Quantifying the effect of delaying the second COVID-19 vaccine dose in England: a mathematical modelling study

Imai, Natsuko; Rawson, Thomas; Knock, Edward; Sonabend, Raphael; Elmaci, Yasin; Perez‐Guzman, Pablo N; Whittles, Lilith K; Kanapram, Divya Thekke; Gaythorpe, Katy A. M.; Hinsley, Wes; Djaafara, Bimandra A; Wang, Haowei; Fraser, Keith; FitzJohn, Richard G.; Hogan, Alexandra B.; Doohan, Patrick; Ghani, Azra C; Ferguson, Neil; Baguelin, Marc; Cori, Anne

doi:10.1016/s2468-2667(22)00337-1

Cited by 19 publications

(13 citation statements)

References 28 publications

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“…We expanded a previously described 8 – 10 stochastic compartmental SARS-CoV-2 mathematical model and Bayesian evidence synthesis framework, fitting to a range of epidemiological surveillance data streams using particle Markov Chain Monte Carlo 44 , Data range between March 16, 2020 and February 24, 2022 and are aggregated by England NHS (health administration) region. For a full description of the model structure, equations, parameters and fitted data, see online Supplement.…”

Section: Methodsmentioning

confidence: 99%

“…Here we expanded a validated dynamic transmission model using a Bayesian evidence synthesis framework 8 – 10 , and fitted it to comprehensive COVID-19 surveillance data by age and English National Health Service (NHS) regions. Data included the number of positive and negative PCR tests in the community, population-representative infection prevalence surveys, genetic characterisation of a sample of the PCR positive cases, seroprevalence from blood donor residual sera, hospital admissions and deaths, and community deaths (see Fig.…”

Section: Introductionmentioning

confidence: 99%

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Epidemiological drivers of transmissibility and severity of SARS-CoV-2 in England

et al. 2023

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As the SARS-CoV-2 pandemic progressed, distinct variants emerged and dominated in England. These variants, Wildtype, Alpha, Delta, and Omicron were characterized by variations in transmissibility and severity. We used a robust mathematical model and Bayesian inference framework to analyse epidemiological surveillance data from England. We quantified the impact of non-pharmaceutical interventions (NPIs), therapeutics, and vaccination on virus transmission and severity. Each successive variant had a higher intrinsic transmissibility. Omicron (BA.1) had the highest basic reproduction number at 8.3 (95% credible interval (CrI) 7.7-8.8). Varying levels of NPIs were crucial in controlling virus transmission until population immunity accumulated. Immune escape properties of Omicron decreased effective levels of immunity in the population by a third. Furthermore, in contrast to previous studies, we found Alpha had the highest basic infection fatality ratio (2.9%, 95% CrI 2.7-3.2), followed by Delta (2.2%, 95% CrI 2.0–2.4), Wildtype (1.2%, 95% CrI 1.1–1.2), and Omicron (0.7%, 95% CrI 0.6-0.8). Our findings highlight the importance of continued surveillance. Long-term strategies for monitoring and maintaining effective immunity against SARS-CoV-2 are critical to inform the role of NPIs to effectively manage future variants with potentially higher intrinsic transmissibility and severe outcomes.

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Section: Methodsmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Epidemiological drivers of transmissibility and severity of SARS-CoV-2 in England

et al. 2023

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“…Indeed, the introduction of a functional form to model VE over time allows us to compare VE at any time point across different vaccine products, SARS-CoV-2 variants, number of doses, and epidemiologic end points and over relatively longer time horizons. We chose the exponential decay functional form because of its more widespread use and extensive applicability to epidemic models. Alternative functional forms proposed in the literature are the gamma distribution or a linear decay model .…”

Section: Discussionmentioning

confidence: 99%

“…A solid mathematical description of temporal changes in VE may have extensive applications for epidemic models. Various decay functions have been proposed for the COVID-19 VE waning rate in modeling studies 49 , 50 , 51 , 52 , 53 but not within a comprehensive framework comparing the available published evidence.…”

