The effectiveness of the booster dose of Pfizer and Modern vaccines decreases over time, but is high against hospitalization four months after the injection, according to a study released Friday by U.S. health officials. This effect is now well known after two dose injections, but has not been much studied after the third injection.
The study examined 93,000 hospitals and more than 240,000 Covid 19-related visits to emergency departments in 10 U.S. states. It was conducted between August 2021 and January 2022, covering two waves associated with the Delta and Omigron types. In both periods, efficacy measured after the third dose was always higher than after the second dose, according to the Centers for Disease Control and Prevention (CDC), which published the study.
A percentage that is “high”
When Omigran became the primary variant, the efficacy against hospitalization for those receiving the third dose within two months was 91%. Percentage “high” according to CDC. Furthermore, after the arrival of Omicron, the effectiveness of the booster dose against emergency department visits was 87% within two months, 66% after four months, and 31% after five months.
However, the CDC notes that this latest figure is “accurate” because a small number of people in the study received their third dose five months ago. Overall, these results reinforce the importance of additional considerations for additional doses to maintain or improve protection against Covit-19, CDC write. During a news conference Wednesday, White House Health Adviser Dr. Anthony Fassi estimated that a vulnerable group, such as the elderly or those with immunodeficiency, would need a fourth dose in the future.
(Essential / AFP)