The minimal COVID-19 vaccination coverage and efficacy to compensate for a potential increase of transmission contacts, and increased transmission probability of the emerging strains.

BACKGROUND: Mass immunization is a potentially effective approach to finally control the local outbreak and global spread of the COVID-19 pandemic. However, it can also lead to undesirable outcomes if mass vaccination results in increased transmission of effective contacts and relaxation of other public health interventions due to the perceived immunity from the vaccine. METHODS: We designed a mathematical model of COVID-19 transmission dynamics that takes into consideration the epidemiological status, public health intervention status (quarantined/isolated), immunity status of the population, and strain variations. Comparing the control reproduction numbers and the final epidemic sizes (attack rate) in the cases with and without vaccination, we quantified some key factors determining when vaccination in the population is beneficial for preventing and controlling future outbreaks. RESULTS: Our analyses predicted that there is a critical (minimal) vaccine efficacy rate (or a critical quarantine rate) below which the control reproduction number with vaccination is higher than that without vaccination, and the final attack rate in the population is also higher with the vaccination. We also predicted the worst case scenario occurs when a high vaccine coverage rate is achieved for a vaccine with a lower efficacy rate and when the vaccines increase the transmission efficient contacts. CONCLUSIONS: The analyses show that an immunization program with a vaccine efficacy rate below the predicted critical values will not be as effective as simply investing in the contact tracing/quarantine/isolation implementation. We reached similar conclusions by considering the final epidemic size (or attack rates). This research then highlights the importance of monitoring the impact on transmissibility and vaccine efficacy of emerging strains.

Considering Strain Variation and Non-Type Strains for Yeast Metabolic Engineering Applications.

A variety of yeast species have been considered ideal hosts for metabolic engineering to produce value-added chemicals, including the model organism Saccharomyces cerevisiae, as well as non-conventional yeasts including Yarrowia lipolytica, Kluyveromyces marxianus, and Pichia pastoris. However, the metabolic capacity of these microbes is not simply dictated or implied by genus or species alone. Within the same species, yeast strains can display distinct variations in their phenotypes and metabolism, which affect the performance of introduced pathways and the production of interesting compounds. Moreover, it is unclear how this metabolic potential corresponds to function upon rewiring these organisms. These reports thus point out a new consideration for successful metabolic engineering, specifically: what are the best strains to utilize and how does one achieve effective metabolic engineering? Understanding such questions will accelerate the host selection and optimization process for generating yeast cell factories. In this review, we survey recent advances in studying yeast strain variations and utilizing non-type strains in pathway production and metabolic engineering applications. Additionally, we highlight the importance of employing portable methods for metabolic rewiring to best access this metabolic diversity. Finally, we conclude by highlighting the importance of considering strain diversity in metabolic engineering applications.

Intratendinous Strain Variations of the Supraspinatus Tendon Depending on Repair Technique: A Biomechanical Analysis Regarding the Cause of Medial Cuff Failure.

BACKGROUND: Double-row (DR) and transosseous-equivalent (TOE) techniques for rotator cuff repair offer more stability and promote better tendon healing compared with single-row (SR) repairs and are preferred by many surgeons. However, they can lead to more disastrous retear patterns with failure at the medial anchor row or the musculotendinous junction. The biomechanics of medial cuff failure have not been thoroughly investigated thus far. PURPOSE: To investigate the intratendinous strain distribution within the supraspinatus tendon depending on repair technique. STUDY DESIGN: Controlled laboratory study. METHODS: Twelve fresh-frozen cadaveric shoulders were used. The intratendinous strain within the supraspinatus tendon was analyzed in 2 regions-(1) at the footprint at the greater tuberosity and (2) medial to the footprint up to the musculotendinous junction-using a high-resolution 3-dimensional camera system. Testing was performed at submaximal loads of 40 N, 60 N, and 80 N for intact tendons, after SR repair, after DR repair, and after TOE repair. RESULTS: The tendon strain of the SR group differed significantly in both regions from that of the intact tendons and the TOE group at 40 N (P≤ .043) and from the intact tendons, the DR group, and the TOE group at 60 N and 80 N (P≤ .048). SR repairs showed more tendon elongation at the footprint and less elongation medial to the footprint. DR and TOE repairs did not provide significant differences in tendon strain when compared with the intact tendons. However, the increase in tendon strain medial to the footprint from 40 N to 80 N was significantly more pronounced in the DR and TOE group (P≤ .029). CONCLUSION: While DR and TOE repair techniques more closely reproduced the strains of the supraspinatus tendon than did SR repair in a cadaveric model, they showed a significantly increased tendon strain at the musculotendinous junction with higher loads in comparison with the intact tendon. CLINICAL RELEVANCE: DR and TOE rotator cuff reconstructions lead to a more anatomic tendon repair. However, their use has to be carefully evaluated whenever tendon quality is diminished, as they lead to a more drastic increase in tendon strain medial to the footprint, putting these repairs at risk of medial cuff failure.