Association of 2024–2025 Covid-19 Vaccine with Covid-19 Outcomes in U.S. Veterans (2025)
The Covid-19 vaccine was associated with an estimated vaccine effectiveness ranging from 29% against emergency department visits to 39% against hospitalization and 64% against death, findings that closely mirror the immunologic gradient observed in trials and mechanistic studies.
Global Estimates of Lives and Life-Years Saved by COVID-19 Vaccination During 2020-2024 (2025)
The overall benefit corresponds to 1 death averted per 5400 vaccine doses (sensitivity range, 1 death averted per 3500 to 9300 vaccine doses) and 1 life-year saved per 900 (sensitivity range, 600 to 1800) vaccine doses.
Estimated 2023-2024 COVID-19 Vaccine Effectiveness in Adults (2025).
In this case-control study of medically attended COVID-19–like illness encounters from September 21, 2023, to August 22, 2024, vaccination with the 2023-2024 COVID-19 vaccines provided additional effectiveness against COVID-19–associated ED and UC encounters, hospitalizations, and critical illness among adults 18 years or older compared with no receipt of the 2023-2024 COVID-19 vaccine. As found with earlier formulations of COVID-19 vaccines, VE waned over time but appeared highest and most durable against critical illness.11–13 In a combined season analysis, a second bivalent or 2023 to 2024 dose in adults 65 years or older appeared to provide some additional effectiveness beyond a single dose. (
This retrospective cohort study provides evidence of significant protection elicited by mRNA-1273.815 against COVID-19-related hospitalization and medically attended COVID-19 through more than 3 months post-vaccination among adults active in the insurance system and with the healthcare system in the US, featuring a median of nearly 3 months of follow-up. Notably, this protection was consistently observed across various subgroups, including older adults and immunocompromised patients, and those with other specific underlying medical conditions that may have increased their risk of severe COVID-19.
In this real-world study involving > 1.2 million vaccinated patients, the mRNA-1273.815 vaccine (2023–2024 Omicron XBB.1.5-containing mRNA COVID-19 vaccine) demonstrated significant protection against COVID-19-related hospitalizations and medically attended COVID-19 in an insured adult US population. These findings are consistent with effectiveness estimates of 2023–2024 updated COVID-19 vaccines overall, especially demonstrating effectiveness across varied subpopulations and over time, reinforcing the continued role of updated COVID-19 vaccinations in protection against COVID-19-related outcomes.
Our study showed that fully vaccinated patients had more mild disease, fewer complications during their hospital stay, and a lower-case fatality rate compared to partially vaccinated and unvaccinated patients…Patients who were fully vaccinated had more comorbidities, which are known risk factors for breakthrough infections and severe disease in general. Our cohort of fully vaccinated patients were more likely to be white and had a higher mean age. They also were more likely to have hypertension, heart failure, renal disease, and malignancy compared to unvaccinated and partially vaccinated patients. [ie, in spite of more comorbidities, vaccinated patients did better than unvaccinated ones].
Patients who were unvaccinated or partially vaccinated had more in-hospital complications, severe disease, and death as compared to fully vaccinated patients. Factors associated with severity include advanced age, obesity, low serum albumin, and steroid use.
COVID-19 Vaccination and Incidence of Pediatric SARS-CoV-2 Infection and Hospitalization (2024)
We provide evidence that California’s pediatric COVID-19 immunization program averted 376 085 (95% PI, 348 355-417 328) reported cases and 273 (95% PI, 77-605) hospitalizations among children aged 6 months to 15 years during the 4 to 7 months following vaccine availability. This represents a reduction of 26.3% of the number of cases that would have been seen in this population absent the vaccine.
The cumulative effect of vaccination at the population level may be meaningful even if individual vaccine effectiveness is low. While influenza vaccine effectiveness was estimated at 29% in 2017-2018,28 it was estimated that widespread vaccination averted more than 3.1 million cases of influenza in the US.
COVID-19-associated hospitalization were approximately 10.5 times higher in unvaccinated adults compared with adults vaccinated with a primary series and a booster dose during January to April 2022, when the Omicron variant was predominant. This suggests that COVID-19 vaccines continue to effectively prevent hospitalizations in all adults.
