Impact of Vaccination on Risk of COVID-19–Related Mortality

In this section, we examine how effective COVID-19 vaccines are at protecting against risk of dying from COVID-19. Data are reported from 30 jurisdictions (representing over 70% of the U.S. population and all regions of the country) that actively link immunization and case surveillance data to vital registration data to monitor rates of COVID-19 cases and deaths by vaccination status, including booster doses. Note that rates and rate ratios presented are not adjusted for time since vaccination (i.e., waning immunity), previous infection, underlying conditions, or other factors. For additional information, see COVID Data Tracker, Vaccine Effectiveness and Breakthrough Surveillance.

COVID-19 Vaccines Reduced Risk of COVID-19–Related Mortality

Linked vaccination and mortality data show that despite changes in circulating SARS-CoV-2 variants over time, among older adults aged ≥65 years, unvaccinated individuals continue to have a much greater risk of dying from COVID-19 than individuals vaccinated with at least a primary series. This protective effect of COVID-19 vaccination was seen across all age groups (Figure 9).^{12, 13} In August 2022, the risk of dying from COVID-19 among unvaccinated adults compared with adults who received a primary series was 9 times higher for adults aged 65–79 years and 4 times higher for adults aged ≥80 years. A similar pattern was observed among younger adult age groups in August 2022. Compared with adults who received a primary series in the same age group, the risk of dying from COVID-19 among unvaccinated adults was 3 times higher for adults aged 18–29 years, 5 times higher for adults aged 30–49 years, and 6 times higher for adults aged 50–64 years. Additional booster doses provide added protection. In August 2022, adults aged ≥50 years with at least 2 booster doses had 3 times lower risk of dying from COVID-19 than adults of the same age with one booster dose (Figure 10).

Vaccine effectiveness (VE) studies have shown that receiving 2 or 3 doses of an mRNA COVID-19 vaccine can reduce severe COVID-19 outcomes.^{14, 15} A study that looked at outcomes among hospitalized patients during March–January 2022 found that COVID-19 vaccination was associated with a 90% reduction in risk for severe COVID-19 outcomes, including invasive mechanical ventilation and in-hospital death across all variant periods.¹⁵ Vaccine effectiveness did not differ by age group (18–64 years versus ≥65 years).¹⁵ During the early Omicron period, vaccine effectiveness against invasive mechanical ventilation and in-hospital death was 79% for recipients of 2 doses and 94% for recipients of 3 doses.¹⁵ Vaccinated patients who died were likely to be older, more likely to be immunocompromised, and had more chronic medical conditions compared with unvaccinated case-patients.¹⁵

Receiving a fourth dose of COVID-19 vaccine (second booster) can improve VE against moderate and severe illness. In a study conducted using data from December 2021–June 2022, among adults aged ≥50 years eligible to receive a fourth mRNA vaccine dose, VE for COVID-19–associated emergency department or urgent care encounters during the later Omicron period (BA.2/BA.2.12.1) was 32% at ≥120 days after the third dose (median interval = 170 days) but increased to 66% ≥7 days after the fourth dose (median interval = 28 days).¹⁶ VE against COVID-19–associated hospitalization was 55% ≥120 days after the third dose but increased to 80% ≥7 days after the fourth dose.¹⁶ Follow-up time after the fourth dose was limited.¹⁶