Will Vaccine-derived Protective Immunity Curtail COVID-19 Variants in the US?
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Abstract
Multiple effective vaccines are currently being deployed to combat the COVID-19 pandemic, and are viewed as the major factor in marked reductions of disease burden in regions with moderate to high vaccination coverage. The effectiveness of COVID-19 vaccination programs is, however, significantly threatened by the emergence of new SARS-COV-2 variants that, in addition to being more transmissible than the wild-type (original) strain, may at least partially evade existing vaccines. A two-strain (one wild-type, one variant) and two-group (vaccinated or otherwise) mechanistic mathematical model is designed and used to assess the impact of the vaccine-induced cross-protective efficacy on the spread the COVID-19 pandemic in the United States. Rigorous analysis of the model shows that, in the absence of any co-circulating SARS-CoV-2 variant, the vaccine-derived herd immunity threshold needed to eliminate the wild-type strain can be achieved if 59% of the US population is fully-vaccinated with either the Pfizer or Moderna vaccine. This threshold increases to 76% if the wild-type strain is co-circulating with the Alpha variant (a SARS-CoV-2 variant that is 56% more transmissible than the wild-type strain). If the wild-type strain is co-circulating with the Delta variant (which is estimated to be 100% more transmissible than the wild-type strain), up to 82% of the US population needs to be vaccinated with either of the aforementioned vaccines to achieve the vaccine-derived herd immunity. Global sensitivity analysis of the model reveal the following four parameters as the most influential in driving the value of the reproduction number of the variant strain (hence, COVID-19 dynamics) in the US: (a) the infectiousness of the co-circulating SARS-CoV-2 variant, (b) the proportion of individuals fully vaccinated (using Pfizer or Moderna vaccine) against the wild-type strain, (c) the cross-protective efficacy the vaccines offer against the variant strain and (d) the modification parameter accounting for the reduced infectiousness of fully-vaccinated individuals experiencing breakthrough infection. Specifically, numerical simulations of the model show that future waves or surges of the COVID-19 pandemic can be prevented in the US if the two vaccines offer moderate level of cross-protection against the variant (at least 67%). This study further suggests that a new SARS-CoV-2 variant can cause a significant disease surge in the US if (i) the vaccine coverage against the wild-type strain is low (roughly < 66%), (ii) the variant is much more transmissible (e.g., 100% more transmissible) than the wild-type strain, or (iii) the level of cross-protection offered by the vaccine is relatively low (e.g., less than 50%). A new SARS-CoV-2 variant will not cause such surge in the US if it is only moderately more transmissible (e.g., the Alpha variant, which is 56% more transmissible) than the wild-type strain, at least 66% of the population of the US is fully vaccinated, and the three vaccines being deployed in the US (Pfizer, Moderna, and Johnson & Johnson) offer a moderate level of cross-protection against the variant.
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SciScore for 10.1101/2021.06.30.21259782: (What is this?)
Please note, not all rigor criteria are appropriate for all manuscripts.
Table 1: Rigor
NIH rigor criteria are not applicable to paper type.Table 2: Resources
Software and Algorithms Sentences Resources We use a MATLAB routine to minimize the sum of squared differences between each observed cumulative mortality data point and the corresponding mortality point obtained from the model (A-8). MATLABsuggested: (MATLAB, RRID:SCR_001622)Results from OddPub: We did not detect open data. We also did not detect open code. Researchers are encouraged to share open data when possible (see Nature blog).
Results from LimitationRecognizer: We detected the following sentences addressing limitations in the study:Moreover, another limitation of the current framework of the model (A-8) is that it can only …
SciScore for 10.1101/2021.06.30.21259782: (What is this?)
Please note, not all rigor criteria are appropriate for all manuscripts.
Table 1: Rigor
NIH rigor criteria are not applicable to paper type.Table 2: Resources
Software and Algorithms Sentences Resources We use a MATLAB routine to minimize the sum of squared differences between each observed cumulative mortality data point and the corresponding mortality point obtained from the model (A-8). MATLABsuggested: (MATLAB, RRID:SCR_001622)Results from OddPub: We did not detect open data. We also did not detect open code. Researchers are encouraged to share open data when possible (see Nature blog).
Results from LimitationRecognizer: We detected the following sentences addressing limitations in the study:Moreover, another limitation of the current framework of the model (A-8) is that it can only analyze one variant strain of SARS-CoV-2. Extension of this model could include multiple variant strains to determine the individual and collective impact on the COVID-19 pandemic. Since current studies show that naturally-acquired immunity is less likely to produce an immune response to the existing variants than vaccination (52; 30), another future extension of the model (A-8) could include the possibility that individuals who recovered from the wild-type strain (R1 class) could be directly infected by the variant strain without losing developed immunity from the wild-type strain. This would alter the vaccination reproduction number and basic reproduction number expressions of the model (A-8). The B.1.1.7 is currently the most dominant variant circulating in the US population (12; 16), and estimated to be 56% more infectious than the wild-type strain (20). The numerical simulations showed that if a moderate level of vaccination coverage (≥ 66% of the US population) and moderately-high level of cross-protective vaccination efficacy (εc ≥ 0.7) is attained, then a surge of variant-induced COVID-19 infections and mortality will not occur (under the assumption that both vaccine and naturally-acquired immunity lasts at least two years). One study showed that cross-protective efficacy is as high as 93% against the B.1.1.7 variant when two doses of the Pfizer vaccine are administered, but d...
Results from TrialIdentifier: No clinical trial numbers were referenced.
Results from Barzooka: We did not find any issues relating to the usage of bar graphs.
Results from JetFighter: We did not find any issues relating to colormaps.
Results from rtransparent:- Thank you for including a conflict of interest statement. Authors are encouraged to include this statement when submitting to a journal.
- Thank you for including a funding statement. Authors are encouraged to include this statement when submitting to a journal.
- No protocol registration statement was detected.
Results from scite Reference Check: We found no unreliable references.
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