Reviewing the CDC 2024-2025 respiratory virus season outlook

Last week, the CDC released its 2024-2025 respiratory disease season outlook, indicating that the upcoming fall and winter respiratory virus season will produce similar or lower peak numbers of hospitalizations.

The organization's outlook focused on three primary respiratory infections, including COVID-19, influenza and respiratory syncytial virus (RSV). Predictions about the upcoming respiratory virus season were formed using input from experts, historical data, and scenario modeling from the Center for Forecasting and Outbreak Analytics.

While the organization acknowledges the inherent uncertainty associated with longitudinal predictions, it offers insights and justifications for its forecasts in the upcoming seasons.

First, the public health organization examined the combined peak hospitalization burden of COVID-19, influenza and RSV. Analysts made predictions for the 20204-2025 season based on three scenarios relative to the 2023:2024 season. A similar peak would be defined as a combined peak hospitalization burden in 2024-2025 within 20% (either greater or lower) of the combined peak hospitalization burden in 2023-2024. A lower peak would be a significantly lower combined peak hospitalization burden in 2024-2025 (20% lower or more). Finally, a higher peak would be 20% higher or more than the combined peak hospitalization burden in 2023-2024.

According to the data presented in the outlook report, CDC experts predict that there is a roughly 80% chance that the combined peak hospitalization burden of COVID-19, influenza, and RSV will be similar to or lower than last season. There is a 54% probability of a similar peak and a 28% probability of a lower peak. The data estimates an 18% chance that the peak will be higher this season.

Looking at independent data for each condition, the CDC depicts two scenarios for COVID-19. In the first scenario, the summer COVID-19 hospitalization rate does not peak before the start of respiratory virus season. In this case, the CDC anticipates that the fall and winter COVID-19 hospitalization rates will peak at 7.2-9.7 hospitalizations per 100,000 in late December.

However, the second scenario paints a more promising picture, in which the summer COVID-19 hospitalization rates peak before the respiratory season begins. In this case, the CDC estimates that the respiratory season wave could be smaller, peaking at 4.2-58 hospitalizations per 100,000 in mid-January.

Regarding influenza, the CDC predicts a peak hospitalization rate similar to or lower than 8.9 weekly laboratory-confirmed hospitalizations per 100,000, which was the peak in the 2023-2024 respiratory disease season. These predictions are based mainly on estimates for the influenza vaccine this season. For example, experts hypothesize that the annual influenza vaccine will be 33% to 50% effective at protecting against infection. Additionally, estimated vaccine uptake for adults 18 and older ranges from 42% to 44%.

Finally, focusing on RSV, the CDC estimates similar or lower rates than the 2023-2024 season level of 4.2 weekly laboratory-confirmed hospitalizations per 100,000. Although RSV vaccines are currently only recommended for vulnerable populations, such as the elderly, infants and pregnant individuals, the CDC predicts that vaccine uptake will contribute to similar or lower hospitalization rates.

Although the availability of prevention tools and current viral trends have informed the CDC's prediction that 2024-2025 hospitalization peaks will be similar to or lower than the previous year, certain factors might contribute to higher rates. For example, new strains of COVID-19 or the predominance of different influenza subtypes could skew predictions. Additionally, lower vaccine uptake or effectiveness could contribute to higher rates.

Despite these predictions, following the appropriate public health guidelines and getting vaccinated will be critical to protecting against respiratory viruses this season.

Veronica Salib has covered news related to the pharmaceutical and life sciences industry since 2022.