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We developed a genomic surveillance program for real-time monitoring of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) variants of concern (VOCs) in Uruguay. We report on a PCR method for SARS-CoV-2 VOCs, the surveillance workflow, and multiple independent introductions and community transmission of the SARS-CoV-2 P.1 VOC in Uruguay.

COVID‐19 vaccines already in use or in clinical development may have reduced efficacy against emerging SARS‐CoV‐2 variants. In addition, although the neurotropism of SARS‐CoV‐2 is well established, the vaccine strategies currently developed have not taken into account protection of the central nervous system. Here, we generated a transgenic mouse strain expressing the human angiotensin‐converting enzyme 2, and displaying unprecedented brain permissiveness to SARS‐CoV‐2 replication, in addition to high permissiveness levels in the lung. Using this stringent transgenic model, we demonstrated that a non‐integrative lentiviral vector, encoding for the spike glycoprotein of the ancestral SARS‐CoV‐2, used in intramuscular prime and intranasal boost elicits sterilizing protection of lung and brain against both the ancestral virus, and the Gamma (P.1) variant of concern, which carries multiple vaccine escape mutations. Beyond induction of strong neutralizing antibodies, the mechanism underlying this broad protection spectrum involves a robust protective T‐cell immunity, unaffected by the recent mutations accumulated in the emerging SARS‐CoV‐2 variants. SYNOPSIS A lentiviral vector‐based vaccine, used in prime and intranasal boost, induces strong B‐ and T‐cell immunity. This vaccine candidate protects against both pulmonary and neurological COVID‐19 caused by either ancestral or emerging SARS‐CoV‐2. A new human ACE2 transgenic mouse strain provides a model to assess the efficiency of vaccine candidates against the neurological COVID‐19. A non‐integrative lentiviral vector, encoding for the ancestral SARS‐CoV‐2 Spike (LV::S), used in prime and intranasal boost, elicits strong protection of brain. LV::S induces full cross‐protection of lung and brain against Gamma (P.1) variant of concern, which carries multiple vaccine escape mutations. LV::S induces strong protective T‐cell immunity, unaffected by the recent mutations accumulated in the emerging SARS‐CoV‐2 variants. Graphical Abstract A lentiviral vector‐based vaccine, used in prime and intranasal boost, induces strong B‐ and T‐cell immunity. This vaccine candidate protects against both pulmonary and neurological COVID‐19 caused by either ancestral or emerging SARS‐CoV‐2.

The world has come a long way in the fight against the COVID-19 pandemic by averting the initially feared humanitarian crisis and by producing effective vaccines in a record time. Paradoxically, more new daily cases are being reported today than when there was not any effective vaccine around. The success against the pandemic so far is dented by inadequate vaccine supply in most low-income countries and widespread vaccine hesitancy. By the end of 2021, only half of WHO Member States have reached the target of immunizing 40% of their populations, while only less than 10% of the population in low-income countries have received at least one dose of the vaccine. This happened while more than nine billion doses of the vaccines were administered globally, predominantly in rich countries. On the backdrop of these man-made factors, the evolution of highly mutated variants of the virus is causing more uncertainties than the pre-vaccine time. If the vaccine inequities and hesitancy are not properly addressed, we are likely to enter into the vicious cycle of inequitable vaccine distribution leading to low vaccination rates in most low-income countries where the majority of the world population resides. This will ultimately enhance sustained transmission of the virus, leading to evolution of new variants of concern. As the highly mutated variants are likely to infect both vaccinated and unvaccinated individuals, it will inevitably lead to major doubts in the effectiveness and acceptance of the vaccines. In this review, we present how this vicious cycle may prolong the pandemic and discuss the importance of concerted global action to tackle it.

