zhiqiang Chang ◽  
...  
Keyword(s):  
Risk Factors ◽  
Attack Rate ◽  
Rt Pcr ◽  
Spousal Relationship ◽  
Telephone Interviews ◽  
Household Contacts ◽  
Household Transmission ◽  
Household Members ◽  
Baseline Characteristics ◽  
Index Cases

Abstract Background Since December 2019, SARS-CoV-2 has extended to most parts of China with >80 000 cases and to at least 100 countries with >60 000 international cases as of 15 March 2020. Here we used a household cohort study to determine the features of household transmission of COVID-19. Methods A total of 105 index patients and 392 household contacts were enrolled. Both index patients and household members were tested by SARS-CoV-2 RT-PCR. Information on all recruited individuals was extracted from medical records and confirmed or supplemented by telephone interviews. The baseline characteristics of index cases and contact patients were described. Secondary attack rates of SARS-CoV-2 to contact members were computed and the risk factors for transmission within the household were estimated. Results Secondary transmission of SARS-CoV-2 developed in 64 of 392 household contacts (16.3%). The secondary attack rate to children was 4% compared with 17.1% for adults. The secondary attack rate to the contacts within the households with index patients quarantined by themselves since onset of symptoms was 0% compared with 16.9% for contacts without quarantined index patients. The secondary attack rate to contacts who were spouses of index cases was 27.8% compared with 17.3% for other adult members in the households. Conclusions The secondary attack rate of SARS-CoV-2 in household is 16.3%. Age of household contacts and spousal relationship to the index case are risk factors for transmission of SARS-CoV-2 within a household. Quarantine of index patients at home since onset of symptoms is useful to prevent the transmission of SARS-Co-2 within a household.

scholarly journals Increased Transmissibility of the SARS-CoV-2 Alpha Variant in a Japanese Population

2021 ◽  
Vol 18 (15) ◽  
pp. 7752
Author(s):  
Hideo Tanaka ◽  
Atsushi Hirayama ◽  
Hitomi Nagai ◽  
Chika Shirai ◽  
Yuki Takahashi ◽  
...  
Keyword(s):  
Japanese Population ◽  
Error Variance ◽  
Cross Sectional Study ◽  
Cross Sectional ◽  
Fourth Group ◽  
Household Contacts ◽  
The Third ◽  
Before And After ◽  
Alpha Variant ◽  
Index Cases

To assess the relative transmissibility of the SARS-CoV-2 Alpha variant compared to the pre-existing SARS-CoV-2 in Japan, we performed a cross-sectional study to determine the secondary attack rate of COVID-19 in household contacts before and after the Alpha variant became dominant in Osaka. We accessed 290 household contacts whose index cases were diagnosed between 1 and 20 December 2020 (the third epidemic group), at a time when Osaka was free of the Alpha variant. We also accessed 398 household contacts whose index cases were diagnosed between 20 April and 3 May 2021 (the fourth epidemic group), by which time the Alpha variant had become dominant. We identified 124 household contacts whose index case was determined positive for the Alpha variant (Alpha group) in this fourth group. The secondary attack rates in the fourth group (34.7%) and the Alpha group (38.7%) were significantly higher than that in the third group (19.3%, p < 0.001). Multivariable Poisson regression analysis with a robust error variance showed a significant excess risk in the fourth group (1.90, 95% CI = 1.47–2.48) and the Alpha group (2.34, 95% CI = 1.71–3.21). This finding indicates that the SARS-CoV-2 Alpha variant has an approximately 1.9–2.3-fold higher transmissibility than the pre-existing virus in the Japanese population.

scholarly journals Comprehensive Contact Tracing, Testing and Sequencing Show Limited Transmission of SARS-CoV-2 between Children in Schools in Norway, August 2020 to May 2021

