A systematic review and meta-analysis of the effectiveness and safety of COVID-19 vaccination in older adults

Abstract

In the coronavirus disease 2019 (COVID-19) pandemic, vaccinations were essential in preventing COVID-19 infections and related mortality in older adults. The objectives of this study were to evaluate the effectiveness and safety of the COVID-19 vaccines in older adults. We systematically searched the electronic bibliographic databases of PubMed, Web of Science, Embase, Cochrane Library, ClinicalTrials.gov, Research Square, and OpenGrey, as well as other sources of gray literature, for studies published between January 1, 2020, and October 1, 2022. We retrieved 22 randomized controlled trials (RCTs), with a total of 3,404,696 older adults (aged over 60 years) participating, that were included in the meta-analysis. No significant publication bias was found. In the cumulative meta-analysis, we found that the COVID-19 vaccines were effective in preventing severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) infection (OR = 0.38, 95% CI = 0.23–0.65, p = 0.0004) and in reducing the number of COVID-19-related deaths (OR = 0.16, 95% CI = 0.10–0.25, p < 0.00001) in elderly people. Antibody seroconversion (AS) and geometric mean titer (GMT) levels significantly increased in vaccinated older adults [OR = 24.42, 95% CI = 19.29–30.92; standardized mean difference (SMD) = 0.92, 95% CI = 0.64–1.20, respectively]. However, local and systemic adverse events after COVID-19 vaccine administration were found in older adults (OR = 2.57, 95% CI = 1.83–3.62, p < 0.00001). Although vaccination might induce certain adverse reactions in the elderly population, the available evidence showed that the COVID-19 vaccines are effective and tolerated, as shown by the decrease in COVID-19-related deaths in older adults. It needs to be made abundantly clear to elderly people that the advantages of vaccination far outweigh any potential risks. Therefore, COVID-19 vaccination should be considered as the recommended strategy for the control of this disease by preventing SARS-CoV-2 infection and related deaths in older adults. More RCTs are needed to increase the certainty of the evidence and to verify our conclusions.Systematic review registrationhttps://www.crd.york.ac.uk/prospero/display_record.php?ID=CRD42022319698, identifier CRD42022319698.

Changes in the innate immune response to SARS-CoV-2 with advancing age in humans

“…SARS-CoV-2 infection is more severe and prevalent as we age [ 41 – 43 ]. The hospitalization and mortality rates are higher in elderly individuals despite vaccination [ 9 , 10 ]. Several studies have investigated the underlying immune mechanisms, including innate immune mechanisms [ 44 , 45 ].…”

“…Comorbidities including diabetes, hypertension, and heart disease add further to the risk [ 2 , 5 – 8 ]. Though vaccination has significantly reduced the risk of COVID complications and hospitalization, according to CDC older adults still accounted for 63% of all COVID-related hospitalizations and approximately 90% of deaths in 2023 in the United States [ 9 , 10 ]. Data from the COVID-19–Associated Hospitalization Surveillance Network (COVID-NET) also indicates that hospitalization rates were higher in subjects 65 years and older in 2023 [ 9 ].…”

Incidence and Nature of Adverse Events Following COVID-19 Second Boosters: Insights from Taiwan's Universal Vaccination Strategy

“…2 side events following COVID-19 vaccination, with particular emphasis on specific groups such as the elderly [13], pregnant women [2,14,15], and those with pre-existing medical conditions. Furthermore, retrospective reports have highlighted vaccine-related neurological adverse events [1,7,16] and cardiovascular complications [3,17,18].…”

“…The risk of AE could be repeated, upon subsequent administrations of the same vaccine. Given the variety of COVID-19 vaccines available, each based on different technological platforms such as mRNA and non-replicating viral vectors, potential mechanisms for this could involve immunological responses such as hypersensitivity or immune sensitization, especially relevant in the context of repeated exposures to vaccine antigens [3,13,29]. Moreover, the risk of AE could be cumulative potentially due to cumulative immunological effects or other underlying biological factors.…”

Incidence and Nature of Short-Term Adverse Events following COVID-19 Second Boosters: Insights from Taiwan’s Universal Vaccination Strategy

“…Recent studies from large pharmacovigilance databases indicate substantial variability in adverse event incidence rates, emphasizing the need for context-specific analysis in vaccine safety surveillance to maintain public trust and inform future vaccination strategies [ 8 , 9 , 10 , 11 , 12 ]. There are numerous reports of adverse events following COVID-19 vaccination, with particular emphasis on specific groups such as the elderly [ 13 ], pregnant women [ 2 , 14 , 15 ], and those with pre-existing medical conditions. Furthermore, retrospective reports have highlighted vaccine-related neurological adverse events [ 1 , 7 , 16 ] and cardiovascular complications [ 3 , 17 , 18 ].…”