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EuropePMC; 2021.
Preprint in English | EuropePMC | ID: ppcovidwho-321615


Background: The SARS-CoV-2 Delta variant is highly transmissible and spreading globally but a detailed understanding of community transmission risks in highly vaccinated populations is lacking.Methods: Between September 2020 and August 2021, we recruited 510 community contacts of 422 UK COVID-19 cases to a cohort study. A total of 7194 upper respiratory tract (URT) samples were tested from sequential daily sampling of participants for up to 20 days. We analysed transmission risk by vaccination status for 139 contacts exposed to the Delta variant. We compared viral load (VL) trajectories from fully-vaccinated cases of Delta infection (n=19) with unvaccinated Delta (n=10), Alpha (n=39) and pre-Alpha (n=49) infections.Findings: The household secondary attack rate for fully-vaccinated contacts exposed to Delta was 19.7% (95%CI:11.6-31.3%), compared with 35.7% (95%CI:16.4-61.2%) in the unvaccinated. One third of infections in Delta-exposed contacts arose from fully-vaccinated index cases and one half of infected contacts were also fully-vaccinated. Seven transmission events between fully vaccinated index-contact pairs occurred. Genomic analysis confirmed transmission pathways between fully-vaccinated individuals within three households. Peak VL was similar in vaccinated and unvaccinated individuals with Delta variant infection but vaccinated Delta cases saw significantly faster VL decline than unvaccinated Alpha or Delta cases. Within infected individuals, faster VL growth was correlated with higher peak VL and slower decline.Interpretation: Although vaccination reduces the risk of Delta infection and causes some changes to viral kinetics, fully-vaccinated individuals with breakthrough infections have peak URT VL similar to unvaccinated cases and can efficiently transmit infection in household settings, including to fully vaccinated contacts.Funding: National Institute for Health Research (Award:NIHR200927)Declaration of Interest: The authors declare no relevant conflicts.Ethical Approval: The study was approved by the Health Research Authority (Research Ethics Committee reference: 20/NW/0231).

Euro Surveill ; 26(5)2021 02.
Article in English | MEDLINE | ID: covidwho-1067625


Two London care homes experienced a second COVID-19 outbreak, with 29/209 (13.9%) SARS-CoV-2 RT-PCR-positive cases (16/103 residents, 13/106 staff). In those with prior SARS-CoV-2 exposure, 1/88 (1.1%) individuals (antibody positive: 87; RT-PCR-positive: 1) became PCR-positive compared with 22/73 (30.1%) with confirmed seronegative status. After four months protection offered by prior infection against re-infection was 96.2% (95% confidence interval (CI): 72.7-99.5%) using risk ratios from comparison of proportions and 96.1% (95% CI: 78.8-99.3%) using a penalised logistic regression model.

Antibodies, Viral/blood , COVID-19/prevention & control , Disease Outbreaks/prevention & control , Nursing Homes/statistics & numerical data , Reinfection/prevention & control , SARS-CoV-2/genetics , Adult , Aged , Aged, 80 and over , COVID-19/blood , COVID-19/immunology , COVID-19 Serological Testing , Female , Humans , London , Male , Middle Aged , Pandemics , Reverse Transcriptase Polymerase Chain Reaction , SARS-CoV-2/isolation & purification , Whole Genome Sequencing
Pediatr Infect Dis J ; 39(9): e257-e260, 2020 09.
Article in English | MEDLINE | ID: covidwho-643742


BACKGROUND: To date, although neonatal infections with severe acute respiratory syndrome coronovirus 2 (SARS-CoV-2) have been described, none of these have been proven to be the result of vertical transmission of SARS-CoV-2. METHODS: We describe the probable vertical transmission of SARS-CoV-2 in a neonate born to a mother with coronavirus disease 2019 (COVID-19). RESULTS: Following cesarean section, the neonate was kept in strict isolation. Molecular tests for SARS-CoV-2 on respiratory samples, blood, and meconium were initially negative, but positive on a nasopharyngeal aspirate on the third day of life. On day 5, the neonate developed fever and coryza, which spontaneously resolved. Viral genomic analysis from the mother and neonate showed identical sequences except for 1 nucleotide. CONCLUSION: This report has important implications for infection control and clinical management of pregnant women with COVID-19 and their newborns.

Betacoronavirus/pathogenicity , Coronavirus Infections/transmission , Infectious Disease Transmission, Vertical , Pneumonia, Viral/transmission , Pregnancy Complications, Infectious/virology , Adult , COVID-19 , Cesarean Section , Coronavirus Infections/virology , Female , Humans , Infant, Newborn , Pandemics , Pneumonia, Viral/virology , Pregnancy , SARS-CoV-2