Delta variants of SARS-CoV-2 cause significantly increased vaccine breakthrough COVID-19 cases in Houston, Texas

Abstract

Genetic variants of SARS-CoV-2 have repeatedly altered the course of the COVID-19 pandemic, and disease in individual patients. Delta variants (B.1.617.2, AY.2, and AY.3) are now the focus of international concern because they are causing widespread COVID-19 disease globally. Vaccine breakthrough cases caused by SARS-CoV-2 variants also are of considerable public health and medical concern worldwide. As part of a comprehensive project, we sequenced the genomes of 3,913 SARS-CoV-2 from patient samples acquired March 15, 2021 through July 3, 2021 in the Houston Methodist hospital system and studied vaccine breakthrough cases. During the study period Delta variants increased to cause 58% of all COVID-19 cases and spread throughout the metropolitan Houston area. In addition, Delta variants caused a significantly higher rate of vaccine breakthrough cases (19.7% compared to 5.8% for all other variants). Importantly, only 6.5% of all COVID-19 cases occurred in fully immunized individuals, and relatively few of these patients required hospitalization. Our genomic and epidemiologic data emphasize that vaccines used in the United States are highly effective in decreasing severe COVID-19 disease, hospitalizations, and deaths.

Intranasal vaccination with a Newcastle disease virus-vectored vaccine protects hamsters from SARS-CoV-2 infection and disease

“…The COVID-19 pandemic has seen an unprecedented number of vaccine candidates, with as many as 14 approved for use in at least one country (Organization). Given the evolution of novel variants of concern (Kirola, 2021;van Oosterhout et al, 2021), the likelihood of persistent spread of SARS-CoV-2 for several years (Scudellari, 2020), emerging data which suggest that the Delta variant may spread more readily than other SARS-CoV-2 variants among people vaccinated against COVID-19 (Brown et al, 2021;Musser et al, 2021;Riemersma et al, 2021), limitations in production capacity of developed vaccines (Khamsi, 2020), and the need for evidence of efficacy for multiple platforms moving forward, there will be a need for a diverse set of vaccine candidates to advance through all stages of development. Here we tested two live vaccine candidates based on an NDV vector expressing SARS-CoV-2 spike protein or a truncated version of the same protein in a hamster model to assess their potential for prevention of COVID-19.…”

Effectiveness of inactive COVID-19 vaccines against severe illness in B.1.617.2 (Delta) variant-infected patients in Jiangsu, China

“…Although an entire course of vaccination could efficiently protect the COVID-19 patients from progressing to severe illness, the protective effect could not be identified in partially vaccinated ones. This may be due to a relatively high viral burden and a decreased immune protection in Delta variant-infected patients [19, 20, 29]. The baseline viral load in this study, as represented by Ct value of the real-time quantitative reverse transcription polymerase chain reaction (RT-PCR) was 20 (IQR: 16-25), which is much higher than that (median: 30; IQR: 25-34) in our previous data during the first outbreak of COVID-19 in 2020[31].…”

“…Compared with the original type of SARS-CoV-2, the Delta variant has a significantly increased virulence and transmission ability[14, 15, 16]. Furthermore, the protective effect of vaccines against Delta variant infection is found to be weakened in many studies[17, 18, 19, 20, 21].…”

An Analysis of SARS-CoV-2 Vaccine Breakthrough Infections and Associated Clinical Outcomes

“…These findings add to a growing body of data that can reassure the public on the real-world effectiveness of the COVID-19 vaccines. 2…”