Background: Evidence on the humoral and cellular immune responses to SARS-CoV-2 following COVID-19 vaccination in older adults is warranted. Aims: To synthesize and analyze the current evidence on humoral and cellular immune responses to both standard and booster COVID-19 vaccination in individuals aged 60 years and older. Methods: Clinical trials and observational studies were included. Reviews, case series, letters to the editor, and similar publications were excluded. A selective literature search was conducted in the following databases: PubMed, Scopus, EMBASE, and Web of Science. The risk of bias and methodological quality of the included studies were assessed using the Newcastle–Ottawa Scale (NOS) and the Risk of Bias 2.0 (RoB 2) tool. Statistical analysis was conducted using Stata version 18 and Review Manager version 5.4.1. Results: Thirteen studies were included: eleven observational studies and two randomized clinical trials, evaluating humoral and cellular immune responses in 782 older adults. Messenger RNA vaccines were the most administered, particularly Pfizer-BioNTech (76.9%) and Moderna mRNA-1273 (23%). In most cases, immune responses were assessed after the second dose and booster doses. Most studies (61.5%) reported increased IgG titers specific to the SARS-CoV-2 Spike protein, while 23.1% reported a decrease. Regarding cellular immunity, 46.2% of the studies reported low interferon-gamma (IFN-γ) levels post-vaccination, whereas 38.5% showed increases. These findings highlight the need for tailored vaccination strategies to address emerging variants, particularly in vulnerable populations such as older adults. Conclusions: In older adults receiving COVID-19 vaccination, humoral immunity tends to increase, whereas cellular responses are frequently diminished, reflecting age-related immunosenescence that may limit the durability and breadth of protection following vaccination in older adults.

Background and Objectives: The association between SARS-CoV-2 infection, COVID-19 vaccination, and the development of rhabdomyolysis remains unclear. This systematic review aimed to comprehensively synthesize and analyze the available evidence on the occurrence of rhabdomyolysis in the context of SARS-CoV-2 infection and COVID-19 vaccination. Materials and Methods: A literature search was conducted in PubMed, Scopus, EMBASE, and Web of Science. The review followed PRISMA 2020 guidelines, assessing methodological quality. Statistical analyses were performed using STATA v18. Results: A total of 133 patients with rhabdomyolysis associated with SARS-CoV-2 infection were identified from 93 case reports and 7 case series; the median age was 45.5 years (IQR: 24–62), with a predominance of males (72.9%). Additionally, 13 observational studies comprising 818 patients with rhabdomyolysis associated with SARS-CoV-2 infection were included. Among cases associated with SARS-CoV-2 vaccination, 20 patients were identified from 20 case reports; the median age was 52.5 years (IQR: 22.5–76.5), with a predominance of males (75%). These cases were primarily associated with mRNA-based vaccines, particularly Pfizer-BioNTech BNT162b2 (50%) and Moderna (20%), and occurred predominantly after the first and second doses. The most frequent clinical manifestations in both groups were fever, myalgia, and dark urine. Clinical outcomes were favorable in most patients, both among infection-associated cases (72.2%) and vaccination-associated cases (80%). Conclusions: Rhabdomyolysis has been documented during SARS-CoV-2 infection, although its true frequency remains uncertain, whereas cases following COVID-19 vaccination do not establish causality or platform-specific risks.