The efficacy of the annual flu vaccine varies year to year
With flu season quickly approaching here in the U.S., a report from the Centers for Disease Control and Prevention (CDC) has revealed new information on this years flu vaccine.
Each year, the CDC looks at flu season data from South America, as the flu season there occurs earlier than in the States.
This year, that data showed that the yearly flu shot was 34.5% effective at preventing flu-related hospitalizations in Argentina, Chile, Brazil, Paraguay, and Uruguay. For reference, in 2023, data from the same countries showed that the flu shot had a 52% efficacy at preventing hospitalizations.
Interim estimates of influenza vaccine effectiveness (VE) from Southern Hemisphere countries can provide early information about the protective effects of vaccination and help guide Northern Hemisphere countries in advance of their season, the CDC wrote in its Morbidity and Mortality Weekly Report.
A look at the data
To get a better idea of what to expect from the flu shot this year, researchers at the CDC looked at patient data from 2,535 hospitals 30 in Argentina, 2,477 in Brazil, 13 in Chile, five in Paraguay, and 10 in Uruguay. All study participants received a positive flu test, with one cohort receiving this years flu shot, and one cohort not receiving the flu shot.
Overall, the CDC learned that the VE for this years flu shot was at 34.5%, including 58.7% among patients with comorbidities, 39% among young children, and 31.2% among older adults.
The CDC explained that while this years VE is lower than it was in 2023, its still in historical range to effectively protect against influenza A; past data has shown that the flu shot typically has a VE between 34-53% for influenza A.
The study found that vaccination likely prevented around 37% of flu-related hospitalizations across South America this year.
These interim VE estimates suggest that although the proportion of hospitalized patients who were vaccinated was modest, vaccination with the Southern Hemisphere influenza vaccine significantly lowered the risk for hospitalization, the CDC explained. Northern Hemisphere countries should, therefore, anticipate the need for robust influenza vaccination campaigns and early antiviral treatment to achieve optimal protection against influenza-associated complications.
Vaccination rates are down
Another key finding from this study pointed to the overall lower vaccination rates happening around the world since the COVID-19 pandemic.
The CDC found that just one in five patients had received a 2024 flu vaccine, which is lower than what these figures were before the pandemic. The agency lists vaccine misinformation, hesitancy, and disruptions in routine immunization services as the primary reasons for lower vaccination rates since the COVID-19 pandemic.
However, with that in mind, they explained that the flu shot remains one of the most effective ways to prevent severe complications, hospitalizations, and death related to the flu.
Photo Credit: Consumer Affairs News Department Images
Posted: 2024-10-07 11:55:23
