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 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 High transmissibility of COVID-19 near symptom onset

2020 ◽  
Author(s):  
Hao-Yuan Cheng ◽  
Shu-Wan Jian ◽  
Ding-Ping Liu ◽  
Ta-Chou Ng ◽  
Wan-Ting Huang ◽  
...  
Keyword(s):  
Symptom Onset ◽  
Attack Rate ◽  
Paired Data ◽  
Rapid Reduction ◽  
Social Distancing ◽  
Household Contacts ◽  
Exposure Windows ◽  
Index Cases ◽  
Over Time ◽  
Close Contacts

AbstractBackgroundThe dynamics of coronavirus disease 2019 (COVID-19) transmissibility after symptom onset remains unknown.MethodsWe conducted a prospective case-ascertained study on laboratory-confirmed COVID-19 cases and their contacts. Secondary clinical attack rate (considering symptomatic cases only) was analyzed for different exposure windows after symptom onset of index cases and for different exposure settings.ResultsThirty-two confirmed patients were enrolled and 12 paired data (index-secondary cases) were identified among the 1,043 contacts. The secondary clinical attack rate was 0.9% (95% CI 0.5–1.7%). The attack rate was higher among those whose exposure to index cases started within five days of symptom onset (2.4%, 95% CI 1.1–4.5%) than those who were exposed later (zero case from 605 close contacts, 95% CI 0–0.61%). The attack rate was also higher among household contacts (13.6%, 95% CI 4.7–29.5%) and non- household family contacts (8.5%, 95% CI 2.4–20.3%) than that in healthcare or other settings. The higher secondary clinical attack rate for contacts near symptom onset remained when the analysis was restricted to household and family contacts. There was a trend of increasing attack rate with the age of contacts (p for trend < 0.001).ConclusionsHigh transmissibility of COVID-19 near symptom onset suggests that finding and isolating symptomatic patients alone may not suffice to contain the epidemic, and more generalized social distancing measures are required. Rapid reduction of transmissibility over time implies that prolonged hospitalization of mild cases might not be necessary in large epidemics.

scholarly journals A meta-analysis on the role of children in SARS-CoV-2 in household transmission clusters

2020 ◽  
Author(s):  
Yanshan Zhu ◽  
Conor J Bloxham ◽  
Katina D Hulme ◽  
Jane E Sinclair ◽  
Zhen Wei Marcus Tong ◽  
...  
Keyword(s):  
Confidence Interval ◽  
Risk Ratio ◽  
Attack Rate ◽  
Index Case ◽  
Meta Analysis ◽  
Household Contacts ◽  
Household Transmission ◽  
Potential Vaccine ◽  
Index Cases

Abstract The role of children in the spread of SARS-CoV-2 remains highly controversial. To address this issue, we performed a meta-analysis of the published literature on household SARS-CoV-2 transmission clusters (n=213 from 12 countries). Only 8 (3.8%) transmission clusters were identified as having a paediatric index case. Asymptomatic index cases were associated with a lower secondary attack in contacts than symptomatic index cases (estimate risk ratio [RR], 0.17; 95% confidence interval [CI], 0.09-0.29). To determine the susceptibility of children to household infections the secondary attack rate (SAR) in paediatric household contacts was assessed. The secondary attack rate in paediatric household contacts was lower than in adult household contacts (RR, 0.62; 95% CI, 0.42-0.91). These data have important implications for the ongoing management of the COVID-19 pandemic, including potential vaccine prioritization strategies.

scholarly journals A meta-analysis on the role of children in SARS-CoV-2 in household transmission clusters

2020 ◽  
Author(s):  
Yanshan Zhu ◽  
Conor J. Bloxham ◽  
Katina D. Hulme ◽  
Jane E. Sinclair ◽  
Zhen Wei Marcus Tong ◽  
...  
Keyword(s):  
Confidence Interval ◽  
Family Member ◽  
Attack Rate ◽  
Index Case ◽  
Meta Analysis ◽  
Household Contacts ◽  
Household Transmission ◽  
Potential Vaccine ◽  
Index Cases

ABSTRACTThe role of children in the spread of SARS-CoV-2 remains highly controversial. To address this issue, we performed a meta-analysis of the published literature on household SARS-CoV-2 transmission clusters (n=213 from 12 countries). Only 8 (3.8%) transmission clusters were identified as having a paediatric index case. Asymptomatic index cases were associated with a lower secondary attack in contacts than symptomatic index cases (estimate risk ratio [RR], 0.17; 95% confidence interval [CI], 0.09-0.29). To determine the susceptibility of children to household infections the secondary attack rate (SAR) in paediatric household contacts was assessed. The secondary attack rate in paediatric household contacts was lower than in adult household contacts (RR, 0.62; 95% CI, 0.42-0.91). These data have important implications for the ongoing management of the COVID-19 pandemic, including potential vaccine prioritization strategies.40-word summaryIn household transmission clusters of SARS-CoV-2 children are unlikely to be the index case. Children are also less likely than adults to be infected with SARS-CoV-2 from a family member.

