The COVID-19 vaccine booster shot is effective against the coronavirus, but the effectiveness wanes after about four months, the Centers for Disease Control and Prevention said Friday.

The findings: The CDC said Friday that effectiveness against urgent care and hospitalizations from COVID-19 was higher after the third vaccine dose compared to the second.

  • During the omicron variant’s spread, the booster shot’s effectiveness against COVID-19 emergency room visits and hospitalizations were 87% and 91% during the two months after a third dose.
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Yes, but: Those effectiveness numbers dropped to 66% and 78% by the fourth month after a third dose, according to the CDC.

Why it matters: “All eligible persons should remain up to date with recommended COVID-19 vaccinations to best protect against COVID-19–associated hospitalizations” and emergency room visits, according to the CDC.

The bigger picture: Experts have been saying for a while that the COVID-19 booster shot can provide strong protection against the coronavirus, including the highly transmissible omicron variant.

  • In late January, a CDC study by health care systems in 10 states — which included Intermountain Healthcare in Utah — found that the COVID-19 booster shot doubled the protection from the contagious omicron variant.
  • “Overall, those who received a booster dose had the most protection against emergency room visits, urgent care clinic visits, and hospitalizations,” said Dr. Rochelle Walensky, director of the CDC.