Less common than COVID-19, but hits harder, CDC study reveals

In a recent study published in the Centre for Disease Control and Prevention’s (CDC’s) Morbidity and Mortality Weekly Report (MMWR), researchers compared the prevalence and disease severity of respiratory syncytial virus (RSV) infections with other common respiratory ailments, notably coronavirus disease 2019 (COVID-19) and influenza. A multivariate logistic regression analysis of data from almost 5,800 Americans aged 60+ years revealed that, while not as infectious, RSV infections result in much more severe clinical outcomes than either COVID-19 or influenza. The findings from this report come in tandem with- and help inform the CDC’s Advisory Committee on Immunization Practices recommending RSV vaccination, especially for older Americans.

Study: Disease Severity of Respiratory Syncytial Virus Compared with COVID-19 and Influenza Among Hospitalized Adults Aged ≥60 Years — IVY Network, 20 U.S. States, February 2022–May 2023. Image Credit: eggeegg / Shutterstock

Respiratory syncytial virus

The respiratory syncytial virus (RSV), also called the human orthopneumovirus, is a negative-sense, single-stranded RNA virus that infects the respiratory tract in humans. RSV infects humans of all age groups, with differing clinical outcomes based on patient age – RSV is a common cause of respiratory hospitalizations in infants, results in usually mild, cold-like symptoms in adults, and potentially deadly pneumonia-like symptoms in the elderly and immunocompromised individuals.

RSV is a contagious pathogen, with transmission occurring mainly through infection of victims’ eyes or nasal passages. Hitherto, infection treatment has been primarily supportive, involving oxygen therapy for mild cases and high-flow nasal cannula (HFNC) or noninvasive ventilation (NIV) for more advanced infections. In life-threatening scenarios, intensive care unit (ICU) admission and invasive mechanical ventilation (IMV) are employed. Until recently, however, antiviral therapy was restricted to children (Ribavirin), with no vaccines approved for human use. In May 2023, the US Food and Drug Administration (FDA) approved the first RSV vaccines, Arexvy (developed by GlaxoSmithKline [GSK] plc) and Abrysvo (Pfizer).

A month later, on June 21, 2023, the CDC began recommending RSV vaccinations to Americans aged 60 years and above since they historically experience the most severe RSV infections with the poorest clinical outcomes. However, hitherto, few studies have investigated the American statistics of RSV in the elderly, necessitating research into the cons of RSV, which vaccination would help circumvent. These studies would help both clinicians and prospective vaccine recipients make informed decisions about whether vaccination is right for them.

About the study

In the present study, researchers aimed to compare and contrast the prevalence and disease severity of RSV, COVID-19, and influenza. Their disease severity outcome measures comprised standard flow oxygen therapy (<30 L/minute), HFNC or NIV, ICU admissions, and IMV or death.

Between February 1, 2022, and May 31, 2023, data from adults over the age of 60 presenting respiratory ailments clinically confirmed as being RSV, COVID-19, or influenza were collected and compiled. The sample cohort focused on patients admitted to any of the 25 American hospitals (20 US states) participating in the Investigating Respiratory Viruses in the Acutely Ill (IVY) Network. Demographic and clinical data were obtained from interviews and medical records, including clinical outcomes by day 28 following hospital admission.

Individuals who presented multiple coinfections, missing medical data, or inconclusive diagnostic results were excluded. Clinical outcomes were compared using multivariable logistic regression models. To reduce confounding results and avoid bias, statistical models were corrected for demographic (age, sex, race, and ethnicity), clinical (number of organ systems affected), and geographic data.

“This activity was reviewed by CDC, deemed not research, and was conducted consistent with applicable federal law and CDC policy.”

Study findings

Data collected initially comprised 6,061 elderly, of which 277 were excluded due to incomplete records. Analyses revealed that, of the remaining 5,784 patients included, 5.3% (304 individuals) were admitted due to RSV, 81.8% (4,734) due to COVID-19, and 12.9% (746) due to influenza, highlighting the low overall prevalence of RSV amongst elderly Americans. Notably, while RSV and influenza prevalence showed a strong association with seasonality, COVID-19 prevalence remained high year-long.

The median age of the included participants remained non-significant – RSV was found to be 72 years, COVID-19 was shown to be 74 years, and influenza was 71 years. While this did not reveal age-specific differences between the infection risk of the diseases under study, it did highlight the age category at highest risk from respiratory infections.

“Patients hospitalized with RSV had chronic medical conditions associated with a median of two organ systems, a finding similar to that for patients hospitalized with COVID-19 or influenza. Among the 5,784 included patients, 4,713 (81.5%) had received ≥1 dose of original (ancestral) monovalent or bivalent (ancestral and BA.4/5) COVID-19 vaccine, and 2,795 (48.3%) had received seasonal influenza vaccination.”

Adjusted multivariate analyses revealed that RSV patients presented significantly more severe disease outcomes than either COVID-19 or influenza and were hence more likely to require standard flow oxygen, HFNC or NIV, or ICU admissions. Odds ratios of IMV or death from RSV were substantially higher for RSV when compared to influenza but did not differ appreciably between RSV and COVID-19.

Conclusions

The present study compared disease prevalence and severity between RSV, COVID-19, and influenza and highlights that while significantly less common, RSV infections are much more clinically severe than the other 2 diseases.

“The high RSV disease severity observed among older adults in this analysis is important to guide decision-making for RSV vaccination in this population. Although neither of the two clinical trials that led to Food and Drug Administration (FDA) approval of RSV vaccines for older adults was powered to assess protection of RSV vaccination against hospitalization in adults aged ≥60 years, both trials showed moderate to high efficacy of RSV vaccination against lower respiratory tract disease, which is in the causal pathway leading to severe disease (8,9). Although additional studies are needed to assess protection of these vaccines against severe respiratory disease in older adults, RSV vaccination has the potential to prevent severe respiratory disease and is currently the only approved prevention product available for older adults.”

How Are Older Adults Impacted By RSV?

How Are Older Adults Impacted By RSV?Play