We use a mathematical model to simulate the dynamics of wild-type and variant strains of SARS-CoV-2 in the context of vaccine rollout and nonpharmaceutical interventions. We show that variants with enhanced transmissibility frequently increase epidemic severity, whereas those with partial immune escape either fail to spread widely or primarily cause reinfections and breakthrough infections. However, when these phenotypes are combined, a variant can continue spreading even as immunity builds up in the population, limiting the impact of vaccination and exacerbating the epidemic.

We show a steep and near complete replacement of circulating variants with Delta between May and August 2021 in metropolitan New York. We observed an increase of the Delta sublineage AY.25, its spike mutation S112L, and nsp12 mutation F192V in breakthroughs. Delta infections were associated with younger age and lower hospitalization rates than Alpha. Delta breakthroughs increased significantly with time since vaccination, and, after adjusting for confounders, they rose at similar rates as in unvaccinated individuals. Our data indicate a limited impact of vaccine escape in favor of Delta's increased epidemic growth in times of waning vaccine protection.

CDC has collaborated with partners to model scenarios of the epidemic trajectory in the U.S. that simultaneously consider transmissibility and immune evasion. Results from scenario analyses indicate that current increases in Omicron cases are likely to lead to a national surge in the coming weeks with peak daily numbers of new infections that could exceed previous peaks; these scenarios may be realized as soon as January. In scenarios with lower immune evasion, a surge is still likely, but the peak could be lower and begin as late as April 2022. Projected large surges in cases indicate surges of hospital demand even if severity is reduced, because of the large number of anticipated cases occurring in a short period of time.

Our study provides evidence of protection against infection with the Omicron variant after completion of a primary vaccination series with the BNT162b2 or mRNA-1273 vaccines; in particular, we found a VE against the Omicron variant of 55.2% (95% confidence interval (CI): 23.5 to 73.7%) and 36.7% (95% CI: -69.9 to 76.4%) for the BNT162b2 and mRNA-1273 vaccines, respectively, in the first month after primary vaccination. However, the VE is significantly lower than that against Delta infection and declines rapidly over just a few months. The VE is re-established upon revaccination with the BNT162b2 vaccine (54.6%, 95% CI: 30.4 to 70.4%).

All vaccines apart from Ad26.CoV2.S showed high levels of responder rates (93.3-100%) towards SARS-CoV-2 wild-type, but some reductions in neutralizing Beta and Delta VoC pseudotypes. The novel Omicron variant had the biggest impact, both in terms of response rates and neutralization titres among responders. Only mRNA-1273 showed a 100% response rate to Omicron and induced the highest titres of neutralizing antibodies, followed by heterologous prime-boost approaches

Emerging variants of concern (VOC) drive the SARS-CoV-2 pandemic1,2. Experimental assessment of replication and transmission of major VOC compared to progenitors are needed to understand successful emerging mechanisms of VOC3. Here, we show that Alpha and Beta spike (S) proteins have a greater affinity to human angiotensin converting enzyme 2 (hACE2) receptor over the progenitor variant (wt-S614G) in vitro. Yet Alpha and wt-S614G had similar replication kinetics in human nasal airway epithelial cultures, whereas Beta was outcompeted by both.

It is not fully understood why COVID-19 is typically milder in children1–3. To examine differences in response to SARS-CoV-2 infection in children and adults, we analysed paediatric and adult COVID-19 patients and healthy controls (total n=93) using single-cell multi-omic profiling of matched nasal, tracheal, bronchial and blood samples. Our matching nasal and blood data showed a strong interferon response in the airways with the induction of systemic interferon-stimulated populations, which were massively reduced in pediatric patients. Together, we provide several mechanisms that explain the milder clinical syndrome observed in children.

Compared to earlier Delta infections, after controlling for factors associated with severe disease, SGTF-infected individuals had a lower odds of severe disease (aOR 0.3, 95% CI 0.2-0.6). Conclusion Early analyses suggest a reduced risk of hospitalization among SGTF-infected individuals when compared to non-SGTF infected individuals in the same time period, and a reduced risk of severe disease when compared to earlier Delta-infected individuals. Some of this reduction is likely a result of high population immunity.

