"Booster Shot Effectiveness Preventing Severe Cases and Hospitalization Drops from 87% to 31% After 5 Months"

A citizen is receiving a COVID-19 vaccine at the COVID-19 vaccination center set up at Sadang Sports Complex in Dongjak-gu, Seoul.
[Image source=Yonhap News]

[Asia Economy Reporter Hwang Sumi] A study has found that the effectiveness of COVID-19 vaccine booster shots in preventing severe illness and hospitalization significantly decreases after five months.

According to a report by The New York Times (NYT) on the 11th (local time), the U.S. Centers for Disease Control and Prevention (CDC) released these findings through the "Morbidity and Mortality Weekly Report (MMWR)."

The research team funded by the CDC analyzed data from over 241,200 adults aged 18 and older who were infected with COVID-19 and visited emergency rooms or urgent care clinics, and over 93,400 who were hospitalized, across 10 U.S. states from August 26 last year to January 22 this year.

This period included the time when the Delta and Omicron variants each accounted for more than 50% of new cases, becoming the dominant strains.

The analysis showed that within two months after the second vaccine dose, the effectiveness in preventing visits to emergency rooms or urgent care facilities was 69%, but this dropped to 37% after five months.

Receiving a booster shot restored this rate to 87%, but it also weakened over time. The effectiveness in preventing visits to emergency rooms or urgent care clinics within 4 to 5 months was 66%, which fell to 31% after five months, the research team reported.

However, the researchers added that since only a small number of people had received a booster shot more than five months ago, estimates related to this period may not be reliable.

Additionally, because this study focused on people who showed symptoms and sought hospital care, if these individuals were biased toward older adults or those with compromised immune systems, the booster shot’s effectiveness might appear weaker than it actually is, NYT reported.

Other studies have shown that while the vaccine’s effectiveness in preventing severe illness and hospitalization may diminish somewhat in those aged 65 and older, it still provides strong protection in healthy young adults.

NYT also analyzed that these findings increase the possibility that a fourth dose may be necessary for high-risk groups who could develop complications or die.

Earlier, on the 9th, Dr. Anthony Fauci, director of the U.S. National Institute of Allergy and Infectious Diseases (NIAID), stated, "Another booster shot, that is, a fourth vaccine dose for those who have received messenger RNA (mRNA) vaccines, may be necessary," adding, "This may depend on age or underlying health conditions."

This content was produced with the assistance of AI translation services.