2021 ◽  
Vol 9 (12) ◽  
pp. 2587
Author(s):  
Brita Askeland Winje ◽  
Trine Skogset Ofitserova ◽  
Ola Brønstad Brynildsrud ◽  
Margrethe Greve-Isdahl ◽  
Karoline Bragstad ◽  
...  
Keyword(s):  
Mitigation Measures ◽  
Contact Tracing ◽  
Whole Genome ◽  
Viral Strain ◽  
Significant Difference ◽  
Valid Estimate ◽  
Contact Investigations ◽  
Alpha Variant ◽  
Index Cases

The role of children in the spread of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) in schools has been a topic of controversy. In this study among school contacts of SARS-CoV-2 positive children in 43 contact-investigations, we investigated SARS-CoV-2 transmission in Norway, August 2020–May 2021. All participants were tested twice within seven to ten days, using SARS-CoV-2 PCR on home-sampled saliva. Positive samples were whole genome sequenced. Among the 559 child contacts, eight tested positive (1.4%, 95% CI 0.62–2.80), with no significant difference between primary (1.0%, 95% CI 0.27–2.53) and secondary schools (2.6%, 95% CI 0.70–6.39), p = 0.229, nor by viral strain, non-Alpha (1.4%, 95% CI 0.50–2.94) and Alpha variant (B.1.1.7) (1.7%, 95% CI 0.21–5.99), p = 0.665. One adult contact (1/100) tested positive. In 34 index cases, we detected 13 different SARS-CoV-2 Pango lineage variants, with B.1.1.7 being most frequent. In the eight contact-investigations with SARS-CoV-2 positive contacts, four had the same sequence identity as the index, one had no relation, and three were inconclusive. With mitigation measures in place, the spread of SARS-CoV-2 from children in schools is limited. By excluding contact-investigations with adult cases known at the time of enrolment, our data provide a valid estimate on the role of children in the transmission of SARS-CoV-2 in schools.

scholarly journals Epidemiological, virological and serological investigation into a SARS-CoV-2 outbreak (Alpha variant) in a primary school in Geneva, Switzerland: a prospective longitudinal study

2021 ◽  
Author(s):  
Elsa Lorthe ◽  
Mathilde Bellon ◽  
Gregoire Michielin ◽  
Julie Berthelot ◽  
Maria-Eugenia Zaballa ◽  
...  
Keyword(s):  
Primary School ◽  
Contact Tracing ◽  
Teaching Staff ◽  
Serological Tests ◽  
Prospective Longitudinal Study ◽  
School Settings ◽  
Serological Investigation ◽  
Household Members ◽  
Alpha Variant ◽  
Prospective Longitudinal

Background Twenty-one months into the pandemic, the extent to which young children get infected and transmit SARS-CoV-2 in school settings remains controversial, in particular with variants of concern. We report a prospective epidemiological, virological and serological investigation of a SARS-CoV-2 outbreak in a primary school in Geneva, Switzerland, in April-May 2021. Methods This outbreak investigation is part of a longitudinal, prospective, primary school-based surveillance study (SEROCoV-Schools). It involved repeated testing of pupils and teachers and household members of participants who tested positive. Rapid antigen tests and/or real-time reverse transcription polymerase chain reaction were performed at Day 0-2 and Day 5-7; serologies on dried capillary blood samples were performed at Day 0-2 and Day 30. Contact tracing interviews and SARS-CoV-2 whole genome sequencing were carried out for positive cases. Results This SARS-CoV-2 outbreak caused by the Alpha variant involved 20 children aged 4 to 6 years from 4 classes, 2 teachers and 3 household members. Infection attack rates were between 11.8 and 62.0% among pupils from the 4 classes, 22.2% among teachers and 0% among non-teaching staff. Secondary attack rate among household members was 10.7%. Symptoms were reported by 63% of infected children, 100% of teachers and 66.7% of household members. All analysed sequences but one showed 100% identity. Serological tests detected 8 seroconversions unidentified by SARS-CoV-2 virological tests. Conclusions This study confirmed child-to-child and child-to-adult transmission of the infection. SARS-CoV-2 can spread rapidly between children and adults in school settings, and is thereby introduced into households. Effective measures to limit transmission in schools have the potential to reduce the overall community circulation.

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