We use a mathematical model to simulate the dynamics of wild-type and variant strains of SARS-CoV-2 in the context of vaccine rollout and nonpharmaceutical interventions. We show that variants with enhanced transmissibility frequently increase epidemic severity, whereas those with partial immune escape either fail to spread widely or primarily cause reinfections and breakthrough infections. However, when these phenotypes are combined, a variant can continue spreading even as immunity builds up in the population, limiting the impact of vaccination and exacerbating the epidemic.

We show a steep and near complete replacement of circulating variants with Delta between May and August 2021 in metropolitan New York. We observed an increase of the Delta sublineage AY.25, its spike mutation S112L, and nsp12 mutation F192V in breakthroughs. Delta infections were associated with younger age and lower hospitalization rates than Alpha. Delta breakthroughs increased significantly with time since vaccination, and, after adjusting for confounders, they rose at similar rates as in unvaccinated individuals. Our data indicate a limited impact of vaccine escape in favor of Delta's increased epidemic growth in times of waning vaccine protection.

CDC has collaborated with partners to model scenarios of the epidemic trajectory in the U.S. that simultaneously consider transmissibility and immune evasion. Results from scenario analyses indicate that current increases in Omicron cases are likely to lead to a national surge in the coming weeks with peak daily numbers of new infections that could exceed previous peaks; these scenarios may be realized as soon as January. In scenarios with lower immune evasion, a surge is still likely, but the peak could be lower and begin as late as April 2022. Projected large surges in cases indicate surges of hospital demand even if severity is reduced, because of the large number of anticipated cases occurring in a short period of time.

Our study provides evidence of protection against infection with the Omicron variant after completion of a primary vaccination series with the BNT162b2 or mRNA-1273 vaccines; in particular, we found a VE against the Omicron variant of 55.2% (95% confidence interval (CI): 23.5 to 73.7%) and 36.7% (95% CI: -69.9 to 76.4%) for the BNT162b2 and mRNA-1273 vaccines, respectively, in the first month after primary vaccination. However, the VE is significantly lower than that against Delta infection and declines rapidly over just a few months. The VE is re-established upon revaccination with the BNT162b2 vaccine (54.6%, 95% CI: 30.4 to 70.4%).

All vaccines apart from Ad26.CoV2.S showed high levels of responder rates (93.3-100%) towards SARS-CoV-2 wild-type, but some reductions in neutralizing Beta and Delta VoC pseudotypes. The novel Omicron variant had the biggest impact, both in terms of response rates and neutralization titres among responders. Only mRNA-1273 showed a 100% response rate to Omicron and induced the highest titres of neutralizing antibodies, followed by heterologous prime-boost approaches

Emerging variants of concern (VOC) drive the SARS-CoV-2 pandemic1,2. Experimental assessment of replication and transmission of major VOC compared to progenitors are needed to understand successful emerging mechanisms of VOC3. Here, we show that Alpha and Beta spike (S) proteins have a greater affinity to human angiotensin converting enzyme 2 (hACE2) receptor over the progenitor variant (wt-S614G) in vitro. Yet Alpha and wt-S614G had similar replication kinetics in human nasal airway epithelial cultures, whereas Beta was outcompeted by both.

It is not fully understood why COVID-19 is typically milder in children1–3. To examine differences in response to SARS-CoV-2 infection in children and adults, we analysed paediatric and adult COVID-19 patients and healthy controls (total n=93) using single-cell multi-omic profiling of matched nasal, tracheal, bronchial and blood samples. Our matching nasal and blood data showed a strong interferon response in the airways with the induction of systemic interferon-stimulated populations, which were massively reduced in pediatric patients. Together, we provide several mechanisms that explain the milder clinical syndrome observed in children.

Compared to earlier Delta infections, after controlling for factors associated with severe disease, SGTF-infected individuals had a lower odds of severe disease (aOR 0.3, 95% CI 0.2-0.6). Conclusion Early analyses suggest a reduced risk of hospitalization among SGTF-infected individuals when compared to non-SGTF infected individuals in the same time period, and a reduced risk of severe disease when compared to earlier Delta-infected individuals. Some of this reduction is likely a result of high population immunity.

