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Review 2: "Estimated transmissibility and severity of novel SARS-CoV-2 Variant of Concern 202012/01 in England"

This potentially informative study models the spread of 501Y.V1 in England, and suggests more stringent control measures and increased vaccinations are necessary to prevent spread of these variants.

Published onFeb 10, 2021
Review 2: "Estimated transmissibility and severity of novel SARS-CoV-2 Variant of Concern 202012/01 in England"
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key-enterThis Pub is a Review of
Estimated transmissibility and severity of novel SARS-CoV-2 Variant of Concern 202012/01 in England

A novel SARS-CoV-2 variant, VOC 202012/01, emerged in southeast England in November 2020 and is rapidly spreading towards fixation. Using a variety of statistical and dynamic modelling approaches, we assessed the relative transmissibility of this novel variant. Depending on the analysis, we estimate that VOC 202012/01 is 43–82% (range of 95% credible intervals 38–106%) more transmissible than preexisting variants of SARS-CoV-2. We did not find clear evidence that VOC 202012/01 results in greater or lesser severity of disease than preexisting variants. Nevertheless, the increase in transmissibility is likely to lead to a large increase in incidence. To assess the potential impact of VOC 202012/01, we fitted a two-strain mathematical model of SARS-CoV-2 transmission to observed COVID-19 hospital admissions, hospital and ICU bed occupancy, and deaths; SARS-CoV-2 PCR prevalence and seroprevalence; and the relative frequency of VOC 202012/01. We find that without stringent control measures, COVID-19 hospitalisations and deaths are projected to reach higher levels in 2021 than were observed in 2020. Control measures of a similar stringency to the national lockdown implemented in England in November 2020 are unlikely to reduce the effective reproduction number Rt to less than 1, unless primary schools, secondary schools, and universities are also closed. We project that large resurgences of the virus are likely to occur following easing of control measures. It may be necessary to greatly accelerate vaccine roll-out to have an appreciable impact in suppressing the resulting disease burden.

RR:C19 Evidence Scale rating by reviewer:

  • Potentially informative. The main claims made are not strongly justified by the methods and data, but may yield some insight. The results and conclusions of the study may resemble those from the hypothetical ideal study, but there is substantial room for doubt. Decision-makers should consider this evidence only with a thorough understanding of its weaknesses, alongside other evidence and theory. Decision-makers should not consider this actionable, unless the weaknesses are clearly understood and there is other theory and evidence to further support it.



The current report by Nicholas et al estimates the transmissibility and impacts of the novel SARS-CoV-2 Variant of Concern 202012/01 in England, also known as 501Y.V1 variant. The study design on the prediction of transmission behavior is appropriate.

The authors' concern about updating vaccination policies is justified. The represented models can also provide timely estimates to vaccine manufacturers in the wake of emerging variants.

Given the absence of data on the effects of these variants on disease severity, execution of Tier 4 or beyond measures could help reduce transmission. The authors may discuss other stringency options which might prevent further transmission.

The authors might want to discuss reliability of the models used for predictions and how their models behave compared to other models used in such analysis globally.

In conclusion, the report may provide valuable information on the spread of 501Y.V1 and other variants globally. The availability of codes such as Google mobility and Social contact data can help other researchers globally to keep check on other emerging variants.

On a scale of 1-5, I would rate strength of evidence to be 3. There are certain factors which could occlude exact modeling of the epidemic in England. Authors have thoroughly described these in detail in the Discussion section. Thus, the modeling predictions can be regarded as precautionary measures rather as actual data for media outlets.

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