Effectiveness of COVID-19 Booster Vaccination

­Booster vaccination against COVID-19 was found to reduce risk of COVID-19-related death regardless of immune status, according to the results of a study presented at the 2022 Conference for Antiretrovirals and Opportunistic Infections (CROI).

The US National COVID Cohort Collaborative used data from 50 sites to estimate the effectiveness of booster vaccination compared with that of full vaccination (defined as 2 doses of mRNA or 1 dose of Janssen vaccine).

At each month after full vaccination, the researchers created comparable cohorts of patients whose booster propensity‑score was matched to those without boosters by age, sex, race/ethnicity, comorbidities, region, prior COVID-19 infection, and calendar month of full vaccination. They then evaluated the efficacy of a booster among patients with and without immunosuppression or compromise (ISC) from conditions such as HIV infection, transplantation, autoimmune disease, and cancer. They used Cox regression models to determine the chance of having a breakthrough infection, which was defined as a COVID-19 diagnosis occurring after the final dose of vaccine. They used logistic regression models to compare risk of death within 45 days after such an infection in the boosted group vs the matched, non-boosted group.

As a result, they found that booster vaccination was associated with less chance of having a breakthrough infection (P < .01). In those without ISC, the efficacy of booster vaccination ranged from 46% when the booster was received 1 to 4 months after full vaccination to 83% when the booster was received 7 months after full vaccination. By comparison, booster vaccine efficacy was lower (ranging from 43% to 65%) in those with ISC.

However, compared with fully vaccinated patients who had not received a booster, those who received a booster had an 83% reduced risk of COVID-19-related death independent of immune status, comorbidities, demographic characteristics, region, prior COVID‑19 infection, and time of full vaccination.

“A booster dose of COVID-19 has high effectiveness in reducing breakthrough infection risk among all fully vaccinated individuals, though only moderate effectiveness among ISC patients,” the researchers concluded. “Nonetheless, booster vaccination significantly reduced risk for COVID‑19 related death regardless of ISC status.”


—Ellen Kurek



Sun J, Zheng Q,  Anzalone A,  et al. COVID-19 booster vaccine effectiveness in people with and without immune dysfunction. Paper presented at: Conference on Retroviruses and Opportunistic Infections, February 12–16 and 22–24, 2022; Virtual. Accessed February 21, 2022.