COVID-19 Spreading Dynamics in an Age-Structured Population with Selective Relaxation of Restrictions for Vaccinated Individuals : a Mathematical Modeling Study

  1. B Shayak
  2. Mohit M Sharma
  3. Anand K Mishra

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Abstract

Background

COVID-19 vaccination of healthcare and other essential workers is underway in many countries while immunization of the general public is expected to begin in the next several weeks. We consider the question of whether people who have received the vaccine can be selectively and immediately permitted to return to normal activities.

Methods

We use a delay differential equation model to calculate the effects of vaccinee “immunity passports” on the epidemic spreading trajectories. The model incorporates age-structuring to account for children who are ineligible for vaccination, and senior citizens who are especially vulnerable to the disease. We consider consensus strains of virus as well as high-transmissibility variants such as B1.1.7 and B1.351 in our analysis.

Results

We find that with high vaccine efficacy of 80 percent or greater, unrestricted vaccinee—vaccinee interactions do not derail the epidemic from a path towards elimination. Vaccinee—non-vaccinee interactions should however be treated with far more caution. At current vaccine administration rates, it may be the better part of a year before COVID-19 transmission is significantly reduced or ceased. With lower vaccine efficacy of approximately 60 percent, restrictions for vaccinees may need to remain in place until the elimination of the disease is achieved. In all cases, the death tolls can be reduced by vaccinating the vulnerable population first.

Conclusions

Designing high-efficacy vaccines with easily scalable manufacturing and distribution capacity should remain on the priority list in academic as well as industrial circles. Performance of all vaccines should continue to be monitored in real time during vaccination drives with a view to analysing socio-demographic determinants of efficacy, if any, and optimizing distribution accordingly. A speedy and efficacious vaccination drive augmented with selective relaxations for vaccinees will provide the smoothest path out of the pandemic with the least additional caseloads, death tolls and socio-economic cost.

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  1. ScreenIT

    SciScore for 10.1101/2021.02.22.21252241: (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
    SentencesResources
    We solve the model using numerical integration in the software Matlab.
    Matlab
    suggested: (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:
    The limitations of the analysis come from the various assumptions in the model. One set of drawbacks is common to any lumped-parameter or compartmental model. This is that when the absolute number of cases becomes very low, the model ceases to remain valid – the deterministic evolution is replaced by a stochastic process. Hence, predictions regarding the end-stage of the outbreak, especially the time elapsed until elimination, might not be accurate. This apart, we have tried wherever possible to ensure that errors either cancel each other or occur on the side of caution. For example, the initial conditions feature a high case rate but no pre-immunized people; both of these militate against an elimination bid. We have taken minors to be as susceptible and transmissible as adults even though some evidence32 suggests that susceptibility and transmissibility might actually be lower for this group. We present a detailed discussion of the model assumptions and their effects in §2 of the Supplementary Data.

    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.

    About SciScore

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  2. Version published to 10.1101/2021.02.22.21252241v1 on medRxiv