Those variants were associated with an increase in transmissibility and in particular the S: E484K substitution was associated with a compromise in the neutralization by monoclonal antibodies rendering this change of therapeutic concern. 109 specimens that were used for further genome analysis, 68 (62.4%) were from TRIB3 symptomatic infections, 11 (10.1%) were admitted for COVID-19, and 2 (1.8%) required ICU admission with no associated mortality. The predominant computer virus variant was the alpha (B.1.1.7), however a significant association between lineage B.1.526 and amino acid change S: E484K with positives after vaccination was noted when genomes were compared to a large control cohort from a matched time frame. A significant reduction of the HDAC8-IN-1 recovery of infectious computer virus on cell culture as well as delayed time to the first appearance of cytopathic effect was accompanied by an increase in local IgG levels in respiratory samples of vaccinated individuals but upper respiratory tract IgG levels were not different between symptomatic or asymptomatic infections. Conclusions Vaccination reduces the recovery of infectious computer virus in breakthrough infections accompanied by an increase in upper respiratory tract local immune responses. Funding National Institute of Health (The Johns Hopkins Center of Excellence in Influenza Research and Surveillance, HHSN272201400007C), Johns Hopkins University, Maryland Department of Health, Centers for Disease Control and Prevention. Introduction SARS-CoV-2 has caused a devastating pandemic. Millions of global deaths have been recorded with thousands of new cases diagnosed daily, a pattern that significantly changed with the large-scale vaccination in certain countries including the US HDAC8-IN-1 (https://coronavirus.jhu.edu/map.html). Even though vaccines currently used have high efficacy (1, 2) and undoubtedly, have reduced COVID-19 mortality and severe disease in countries that accelerated mass immunization (3), breakthrough infections have been reported. As of June 1st 2021, the Centers for Disease Control and Prevention (CDC) reported that more than 135 million have been fully vaccinated in HDAC8-IN-1 the US but so far, the CDC was only notified of 3,016 cases of breakthrough infections that required hospitalization or were associated with mortality (https://www.cdc.gov/vaccines/covid-19/health-departments/breakthrough-cases.html). The frequency of asymptomatic infections though might be underestimated and the relationship between the immune status, viral loads, and recovery of infectious computer virus from vaccinated positives are largely not known. With the appearance of SARS-CoV-2 variants that are more transmissible or capable of evading vaccine induced immune responses, surveillance has become of utmost importance and genome characterization of positives after vaccination is essential. Currently, data support that vaccines approved for use in the US are effective against most of the currently circulating variants (4)(5). With the general increase in the circulation of variants of concern, it is expected to see a high percentage of breakthrough infections caused by these variants. In our laboratory, as a part of high throughput sequencing for surveillance, positives after full vaccination are genotyped. In addition, viruses are characterized on cell culture to determine the association of computer virus genotypes and RNA loads with the recovery of infectious computer virus. In this manuscript, we provide a HDAC8-IN-1 comprehensive analysis of 133 positives after vaccination diagnosed by Johns Hopkins Clinical Microbiology laboratory. Samples were enrolled in our whole genome sequencing for surveillance pipeline and were retested by the PerkinElmer PCR assay to obtain comparable cycle threshold values (Cts). The recovery of infectious computer virus from positives after vaccination was decided as well as local SARS-CoV-2 IgG levels in the respiratory samples using ELISA and compared to a control unvaccinated cohort. Methods Ethical considerations and Data availability The research Johns Hopkins Medical Institutions Institutional Review Board-X (JHM IRB-X) is usually constituted to meet the requirements of the Privacy Rule at section 45 CFR 164.512(i)(1)(i)(B) and is authorized and competent to serve as the Privacy Board for human subjects research applications conducted by Johns Hopkins University faculty members. JHM IRB-3 approved IRB00221396 entitled Genomic evolution of viral pathogens: impact on clinical severity and molecular diagnosis. IRB review included the granting of a waiver of consent based on the following criteria: 1) the research involves no more than minimal risk to subjects; 2) the waiver will not adversely affect the rights and welfare of the subjects; 3) the research could not be practicably carried out without the waiver; and 4) the IRB will advise if it is appropriate for participants to be provided with additional.