Impact of SARS-CoV-2 vaccination of children ages 5-11 years on COVID-19 disease burden and resilience to new variants in the United States, November 2021-March 2022: a multi-model study
Authors: Borchering Rebecca K. , Mullany Luke C. , Howerton Emily , Chinazzi Matteo , Smith Claire P. , Qin Michelle , Reich Nicholas G. , Contamin Lucie , Levander John , Kerr Jessica , Espino J , Hochheiser Harry , Lovett Kaitlin , Kinsey Matt , Tallaksen Kate , Wilson Shelby , Shin Lauren , Lemaitre Joseph C. , Hulse Juan Dent , Kaminsky Joshua , Lee Elizabeth C. , Davis Jessica T. , Mu Kunpeng , Xiong Xinyue , Piontti Ana Pastore y , Vespignani Alessandro , Srivastava Ajitesh , Porebski Przemyslaw , Venkatramanan Srini , Adiga Aniruddha , Lewis Bryan , Klahn Brian , Outten Joseph , Hurt Benjamin , Chen Jiangzhuo , Mortveit Henning , Wilson Amanda , Marathe Madhav , Hoops Stefan , Bhattacharya Parantapa , Machi Dustin , Chen Shi , Paul Rajib , Janies Daniel , Thill Jean-Claude , Galanti Marta , Yamana Teresa , Pei Sen , Shaman Jeffrey , Espana Guido , Cavany Sean , Moore Sean , Perkins Alex , Healy Jessica M. , Slayton Rachel B. , Johansson Michael A. , Biggerstaff Matthew , Shea Katriona , Truelove Shaun A. , Runge Michael C. , Viboud Cécile , Lessler Justin 
Published: March 2022

Background

SARS-CoV-2 vaccination of persons aged 12 years and older has reduced disease burden in the United States. The COVID-19 Scenario Modeling Hub convened multiple modeling teams in September 2021 to project the impact of expanding vaccine administration to children 5-11 years old on anticipated COVID-19 burden and resilience against variant strains.

Methods

Nine modeling teams contributed state- and national-level projections for weekly counts of cases, hospitalizations, and deaths in the United States for the period September 12, 2021 to March 12, 2022. Four scenarios covered all combinations of: 1) presence vs. absence of vaccination of children ages 5-11 years starting on November 1, 2021; and 2) continued dominance of the Delta variant vs. emergence of a hypothetical more transmissible variant on November 15, 2021. Individual team projections were combined using linear pooling. The effect of childhood vaccination on overall and age-specific outcomes was estimated by meta-analysis approaches.

Findings

Absent a new variant, COVID-19 cases, hospitalizations, and deaths among all ages were projected to decrease nationally through mid-March 2022. Under a set of specific assumptions, models projected that vaccination of children 5-11 years old was associated with reductions in all-age cumulative cases (7.2%, mean incidence ratio [IR] 0.928, 95% confidence interval [CI] 0.880-0.977), hospitalizations (8.7%, mean IR 0.913, 95% CI 0.834-0.992), and deaths (9.2%, mean IR 0.908, 95% CI 0.797-1.020) compared with scenarios where children were not vaccinated. This projected effect of vaccinating children 5-11 years old increased in the presence of a more transmissible variant, assuming no change in vaccine effectiveness by variant. Larger relative reductions in cumulative cases, hospitalizations, and deaths were observed for children than for the entire U.S. population. Substantial state-level variation was projected in epidemic trajectories, vaccine benefits, and variant impacts.

Conclusions

Results from this multi-model aggregation study suggest that, under a specific set of scenario assumptions, expanding vaccination to children 5-11 years old would provide measurable direct benefits to this age group and indirect benefits to the all-age U.S. population, including resilience to more transmissible variants.