Modelling the impact of extending dose intervals for COVID-19 vaccines in Canada
This article has been Reviewed by the following groups
Listed in
- Evaluated articles (ScreenIT)
Abstract
Background
Dual dose SARS-CoV-2 vaccines demonstrate high efficacy and will be critical in public health efforts to mitigate the COVID-19 pandemic and its health consequences; however, many jurisdictions face very constrained vaccine supply. We examined the impacts of extending the interval between two doses of mRNA vaccines in Canada in order to inform deliberations of Canada’s National Advisory Committee on Immunization.
Methods
We developed an age-stratified, deterministic, compartmental model of SARS-CoV-2 transmission and disease to reproduce the epidemiologic features of the epidemic in Canada. Simulated vaccination comprised mRNA vaccines with explicit examination of effectiveness against disease (67% [first dose], 94% [second dose]), hospitalization (80% [first dose], 96% [second dose]), and death (85% [first dose], 96% [second dose]) in adults aged 20 years and older. Effectiveness against infection was assumed to be 90% relative to the effectiveness against disease. We used a 6-week mRNA dose interval as our base case (consistent with early program rollout across Canadian and international jurisdictions) and compared extended intervals of 12 weeks, 16 weeks, and 24 weeks. We began vaccinations on January 1, 2021 and simulated a third wave beginning on April 1, 2021.
Results
Extending mRNA dose intervals were projected to result in 12.1-18.9% fewer symptomatic cases, 9.5-13.5% fewer hospitalizations, and 7.5-9.7% fewer deaths in the population over a 12-month time horizon. The largest reductions in hospitalizations and deaths were observed in the longest interval of 24 weeks, though benefits were diminishing as intervals extended. Benefits of extended intervals stemmed largely from the ability to accelerate coverage in individuals aged 20-74 years as older individuals were already prioritized for early vaccination. Conditions under which mRNA dose extensions led to worse outcomes included: first-dose effectiveness < 65% against death; or protection following first dose waning to 0% by month three before the scheduled 2 nd dose at 24-weeks. Probabilistic simulations from a range of likely vaccine effectiveness values did not result in worse outcomes with extended intervals.
Conclusion
Under real-world effectiveness conditions, our results support a strategy of extending mRNA dose intervals across all age groups to minimize symptomatic cases, hospitalizations, and deaths while vaccine supply is constrained.
Article activity feed
-
SciScore for 10.1101/2021.04.07.21255094: (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
No key resources detected.
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:There are some limitations to the present study. First, our model stratified risk by age and was used to inform broad population-based vaccination strategies but was not designed to examine other high-risk groups such as immunocompromised individuals for whom extended intervals may not be an optimal strategy. Second, we did not consider …
SciScore for 10.1101/2021.04.07.21255094: (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
No key resources detected.
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:There are some limitations to the present study. First, our model stratified risk by age and was used to inform broad population-based vaccination strategies but was not designed to examine other high-risk groups such as immunocompromised individuals for whom extended intervals may not be an optimal strategy. Second, we did not consider long-term implications of immune responses, vaccine escape, and variants of concern. However, the third wave simulated in our model and our sensitivity analyses could be considered as a proxy for variant of concern scenarios with higher transmission rates, variable vaccine effectiveness or waning protection. Our sensitivity analyses can inform ongoing evaluation of extended intervals if effectiveness begins to diminish or waning protection accelerates. In addition, we used a simplistic epidemic scenario and did not simulate scenarios of dynamic public health measures that may be deployed to confront a third wave or any subsequent resurgences following implementation of additional public health measures. Our model adds to the current literature examining different mRNA dose interval strategies with explicit consideration of real-world effectiveness against symptomatic disease, hospitalizations and death. Strategies of extended intervals were examined in the context of the early COVID-19 vaccination campaign in Canada. Further, our model findings can be used to inform ongoing monitoring of extended interval strategies as effectiveness data conti...
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.
-