scholarly journals Epidemiology and contact tracing assessment of COVID-19 and potential risk of transmission at different exposure settings: A prospective cohort study

2021 ◽  
Author(s):  
Abu Shadat M Noman ◽  
Mohammed Rezaul Karim ◽  
ASM Zahed ◽  
ATM Rezaul Karim ◽  
Syed S Islam
Keyword(s):  
Risk Ratio ◽  
Attack Rate ◽  
Close Contact ◽  
Household Contact ◽  
Control Measures ◽  
Effective Control ◽  
Secondary Contact ◽  
Epidemiological Characteristics ◽  
Index Cases ◽  
Close Contacts

Abstract Background: Transmission risk of coronavirus disease 2019 (COVID-19) to close contacts and at different exposure settings are yet to be fully understood for the evaluation of effective control measures. Methods: We traced 1171 close contact cases who were linked to 291 index cases between July 3, 2020 and September 3, 2020. Clinical and epidemiological characteristics of all index cases, close contacts, and secondary contact cases were collected and analyzed the secondary attack rate and risk of transmission at different exposure settings. Results: Median age of 291 index cases were 43.0 years (range 18.5-82.3) including 213 male and 78 females. Among all 1171 close contact cases, 39(3.3%) cases were identified as secondary infected cases. Among 39 secondary cases, 33(84.62%) cases were symptomatic and 3 (7.69%) cases were asymptomatic. Of the 33 symptomatic cases, 31(86.1%) male and 5(13.9%) female. Of these 36 symptomatic cases, 24(66.7%) cases between age 20-59 and remaining 12(33.3%) cases were age 60 and over. Of the 36 symptomatic cases, 11(30.6%) cases were identified as severe, 19(52.8%) as moderate and 6(16.7%) as mild. The overall secondary clinical attack rate was 3.07% (95% CI 2.49-3.64). The attack rate was higher among those aged between 50 to 69 years and shows higher risk of transmission than age below 50 years. The attack rate was higher among household contact (6.17%(95%CI 4.7-7.6; risk ratio 2.44[95%CI1.5-3.4]), and lower in hospital facility (2.29%,95%CI0.58-3.40; [risk ratio 0.91,95%CI 0.17-1.9]), funeral ceremony (2.53%,95%CI 0.32-4.73), work places (3.95%,95% CI2.5-5.42 [risk ratio 1.56,95%CI 0.63-2.5]), family contacts (3.87%,95%CI 2.4-5.3; risk ratio 1.53,95%CI 0.61-2.45]). Conclusions: Among all exposure settings analyzed, household contact exposure setting remained the highest transmission probability and risk of transmission of COVID-19 with the increase of age and disease severity.

scholarly journals Transmission of SARS-CoV-2 from Children and Adolescents

2020 ◽  
Author(s):  
Victoria T. Chu ◽  
Anna R. Yousaf ◽  
Karen Chang ◽  
Noah G. Schwartz ◽  
Clinton J. McDaniel ◽  
...  
Keyword(s):  
Public Health ◽  
Cohort Study ◽  
Confidence Interval ◽  
Children And Adolescents ◽  
Retrospective Cohort Study ◽  
Attack Rate ◽  
Retrospective Cohort ◽  
Mitigation Strategies ◽  
Household Contacts ◽  
Council Of State

AbstractA better understanding of SARS-CoV-2 transmission from children and adolescents is crucial for informing public health mitigation strategies. We conducted a retrospective cohort study among household contacts of primary cases defined as children and adolescents aged 7⍰19 years with laboratory evidence of SARS-CoV-2 infection acquired during an overnight camp outbreak. Among household contacts, we defined secondary cases using the Council of State and Territorial Epidemiologists definition. Among 526 household contacts of 224 primary cases, 48 secondary cases were identified, corresponding to a secondary attack rate of 9% (95% confidence interval [CI], 7%–12%). Our findings show that children and adolescents can transmit SARS-CoV-2 to adult contacts and other children in a household setting.

scholarly journals A comparison of COVID-19 secondary attack rate in household and close contacts compared to current risk stratification guidelines of the Kerala government

2021 ◽  
pp. 004947552110020
Author(s):  
Balram Rathish ◽  
Arun Wilson ◽  
Sonya Joy
Keyword(s):  
High Risk ◽  
Risk Stratification ◽  
Attack Rate ◽  
Low Risk ◽  
Contact Tracing ◽  
Index Cases ◽  
Current Risk ◽  
Close Contacts

