Potential impact of annual vaccination with reformulated COVID-19 vaccines: Lessons from the US COVID-19 scenario modeling hub
Authors: Jung Sung-mok , Loo Sara L. , Howerton Emily , Contamin Lucie , Smith Claire P. , Carcelén Erica C. , Yan Katie , Bents Samantha J. , Levander John , Espino Jessi , Lemaitre Joseph C. , Sato Koji , McKee Clifton D. , Hill Alison L. , Chinazzi Matteo , Davis Jessica T. , Mu Kunpeng , Vespignani Alessandro , Rosenstrom Erik T. , Rodriguez-Cartes Sebastian A. , Ivy Julie S. , Mayorga Maria E. , Swann Julie L. , España Guido , Cavany Sean , Moore Sean M. , Perkins T. Alex , Chen Shi , Paul Rajib , Janies Daniel , Thill Jean-Claude , Srivastava Ajitesh , Aawar Majd Al , Bi Kaiming , Bandekar Shraddha Ramdas , Bouchnita Anass , Fox Spencer J. , Meyers Lauren Ancel , Porebski Przemyslaw , Venkatramanan Srini , Adiga Aniruddha , Hurt Benjamin , Klahn Brian , Outten Joseph , Chen Jiangzhuo , Mortveit Henning , Wilson Amanda , Hoops Stefan , Bhattacharya Parantapa , Machi Dustin , Vullikanti Anil , Lewis Bryan , Marathe Madhav , Hochheiser Harry , Runge Michael C. , Shea Katriona , Truelove Shaun , Viboud Cécile , Lessler Justin 
Published: April 2024

Background
Coronavirus Disease 2019 (COVID-19) continues to cause significant hospitalizations and deaths in the United States. Its continued burden and the impact of annually reformulated vaccines remain unclear. Here, we present projections of COVID-19 hospitalizations and deaths in the United States for the next 2 years under 2 plausible assumptions about immune escape (20% per year and 50% per year) and 3 possible CDC recommendations for the use of annually reformulated vaccines (no recommendation, vaccination for those aged 65 years and over, vaccination for all eligible age groups based on FDA approval).

Methods and findings
The COVID-19 Scenario Modeling Hub solicited projections of COVID-19 hospitalization and deaths between April 15, 2023 and April 15, 2025 under 6 scenarios representing the intersection of considered levels of immune escape and vaccination. Annually reformulated vaccines are assumed to be 65% effective against symptomatic infection with strains circulating on June 15 of each year and to become available on September 1. Age- and state-specific coverage in recommended groups was assumed to match that seen for the first (fall 2021) COVID-19 booster. State and national projections from 8 modeling teams were ensembled to produce projections for each scenario and expected reductions in disease outcomes due to vaccination over the projection period.
From April 15, 2023 to April 15, 2025, COVID-19 is projected to cause annual epidemics peaking November to January. In the most pessimistic scenario (high immune escape, no vaccination recommendation), we project 2.1 million (90% projection interval (PI) [1,438,000, 4,270,000]) hospitalizations and 209,000 (90% PI [139,000, 461,000]) deaths, exceeding pre-pandemic mortality of influenza and pneumonia. In high immune escape scenarios, vaccination of those aged 65+ results in 230,000 (95% confidence interval (CI) [104,000, 355,000]) fewer hospitalizations and 33,000 (95% CI [12,000, 54,000]) fewer deaths, while vaccination of all eligible individuals results in 431,000 (95% CI: 264,000–598,000) fewer hospitalizations and 49,000 (95% CI [29,000, 69,000]) fewer deaths.

Conclusions
COVID-19 is projected to be a significant public health threat over the coming 2 years. Broad vaccination has the potential to substantially reduce the burden of this disease, saving tens of thousands of lives each year.