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Covid booster efficacy wanes substantially by fourth month - Study

  • 12-02-2022 11:40am
    Registered Users Posts: 8,913 ✭✭✭ Danno

    The efficacy of third doses of the Pfizer and Moderna mRNA vaccines wanes substantially by the fourth month after administration, a new study by the US Centers of Disease Control and Prevention has said.

    Though it is now well documented that vaccine efficacy goes down after two doses, relatively little has been published on the duration of protection after a booster.

    The new study was based on more than 241,204 visits to an emergency care clinic and 93,408 hospitalisations among adults with Covid-19-like illness between 26 August, 2021 and 22 January, 2022.

    Vaccine efficacy was estimated by comparing the odds of a positive Covid test between vaccinated and unvaccinated patients and using statistical methods to control for calendar week and geographic area,

    The study also adjusted for age, the level of local transmission, and patient characteristics like co-morbidities.

    During the Omicron-predominant period, vaccine efficacy against Covid-associated emergency department or urgent care visits was 87% during the two months after a third dose, but fell to 66% by the fourth month.

    Vaccine efficacy against hospitalisation was 91% in the first two months, but fell to 78% by the fourth month after a third dose.

    "The finding that protection conferred by mRNA vaccines waned in the months after receipt of a third vaccine dose reinforces the importance of further consideration of additional doses to sustain or improve protection," the authors concluded.

    From: Covid booster 'wanes substantially' by fourth month (

    Wonder will Philip "snake oil" Nolan be on the airwaves to give us his opinion on this?

    It begs the question - will fourth, fifth, sixth and so forth boosters be required going forward?