We use a mathematical model to simulate the dynamics of wild-type and variant strains of SARS-CoV-2 in the context of vaccine rollout and nonpharmaceutical interventions. We show that variants with enhanced transmissibility frequently increase epidemic severity, whereas those with partial immune escape either fail to spread widely or primarily cause reinfections and breakthrough infections. However, when these phenotypes are combined, a variant can continue spreading even as immunity builds up in the population, limiting the impact of vaccination and exacerbating the epidemic.

We show a steep and near complete replacement of circulating variants with Delta between May and August 2021 in metropolitan New York. We observed an increase of the Delta sublineage AY.25, its spike mutation S112L, and nsp12 mutation F192V in breakthroughs. Delta infections were associated with younger age and lower hospitalization rates than Alpha. Delta breakthroughs increased significantly with time since vaccination, and, after adjusting for confounders, they rose at similar rates as in unvaccinated individuals. Our data indicate a limited impact of vaccine escape in favor of Delta's increased epidemic growth in times of waning vaccine protection.

CDC has collaborated with partners to model scenarios of the epidemic trajectory in the U.S. that simultaneously consider transmissibility and immune evasion. Results from scenario analyses indicate that current increases in Omicron cases are likely to lead to a national surge in the coming weeks with peak daily numbers of new infections that could exceed previous peaks; these scenarios may be realized as soon as January. In scenarios with lower immune evasion, a surge is still likely, but the peak could be lower and begin as late as April 2022. Projected large surges in cases indicate surges of hospital demand even if severity is reduced, because of the large number of anticipated cases occurring in a short period of time.

Our study provides evidence of protection against infection with the Omicron variant after completion of a primary vaccination series with the BNT162b2 or mRNA-1273 vaccines; in particular, we found a VE against the Omicron variant of 55.2% (95% confidence interval (CI): 23.5 to 73.7%) and 36.7% (95% CI: -69.9 to 76.4%) for the BNT162b2 and mRNA-1273 vaccines, respectively, in the first month after primary vaccination. However, the VE is significantly lower than that against Delta infection and declines rapidly over just a few months. The VE is re-established upon revaccination with the BNT162b2 vaccine (54.6%, 95% CI: 30.4 to 70.4%).

All vaccines apart from Ad26.CoV2.S showed high levels of responder rates (93.3-100%) towards SARS-CoV-2 wild-type, but some reductions in neutralizing Beta and Delta VoC pseudotypes. The novel Omicron variant had the biggest impact, both in terms of response rates and neutralization titres among responders. Only mRNA-1273 showed a 100% response rate to Omicron and induced the highest titres of neutralizing antibodies, followed by heterologous prime-boost approaches

Emerging variants of concern (VOC) drive the SARS-CoV-2 pandemic1,2. Experimental assessment of replication and transmission of major VOC compared to progenitors are needed to understand successful emerging mechanisms of VOC3. Here, we show that Alpha and Beta spike (S) proteins have a greater affinity to human angiotensin converting enzyme 2 (hACE2) receptor over the progenitor variant (wt-S614G) in vitro. Yet Alpha and wt-S614G had similar replication kinetics in human nasal airway epithelial cultures, whereas Beta was outcompeted by both.

It is not fully understood why COVID-19 is typically milder in children1–3. To examine differences in response to SARS-CoV-2 infection in children and adults, we analysed paediatric and adult COVID-19 patients and healthy controls (total n=93) using single-cell multi-omic profiling of matched nasal, tracheal, bronchial and blood samples. Our matching nasal and blood data showed a strong interferon response in the airways with the induction of systemic interferon-stimulated populations, which were massively reduced in pediatric patients. Together, we provide several mechanisms that explain the milder clinical syndrome observed in children.

Compared to earlier Delta infections, after controlling for factors associated with severe disease, SGTF-infected individuals had a lower odds of severe disease (aOR 0.3, 95% CI 0.2-0.6). Conclusion Early analyses suggest a reduced risk of hospitalization among SGTF-infected individuals when compared to non-SGTF infected individuals in the same time period, and a reduced risk of severe disease when compared to earlier Delta-infected individuals. Some of this reduction is likely a result of high population immunity.