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In the face of soaring numbers of infection rates caused by the highly contagious delta variant of SARS-CoV-2, and the debate that immunity triggered by COVID-19 vaccines could fade over time, some countries are considering whether to administer further doses to those who have been fully vaccinated.

It may seem like only yesterday that people were looking at the date they could get fully protected by being vaccinated, now there’s talk that our safety may require another shot in the arm.

Only last week, the Food and Drug Administration (FDA) amended the emergency use authorizations (EUA) given to Pfizer-BioNTech and Moderna to allow additional dose of their COVID-19 vaccines for certain immuno-compromised people.


It’s common for protection from vaccines to decrease over time. 

Concerns over waning immunity and COVID-19 variants have convinced some countries to deploy extra vaccine doses — but it’s not clear to scientists whether most people need them.

The delta variant now accounts for near 100 percent of new Covid-19 cases in the U.S., according to the CDC.

What is the rationale behind the need for COVID-19 vaccine booster doses?

COVID-19 booster vaccines are not a new idea. Right from when the vaccines were first introduced last year, scientists have acknowledged that boosters may someday be needed. This would mean a third shot of vaccine from Pfizer-BioNTech or Moderna, or a second dose of Johnson & Johnson, which are the three approved vaccines in the U.S.

Some of the reasons why COVID-19 vaccine booster doses may be needed include;

  • Waning immunity against infection or disease, in particular severe disease, over time 
  • Reduced protection against variants of concern

After how long will you need a COVID-19 booster?

According to a plan announced last week in a Press Briefing by White House COVID-19 Response Team and Public Health Officials, all adults who received a two-dose vaccine would be eligible for the third jab of the Pfizer or Moderna vaccine eight months from when they got their second one.

The timing of the announcement comes as something of a surprise. It was just a few days earlier that the FDA and CDC recommended a third shot of the Pfizer or Moderna vaccine for a more limited population — people who are moderate to severely immunocompromised.

The new plan has been endorsed by both the Food and Drug Administration and a Centers for Disease Control and Prevention advisory committee.

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Jennifer Billings is the Medical Editor at Medicwell. She is an Integrated medical doctor who has been published on Medicwell Blog, and is a regular contributor at MedCity News, Physician Family, and Psychology Today.