Rapid on‐site typing methods for SARS‐CoV‐2 variants of concern are crucial for its effective surveillance and control. Herein, a smart single‐loop‐mediated isothermal amplification (ssLAMP) method with the absence of an inner primer but the addition of a swarm primer for differentiation of SARS‐CoV‐2 Omicron variants is developed. This unique primer design strategy offers greater flexibility in introducing single nucleotide polymorphism (SNP) identification probes and enables multiple detection assays for SARS‐CoV‐2 Omicron variants including BA.1, BA.2, BA.3, BA.4, and BA.5. A 3D‐printed portable dual fluorescence visualization device and smartphone app are developed to enable point‐of‐care testing. This assay is rapid (within 90 min), highly sensitive (100 copies/reaction), and specific (identification of SNP) for SARA‐CoV‐2 Omicron variants. The ssLAMP method identifies five BA.5‐positive samples among 97 nasopharyngeal swab samples from the clinic, with a 100% concordance rate with Sanger sequencing. The ssLAMP assay system is expected to be utilized for on‐site, highly specific, and rapid visualization detection of SARS‐CoV‐2 and its variants, with great application potential in pathogen genotyping, early cancer screening, and other areas of SNP mutation detection. The ssLAMP method amplifies the nucleic acid of pathogen and identifies SNP mutations. By combining the portable detection device with smartphone‐based analysis software, enables rapid, on‐site SNP detection and genotyping of SARS‐Cov‐2 Omicron variants, providing a cost‐effective and field‐deployable solution for precise pathogen identification in clinical and resource‐limited settings.

Quantitatively describing the time course of the severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) infection within an infected individual is important for understanding the current global pandemic and possible ways to combat it. Here we integrate the best current knowledge about the typical viral load of SARS-CoV-2 in bodily fluids and host tissues to estimate the total number and mass of SARS-CoV-2 virions in an infected person. We estimate that each infected person carries 10⁹ to 1011 virions during peak infection, with a total mass in the range of 1 μg to 100 μg, which curiously implies that all SARS-CoV-2 virions currently circulating within human hosts have a collective mass of only 0.1 kg to 10 kg. We combine our estimates with the available literature on host immune response and viral mutation rates to demonstrate how antibodies markedly outnumber the spike proteins, and the genetic diversity of virions in an infected host covers all possible single nucleotide substitutions.

Our review found the effective reproduction number and basic reproduction number of the Omicron variant elicited 3.8 and 2.5 times higher transmissibility than the Delta variant, respectively. The Omicron variant has an average basic and effective reproduction number of 8.2 and 3.6.

•We investigated SARS-CoV-2 Variant-specific transmission during high-risk exposure.•Vaccination and prior infection reduced Alpha, Delta and Omicron transmission.•Escape from vaccine-induced and infection-acquired immunity was highest for Omicron.•Protection against Omicron by primary-vaccination had little effect on susceptibility.•Lower infectiousness after vaccination waned slowly and was less affected by variants. Vaccine effectiveness against transmission (VET) of SARS-CoV-2-infection can be estimated from secondary attack rates observed during contact tracing. We estimated VET, the vaccine-effect on infectiousness of the index case and susceptibility of the high-risk exposure contact (HREC). We fitted RT-PCR-test results from HREC to immunity status (vaccine schedule, prior infection, time since last immunity-conferring event), age, sex, calendar week of sampling, household, background positivity rate and dominant VOC using a multilevel Bayesian regression-model. We included Belgian data collected between January 2021 and January 2022. For primary BNT162b2-vaccination we estimated initial VET at 96% (95%CI 95–97) against Alpha, 87% (95%CI 84–88) against Delta and 31% (95%CI 25–37) against Omicron. Initial VET of booster-vaccination (mRNA primary and booster-vaccination) was 87% (95%CI 86–89) against Delta and 68% (95%CI 65–70) against Omicron. The VET-estimate against Delta and Omicron decreased to 71% (95%CI 64–78) and 55% (95%CI 46–62) respectively, 150–200 days after booster-vaccination. Hybrid immunity, defined as vaccination and documented prior infection, was associated with durable and higher or comparable (by number of antigen exposures) protection against transmission. While we observed VOC-specific immune-escape, especially by Omicron, and waning over time since immunization, vaccination remained associated with a reduced risk of SARS-CoV-2-transmission.

Severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) variants of concern (VOCs) have significantly impacted the global epidemiology of the pandemic. From December 2020 to April 2022, we conducted genomic surveillance of SARS-CoV-2 in the Southern Province of Zambia, a region that shares international borders with Botswana, Namibia, and Zimbabwe and is a major tourist destination. Genetic analysis of 40 SARS-CoV-2 whole genomes revealed the circulation of Alpha (B.1.1.7), Beta (B.1.351), Delta (AY.116), and multiple Omicron subvariants with the BA.1 subvariant being predominant. Whereas Beta, Delta, and Omicron variants were associated with the second, third, and fourth pandemic waves, respectively, the Alpha variant was not associated with any wave in the country. Phylogenetic analysis showed evidence of local transmission and possible multiple introductions of SARS-CoV-2 VOCs in Zambia from different European and African countries. Across the 40 genomes analysed, a total of 292 mutations were observed, including 182 missense mutations, 66 synonymous mutations, 23 deletions, 9 insertions, 1 stop codon, and 11 mutations in the non-coding region. This study stresses the need for the continued monitoring of SARS-CoV-2 circulation in Zambia, particularly in strategically positioned regions such as the Southern Province which could be at increased risk of introduction of novel VOCs.

The development of vaccine candidates for COVID-19 has been rapid, and those that are currently approved display high efficacy against the original circulating strains. However, recently, new variants of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) have emerged with increased transmission rates and less susceptibility to vaccine induced immunity. A greater understanding of protection mechanisms, including antibody longevity and cross-reactivity towards the variants of concern (VoCs), is needed. In this study, samples collected in Denmark early in the pandemic from paucisymptomatic subjects (n = 165) and symptomatic subjects (n = 57) infected with SARS-CoV-2 were used to assess IgG binding and inhibition in the form of angiotensin-converting enzyme 2 receptor (ACE2) competition against the wild-type and four SARS-CoV-2 VoCs (Alpha, Beta, Gamma, and Omicron). Antibodies induced early in the pandemic via natural infection were cross-reactive and inhibited ACE2 binding of the VoC, with reduced inhibition observed for the Omicron variant. When examined longitudinally, sustained cross-reactive inhibitory responses were found to exist in naturally infected paucisymptomatic subjects. After vaccination, receptor binding domain (RBD)-specific IgG binding increased by at least 3.5-fold and inhibition of ACE2 increased by at least 2-fold. When vaccination regimens were compared (two doses of Pfizer-BioNTech BNT162b2 (n = 50), or one dose of Oxford-AstraZeneca ChAdOx1 nCoV-19 followed by Pfizer-BioNTech BNT162b2 (ChAd/BNT) (n = 15)), higher levels of IgG binding and inhibition were associated with mix and match (ChAd/BNT) prime-boosting and time since vaccination. These results are particularly relevant for countries where vaccination levels are low.

Severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) is a highly transmissible coronavirus responsible for the global COVID-19 pandemic. Herein, we provide evidence that SARS-CoV-2 spreads through cell–cell contact in cultures, mediated by the spike glycoprotein. SARS-CoV-2 spike is more efficient in facilitating cell-to-cell transmission than is SARS-CoV spike, which reflects, in part, their differential cell–cell fusion activity. Interestingly, treatment of cocultured cells with endosomal entry inhibitors impairs cell-to-cell transmission, implicating endosomal membrane fusion as an underlying mechanism. Compared with cell-free infection, cell-to-cell transmission of SARS-CoV-2 is refractory to inhibition by neutralizing antibody or convalescent sera of COVID-19 patients. While angiotensin-converting enzyme 2 enhances cell-to-cell transmission, we find that it is not absolutely required. Notably, despite differences in cell-free infectivity, the authentic variants of concern (VOCs) B.1.1.7 (alpha) and B.1.351 (beta) have similar cell-to-cell transmission capability. Moreover, B.1.351 is more resistant to neutralization by vaccinee sera in cell-free infection, whereas B.1.1.7 is more resistant to inhibition by vaccinee sera in cell-to-cell transmission. Overall, our study reveals critical features of SARS-CoV-2 spike-mediated cell-to-cell transmission, with important implications for a better understanding of SARS-CoV-2 spread and pathogenesis.