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COVID Booster Efficacy Weakens After 4th Month - CDC

Medically reviewed by Via Roderos, MD, MBA · Internal or General Medicine

Written by Jason Inocencio · Updated Apr 04, 2022

    COVID Booster Efficacy Weakens After 4th Month - CDC

    People who have received their COVID-19 boosters might have a reason to worry. The US Centers for Disease Control and Prevention (CDC) reported that the booster doses of the Pfizer and Moderna mRNA vaccines weaken substantially. The waning COVID booster efficacy happens four months after the booster has been administered. 

    CDC methods for their study

    The new CDC study covers adults during the period of August 26, 2021 to January 22, 2022. More than 241,204 visits to the emergency department or urgent care clinics were recorded. More serious 93,408 hospitalizations were also studied.

    Vaccine efficacy was estimated by comparing the odds of a positive COVID-19 test between vaccinated and unvaccinated patients. They used statistical methods to control for calendar week and geographic area while adjusting for age. The level of local transmission and patient characteristics like comorbidities were factors.

    COVID booster efficacy falters

    Vaccine efficacy against COVID-associated emergency department or urgent care visits was 87% two months after the booster. It fell to 66% by the fourth month. Vaccine efficacy against hospitalization was 91% in the first two months. It fell to 78% after the booster by the fourth month.

    “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.

    Chief Medical Adviser to the President of the United States Anthony Fauci spoke during a recent COVID briefing. Fauci said that a fourth dose might be needed for subsets of people who had weaker immune responses. These include the elderly and the immunocompromised.

    Vaccination saves lives

    The World Health Organization (WHO) said in July 2021 that vaccines offer strong protection but protection takes time to build. People must take all required doses of a vaccine to build full immunity. Vaccines can take 2-3 weeks from the final vaccination to be fully effective. The WHO noted that it is important to continue all precautions during this period to protect yourself and others.

    Vaccines do not provide full 100% protection, thus breakthrough infections can happen. If vaccinated people do get sick, they are likely to have milder symptoms. Vaccinated individuals rarely experience severe illness or die from COVID.

    The WHO still stresses how important it is to be vaccinated as soon as possible. More vaccinations mean build building immunity in communities faster. That will then lead to a return to pre-pandemic normalcy. COVID booster efficacy may falter but that does not mean vaccination should not be a priority.

    New anti-COVID antibody authorized

    The US Food and Drug Administration (FDA) also recently issued emergency use authorization for an antibody to battle the Omicron variant. The monoclonal antibody Bebtelovimab will be used for the treatment of mild to moderate COVID-19.

    Bebtelovimab is meant for use by adults and pediatric patients aged 12 and older who test positive for COVID-19. This can be administered if they are at high risk for progression to severe COVID including hospitalization and death.

    Pharmaceutical company Lilly developed this antibody. A clinical trial showed that bebtelovimab has strong promise against the now-dominant Omicron variant.

    Key takeaways

    The Centers for Disease Control and Prevention revealed in a study that COVID booster efficacy may grow weaker four months after it is administered. The data covers the Pfizer and Moderna mRNA vaccines so far and it should be noted that the observations were done on a limited number of cases with confirmed Omicron variant. Nevertheless, this kind of drop-off in efficacy may lead to further boosters. The WHO remains consistent in its stand that vaccination is necessary to battle the coronavirus. Pharmaceutical company Lilly developed an antibody called bebtelovimab that has shown promise against Omicron.

    For more on coronavirus, click here.


    Hello Health Group does not provide medical advice, diagnosis or treatment.

    Medically reviewed by

    Via Roderos, MD, MBA

    Internal or General Medicine

    Written by Jason Inocencio · Updated Apr 04, 2022

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