Potential impact of annual vaccination with reformulated COVID-19 vaccines: lessons from the U.S. 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 Clif 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 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: October 2023

Importance

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.

Objective

To project COVID-19 hospitalizations and deaths from April 2023–April 2025 under two plausible assumptions about immune escape (20% per year and 50% per year) and three possible CDC recommendations for the use of annually reformulated vaccines (no vaccine recommendation, vaccination for those aged 65+, vaccination for all eligible groups).

Design

The COVID-19 Scenario Modeling Hub solicited projections of COVID-19 hospitalization and deaths between April 15, 2023–April 15, 2025 under six scenarios representing the intersection of considered levels of immune escape and vaccination. State and national projections from eight modeling teams were ensembled to produce projections for each scenario.

Setting

The entire United States.

Participants

None.

Exposure

Annually reformulated vaccines assumed to be 65% effective against 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.

Main outcomes and measures

Ensemble estimates of weekly and cumulative COVID-19 hospitalizations and deaths. Expected relative and absolute reductions in hospitalizations and deaths due to vaccination over the projection period.

Results

From April 15, 2023–April 15, 2025, COVID-19 is projected to cause annual epidemics peaking November–January. In the most pessimistic scenario (high immune escape, no vaccination recommendation), we project 2.1 million (90% 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% 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.

Conclusion and Relevance

COVID-19 is projected to be a significant public health threat over the coming two years. Broad vaccination has the potential to substantially reduce the burden of this disease.

Key points

Question

What is the likely impact of COVID-19 from April 2023–April 2025 and to what extent can vaccination reduce hospitalizations and deaths?

Findings

Under plausible assumptions about viral evolution and waning immunity, COVID-19 will likely cause annual epidemics peaking in November–January over the two-year projection period. Though significant, hospitalizations and deaths are unlikely to reach levels seen in previous winters. The projected health impacts of COVID-19 are reduced by 10–20% through moderate use of reformulated vaccines.

Meaning

COVID-19 is projected to remain a significant public health threat. Annual vaccination can reduce morbidity, mortality, and strain on health systems.