Modeling waning and boosting of COVID-19 in Canada with vaccination

Abstract

SARS-CoV-2, the causative agent of COVID-19, has caused devastating health and economic impacts around the globe since its appearance in late 2019. The advent of effective vaccines leads to open questions on how best to vaccinate the population. To address such questions, we developed a model of COVID-19 infection by age that includes the waning and boosting of immunity against SARS-CoV-2 in the context of infection and vaccination. The model also accounts for changes to infectivity of the virus, such as public health mitigation protocols over time, increases in the transmissibility of variants of concern, changes in compliance to mask wearing and social distancing, and changes in testing rates. The model is employed to study public health mitigation and vaccination of the COVID-19 epidemic in Canada, including different vaccination programs (rollout by age), and delays between doses in a two-dose vaccine. We find that the decision to delay the second dose of vaccine is appropriate in the Canadian context. We also find that the benefits of a COVID-19 vaccination program in terms of reductions in infections is increased if vaccination of 15-19 year olds are included in the vaccine rollout.

Barrier Gesture Relaxation during Vaccination Campaign in France: Modelling Impact of Waning Immunity

“…, 75+ years). As in Childs et al [33], we use S im , E k jm , I jm , and V l im to denote the number of susceptible, exposed, infectious, and vaccinated individuals in each age group m (1 ≤ m ≤ 16), where i (1 ≤ i ≤ 4) denotes immune status, j (2 ≤ j ≤ 4) denotes symptom severity, k (1 ≤ k ≤ 3) represents stages in the exposed class, and l (1 ≤ l ≤ 2) denotes the number of vaccine doses that individuals have received.…”

“…We used a compartmental age-structured model of COVID-19 infection previously developed by Childs et al [33] which is adapted from a model of vaccination and waning immunity applied to pertussis [34]. A flow diagram of the model is shown in Figure 1 for a single age group.…”

“…A flow diagram of the model is shown in a single age group. The model is based on a Susceptible-Exposed-Infected-Susceptible model structure (SEIVS) with age structure (i.e., groups 0-4, 5-9,.. As in Childs et al [33], we use Sim, E k jm, Ijm, and V l im to denote the number of exposed, infectious, and vaccinated individuals in each age group m (1 ≤ m ≤ (1 ≤ i ≤ 4) denotes immune status, j (2 ≤ j ≤ 4) denotes symptom severity, k represents stages in the exposed class, and l (1 ≤ l ≤ 2) denotes the number of v that individuals have received. [33].…”

“…The model is based on a Susceptible-Exposed-Infected-Susceptible model structure (SEIVS) with age structure (i.e., groups 0-4, 5-9,.. As in Childs et al [33], we use Sim, E k jm, Ijm, and V l im to denote the number of exposed, infectious, and vaccinated individuals in each age group m (1 ≤ m ≤ (1 ≤ i ≤ 4) denotes immune status, j (2 ≤ j ≤ 4) denotes symptom severity, k represents stages in the exposed class, and l (1 ≤ l ≤ 2) denotes the number of v that individuals have received. [33]. Here, S1, S2, S3, and S4 (blue shaded boxes) represent susceptible individuals susceptible, have some low and moderate immunity, and full immunity, respectivel (yellow boxes) represent infected individuals with mild, moderate, and severe symp tively, who will develop some low, moderate, or full immunity once recovered (yell spectively.…”

“…Immunity develops after infection. It is assumed that people with erate, and severe symptoms move to immune classes S2, S3, and S4, respective [33]. Here, S 1 , S 2 , S 3 , and S 4 (blue shaded boxes) represent susceptible individuals who are fully susceptible, have some low and moderate immunity, and full immunity, respectively.…”