Section: Introductionmentioning

confidence: 99%

Evaluation of Waning of SARS-CoV-2 Vaccine–Induced Immunity

et al. 2023

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ImportanceEstimates of the rate of waning of vaccine effectiveness (VE) against COVID-19 are key to assess population levels of protection and future needs for booster doses to face the resurgence of epidemic waves.ObjectiveTo quantify the progressive waning of VE associated with the Delta and Omicron variants of SARS-CoV-2 by number of received doses.Data SourcesPubMed and Web of Science were searched from the databases’ inception to October 19, 2022, as well as reference lists of eligible articles. Preprints were included.Study SelectionSelected studies for this systematic review and meta-analysis were original articles reporting estimates of VE over time against laboratory-confirmed SARS-CoV-2 infection and symptomatic disease.Data Extraction and SynthesisEstimates of VE at different time points from vaccination were retrieved from original studies. A secondary data analysis was performed to project VE at any time from last dose administration, improving the comparability across different studies and between the 2 considered variants. Pooled estimates were obtained from random-effects meta-analysis.Main Outcomes and MeasuresOutcomes were VE against laboratory-confirmed Omicron or Delta infection and symptomatic disease and half-life and waning rate associated with vaccine-induced protection.ResultsA total of 799 original articles and 149 reviews published in peer-reviewed journals and 35 preprints were identified. Of these, 40 studies were included in the analysis. Pooled estimates of VE of a primary vaccination cycle against laboratory-confirmed Omicron infection and symptomatic disease were both lower than 20% at 6 months from last dose administration. Booster doses restored VE to levels comparable to those acquired soon after the administration of the primary cycle. However, 9 months after booster administration, VE against Omicron was lower than 30% against laboratory-confirmed infection and symptomatic disease. The half-life of VE against symptomatic infection was estimated to be 87 days (95% CI, 67-129 days) for Omicron compared with 316 days (95% CI, 240-470 days) for Delta. Similar waning rates of VE were found for different age segments of the population.Conclusions and RelevanceThese findings suggest that the effectiveness of COVID-19 vaccines against laboratory-confirmed Omicron or Delta infection and symptomatic disease rapidly wanes over time after the primary vaccination cycle and booster dose. These results can inform the design of appropriate targets and timing for future vaccination programs.

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“…[41][42][43][44][45]), for investigating the effect of new variants and waning immunity (e.g. [46][47][48][49][50][51][52][53]. In addition, some online tools were developed for simulating SARS-CoV-2 transmission [54][55][56].…”

Section: Introductionmentioning

confidence: 99%

Covid19Vaxplorer: a free, online, user-friendly COVID-19 Vaccine Allocation Comparison Tool

Trejo

Hung

Matrajt

2023

Preprint

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Background There are many COVID-19 vaccines currently available, however, Lowand middle-income countries (LMIC) still have large proportions of their populations unvaccinated. Decision-makers need to take decisions as of how best to allocate available vaccine (e.g. boosters or primary series vaccination, which age groups to target) but LMIC often lack the resources to undergo quantitative analyses of vaccine allocation, resulting and ad-hoc policies. We developed Covid19Vaxplorer (https://covid19vaxplorer.fredhutch.org/), a free, user-friendly online tool that simulates region-specific COVID-19 epidemics in conjunction with vaccination. Methods We developed an age-structured mathematical model of SARS-CoV-2 transmission and COVID-19 vaccination. The model considers vaccination with up to three different vaccine products, primary series and boosters. We simulate partial immunity derived from waning of natural infection and vaccination. The model is embedded in an an online tool that allows users in 183 regions in the world to compare several vaccination strategies simultaneously, adjusting parameters to their local epidemics, infrastructure and logistics, and reports cumulative number of deaths and epidemic curves. Results We provide two usage examples of Covid19Vaxplorer for vaccine allocation in Haiti and Afghanistan, which had as of Spring 2023 2% and 33% of their populations vaccinated, and show that in these examples, giving primary series vaccinations prevents more deaths than boosters. Covid19Vaxplorer is an online, free, user-friendly tool that facilitates evidence-based decision making for vaccine distribution.

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Quantifying the effect of delaying the second COVID-19 vaccine dose in England: a mathematical modelling study

Cited by 19 publications

References 28 publications

Epidemiological drivers of transmissibility and severity of SARS-CoV-2 in England

Epidemiological drivers of transmissibility and severity of SARS-CoV-2 in England

Evaluation of Waning of SARS-CoV-2 Vaccine–Induced Immunity

Covid19Vaxplorer: a free, online, user-friendly COVID-19 Vaccine Allocation Comparison Tool

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