The Efficacy of SARS-CoV-2 Vaccination in the Elderly: A Systemic Review and Meta-analysis

Abstract

Background Given the reduced immune response to vaccines in older populations, this study aimed to evaluate the efficacy of COVID-19 vaccinations and its impact on breakthrough infection, hospital admission, and mortality in the elderly. Methods We carried out a systemic review and meta-analysis where MEDLINE, Web of Science, EMBASE, ClinicalTrials.gov, and Cochrane Central Register for Controlled Trials were queried to identify relevant literature. We included randomized controlled trials (RCTs), non-randomized trials, prospective, observational cohort, and case–control studies assessing breakthrough infection, hospital admission, and mortality after coronavirus 2 (SARS-CoV-2) vaccination in the elderly (≥ 60 years old). Results Overall, 26 studies were included in this meta-analysis. Compared with the unvaccinated group, the vaccinated group showed a decreased risk of SARS-CoV-2 infection after 28–34 (relative risk [RR] = 0.42, 95% confidence interval [CI] 0.37–0.49) and 35–60 days (RR = 0.49, 95% CI 0.37–0.62). There was a step-wise increase in efficacy with additional doses with the two-dose group experiencing decreased risk of breakthrough infection (RR = 0.37, 95% CI 0.32–0.42), hospital admissions (RR = 0.25, 95% CI 0.14–0.45), disease severity (RR = 0.38, 95% CI 0.20–0.70), and mortality (RR = 0.21, 95% CI 0.14–0.32) compared with those receiving one or no doses. Similarly three-dose and four-dose vaccine groups also showed a decreased risk of breakthrough infection (3-dose: RR = 0.14, 95% CI 0.10–0.20; 4-dose RR = 0.46, 95% CI 0.4–0.53), hospital admissions (3-dose: RR = 0.11, 95% CI 0.07–0.17; 4-dose: RR = 0.42, 95% CI 0.32–0.55), and all-cause mortality (3-dose: RR = 0.10, 95% CI 0.02–0.48; 4-dose: RR = 0.48, 95% CI 0.28–0.84) Subgroup analysis found that protection against mortality for vaccinated vs. unvaccinated groups was similar by age (60–79 years: RR = 0.59; 95% CI, 0.47–0.74; ≥ 80 years: RR = 0.76; 95% CI, 0.59–0.98) and gender (female: RR = 0.66; 95% CI, 0.50–0.87, male: (RR = 0.58; 95% CI, 0.44–0.76), and comorbid cardiovascular disease (CVD) (RR = 0.69; 95% CI, 0.52–0.92) or diabetes (DM) (RR = 0.59; 95% CI, 0.39–0.89. Conclusions Our pooled results showed that SARS-CoV-2 vaccines administered to the elderly is effective in preventing prevent breakthrough infection, hospitalization, severity, and death. What’s more, increasing number of vaccine doses is becoming increasingly effective. Supplementary Information The online version contains supplementary material available at 10.1007/s11606-023-08254-9.

COVID-19 Vaccination Effectiveness in the General Population of an Italian Province: Two Years of Follow-Up

“…The absolute risk differences were 19% for COVID-19-related deaths and 22% for severe COVID-19 cases. In this age class, due to the combination of a highly effective vaccine (>80% in our study as well as in other studies [37,38]) and a disease with such a high case-fatality rate, the impact of vaccination was massive, and the prolonged follow-up provides a strong confirmation of the correctness of the public health entities which prioritized immunization among the interventions to control the pandemics [39]. As regards the younger subjects (<30 years of age), in line with available evidence on the lower severity of SARS-CoV-2 infection among this subset of the population, we observed a low absolute frequency of severe COVID-19 and related deaths in this age class (2 out 1000 and 2 out 10,000, respectively) [40].…”

“…Given their higher risk of severe COVID-19-related outcomes [ 34 , 35 , 36 ], the finding that the highest absolute benefit of vaccination was observed among the elderly was clearly expected [ 37 , 38 ]. The magnitude of such benefit, however, after two years of follow-up, was impressive: once infected, more than one-fifth of the unvaccinated older subjects died, as compared to one out of twenty of those who received a booster dose.…”

Vaccines for the Elderly and Vaccination Programs in Europe and the United States

“…Mattiuzi et al compared data from approximately 2.4 million individuals over 80 years of age who completed the initial COVID-19 vaccination and 1.5 million who received booster shots and concluded that boosting resulted in an 75% reduction in risk for infection, 82% reduced risk for hospitalization, and 81% reduced mortality risk [ 187 ]. Yang et al, however, found that when compared to unvaccinated individuals over 80 years of age, vaccination does not seem to reduce mortality [ 188 ]. Vaccine efficacy in elders was nonetheless highly associated with booster shots, as evident by the stepwise increase in vaccine efficacy following three or four vaccine doses [ 188 ].…”

“…Yang et al, however, found that when compared to unvaccinated individuals over 80 years of age, vaccination does not seem to reduce mortality [ 188 ]. Vaccine efficacy in elders was nonetheless highly associated with booster shots, as evident by the stepwise increase in vaccine efficacy following three or four vaccine doses [ 188 ]. Li et al analyzed data from 9 and 21 studies to determine efficacy and immunogenicity, respectively, of COVID-19 vaccines in older individuals aged over 55.…”