COVID-19 has been found to be highly infectious with a high secondary attack rate with a R0 of 3.3. However, the secondary attack rate based on risk stratification is sparsely reported, if ever. We studied the contact tracing data for two index cases of COVID-19 with some overlap of contacts. We found that 60% of high-risk contacts and 0% of low-risk contacts of symptomatic COVID-19 patients contracted the infection, in keeping with the Kerala government contact risk stratification guidelines.

scholarly journals Comparative Household Secondary Attack Rates associated with B.1.1.7, B.1.351, and P.1 SARS-CoV-2 Variants

2021 ◽  
Author(s):  
Kevin A Brown ◽  
Semra Tibebu ◽  
Nick Daneman ◽  
Kevin L Schwartz ◽  
Michael Whelan ◽  
...  
Keyword(s):  
Symptom Onset ◽  
Attack Rate ◽  
Surveillance System ◽  
Disease Surveillance ◽  
Index Case ◽  
Wild Type ◽  
Vaccination Rates ◽  
Household Contacts ◽  
Disease Surveillance System ◽  
Index Cases

Background: The emergence of SARS-CoV-2 variants associated with increased transmissibility are driving a 3rd global surge in COVID-19 incidence. There are currently few reliable estimates for the P.1 and B.1.351 lineages. We sought to compare the secondary attack rates of SARS-COV-2 mutations and variants in Canada's largest province of Ontario, using a previously validated household-based approach. Methods: We identified individuals with confirmed SARS-CoV-2 infection in Ontario's provincial reportable disease surveillance system. Cases were grouped into households based on reported residential address. Index cases had the earliest of symptom onset in the household. Household secondary attack rate was defined as the percentage of household contacts identified as secondary cases within 1-14 days after the index case. Results: We identified 26,888 index household cases during the study period. Among these, 7,555 (28%) were wild-type, 17,058 (63%) were B.1.1.7, 1674 (6%) were B.1.351 or P.1, and 601 (2%) were non-VOC mutants (Table 1). The secondary attack rates, according to index case variant were as follows: 20.2% (wild-type), 25.1% (B.1.1.7), 27.2% (B.1.351 or P.1), and 23.3% (non-VOC mutants). In adjusted analyses, we found that B.1.1.7, B.1.351, and P.1 index cases had the highest transmissibility (presumptive B.1.1.7 OR adjusted=1.49, 95%CI 1.36, 1.64; presumptive B.1.351 or P.1 OR adjusted=1.60, 95%CI 1.37, 1.87). Discussion: Substantially higher transmissibility associated with variants will make control of SARS-CoV-2 more difficult, reinforcing the urgent need to increase vaccination rates globally.

scholarly journals High Rate of SARS-CoV-2 Transmission due to Choir Practice in France at the Beginning of the COVID-19 Pandemic

2020 ◽  
Author(s):  
Nathalie CHARLOTTE
Keyword(s):  
Attack Rate ◽  
Transmission Rate ◽  
High Rate ◽  
Individual Risk ◽  
High Transmission ◽  
The Mean ◽  
The Individual ◽  
Practice Methods ◽  
Index Cases ◽  
Close Contacts

Background: There has been little focus on the individual risk of acquiring COVID-19 related to choir practice. Methods: We report the case of a high transmission rate of SARS-CoV-2 linked to an indoor choir rehearsal in France in March 2020 at the beginning of the COVID-19 pandemic. Results: A total of 27 participants, including 25 male singers, a conductor and an accompanist attended a choir practice on March 12, 2020. The practice was indoor and took place in a non-ventilated space of 45 m2. No choir member reported having been symptomatic for COVID-19 between March 2 and March 12.The mean age of the participants was 66.9 (range 35-86) years. 70% of the participants (19 of 27) were diagnosed with COVID-19 from 1 to 12 days after the rehearsal with a median of 5.1 days. 36% of the cases needed a hospitalization (7/19), and 21% (4/19) were admitted to an ICU. The index cases were possibly multiple. Discussion: The choir practice was planned in March 2020 at a period when the number of new cases of COVID-19 began to grow exponentially in France because SARS-CoV-2 was actively circulating. The secondary attack rate (70%) was much higher than it is described within households (10-20%) and among close contacts made outside households (0-5%). Singing might have contributed to enhance SARS-CoV-2 person-to-person transmission through emission of droplets and aerosolization in a closed non ventilated space with a relative high number of people including multiple pre-symptomatic suspected index cases. Conclusion: Indoor choir practice should be suspended during SARS-CoV-2 outbreaks. Further studies are necessary to test the spread of the virus by the act of singing. As the benefits of the barrier measures and social distancing are known to be effective in terms of a reduction in the incidence of the COVID-19, experts recommendations concerning the resuming of choir practice are necessary.

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