Sensitivity of infectious SARS-CoV-2 B.1.1.7 and B.1.351 variants to neutralizing antibodies.

Severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) B.1.1.7 and B.1.351 variants were first identified in the United Kingdom and South Africa, respectively, and have since spread to many countries. These variants harboring diverse mutations in the gene encoding the spike protein raise important concerns about their immune evasion potential. Here, we isolated infectious B.1.1.7 and B.1.351 strains from acutely infected individuals. We examined sensitivity of the two variants to SARS-CoV-2 antibodies present in sera and nasal swabs from individuals infected with previously circulating strains or who were recently vaccinated, in comparison with a D614G reference virus. We utilized a new rapid neutralization assay, based on reporter cells that become positive for GFP after overnight infection. Sera from 58 convalescent individuals collected up to 9 months after symptoms, similarly neutralized B.1.1.7 and D614G. In contrast, after 9 months, convalescent sera had a mean sixfold reduction in neutralizing titers, and 40% of the samples lacked any activity against B.1.351. Sera from 19 individuals vaccinated twice with Pfizer Cominarty, longitudinally tested up to 6 weeks after vaccination, were similarly potent against B.1.1.7 but less efficacious against B.1.351, when compared to D614G. Neutralizing titers increased after the second vaccine dose, but remained 14-fold lower against B.1.351. In contrast, sera from convalescent or vaccinated individuals similarly bound the three spike proteins in a flow cytometry-based serological assay. Neutralizing antibodies were rarely detected in nasal swabs from vaccinees. Thus, faster-spreading SARS-CoV-2 variants acquired a partial resistance to neutralizing antibodies generated by natural infection or vaccination, which was most frequently detected in individuals with low antibody levels. Our results indicate that B1.351, but not B.1.1.7, may increase the risk of infection in immunized individuals.

Systematic Severe Acute Respiratory Syndrome Coronavirus 2 Screening at Hospital Admission in Children: A French Prospective Multicenter Study.

To assess the relevance of systematic severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) screening of all children admitted to hospital, we conducted a prospective multicenter study including 438 consecutive hospitalized children. A symptom-based SARS-CoV-2 testing strategy failed to identify 45% (95% confidence interval, 24%-68%) of hospitalized children infected by SARS-CoV-2. To limit intrahospital transmission, a systematic screening of children admitted to hospital should be considered.

Assessment of SARS-CoV-2 infection by Reverse transcription-PCR and serology in the Paris area: a cross-sectional study.

BACKGROUND: Several studies indicated that children seem to be less frequently infected with SARS-CoV-2 and are potentially less contagious than adults. To examine the spread of SARS-CoV-2, we combined both Reverse transcription-PCR testing and serology in children in the most affected region in France, Paris, during the COVID-19 epidemic. METHODS: From 14 April 2020 to 12 May 2020, we conducted a cross-sectional, prospective, multicentre study. Healthy controls and pauci-symptomatic children from birth to age 15 years were enrolled by 27 ambulatory paediatricians. A nasopharyngeal swab was taken for detection of SARS-CoV-2 by Reverse transcription-PCR and a microsample of blood for micromethod serology. RESULTS: Among the 605 children, 322 (53.2%) were asymptomatic and 283 (46.8%) were symptomatic. Reverse transcription-PCR and serology results were positive for 11 (1.8%) and 65 (10.7%) children, respectively, with no significant difference between asymptomatic and pauci-symptomatic children. Only three children were Reverse transcription-PCR-positive without any antibody response detected. The frequency of Reverse transcription-PCR SARS-CoV-2 positivity was significantly higher for children with positive than negative serology results (12.3% vs 0.6%, p<0.001). Contact with a person with confirmed COVID-19 increased the odds of Reverse transcription-PCR positivity (OR 7.8, 95% CI 1.5 to 40.7) and serology positivity (OR 15.1, 95% CI 6.6 to 34.6). CONCLUSION: In an area heavily affected by COVID-19, after the peak of the first epidemic wave and during the lockdown, the rate of children with Reverse transcription-PCR SARS-CoV-2 positivity was very low (1.8%), but that of serology positivity was higher (10.7%). Most children with positive Reverse transcription-PCR results also had positive serology results. TRIAL REGISTRATION NUMBER: NCT04318431.