In older adults, the rate of hospitalization and mortality is similar for respiratory syncytial virus (RSV) and influenza, thus highlighting the importance of an RSV vaccine for this at-risk population. These findings were reported in a systematic review and meta-analysis published in the journal Vaccines (Basel).
Development of a vaccine to prevent severe RSV-associated illness is an unmet need. More than 30 RSV vaccine prevention candidates are in clinical development and use a variety of approaches. According to study authors, “[A] phase 3 trial reported that a single dose of an adjuvant vaccine was highly efficacious against RSV-confirmed lower respiratory tract diseases and RSV-confirmed acute respiratory infections in older adults, regardless of RSV disease severity, RSV subtype, baseline comorbidity and presence of frailty.”
Although the epidemiologic importance of influenza in the elderly population has been widely recognized, RSV was seen as an infection that most seriously affected children and has only recently gained attention for its potential to cause harm among middle-aged and elderly adults. Researchers therefore conducted a literature review and meta-analysis to compare rates of hospitalization and death among elderly persons with RSV and those with influenza.
The researchers searched literature across several databases through June 15, 2022, for studies that reported incidence rates, as well as the cumulative incidence of hospitalization and mortality, for influenza and RSV in older patients. Using the PICOS (Population, Intervention, Comparison, Outcomes, and Study) systematic review framework, the investigators considered prospective and retrospective studies (including conference abstracts with sufficient data) of older participants (≥60 years of age) affected by RSV as well as comparative populations comprising either healthy people or individuals with influenza.
The primary outcomes were incidence rates of hospitalization and mortality. The incidence could be reported either as overall cumulative incidence or as standardized incidence rates with 95% CIs. All data were reported per 100,000 person-years for hospitalization and per 1000 person-years for mortality.
Investigators ultimately chose 16 studies comprising 762,084 older participants for meta-analysis. Analysis results showed that when compared with older patients with influenza, individuals of the same age with RSV did not demonstrate a significantly different risk for hospitalization (risk rate [RR] for cumulative incidence, 0.93; 95% CI, 0.53-1.62; P =.80; I2 =0%; 5 studies; ) or for mortality (RR for cumulative incidence, 1.19; 95% CI, 0.98-1.45; P =.08; I2 =0%; 4 studies). Studies reporting mean differences (MD) in incidence rate between influenza and RSV also did not indicate significantly different risks with respect to mortality (MD per 1000, 15; 95% CI, -133 to 162; P =.85; I2 =0%; 2 studies) or hospitalization (MD per 100,000 person-years, -262; 95% CI, -755 to 229; I2 = 99%; 10 studies), although the hospitalization outcome was characterized by high heterogeneity. Reviewers further noted that studies were good and showed no evident publication bias.
Limitations of this analysis include the high heterogeneity of some outcomes data; potential for bias due to the retrospective design of approximately half of the studies evaluated; and a lack of generalizability of findings due to a lack of studies involving Asian countries.
The study authors concluded that “Since RSV is highly prevalent in older people and associated with negative outcomes, our systematic review supports the need of increasing awareness before vaccine availability.” They further noted that “Future studies confirming our findings in the light of public health interventions are needed.”
Disclosure: None of the study authors has declared affiliations with biotech, pharmaceutical, and/or device companies.
Maggi S, Veronese N, Burgio M, et al. Rate of hospitalizations and mortality of respiratory syncytial virus infection compared to influenza in older people: a systematic review and meta-analysis. Vaccines (Basel). 2022;10(12):2092.