The United States Food and Drug Administration (USFDA) authorized both the Pfizer-BioNTech and Moderna's Covid -19 vaccine to administer an additional dose in people with weaker immune systems, which includes organ transplant recipients. The rollout of booster dose is based on FDA's evaluation, according to which the administration of third vaccine doses may increase protection in this population.

The third dose will accordingly be administered at least 28 days following the two-dose regimen of the same vaccine to individuals 18 years of age or older (ages 12 or older for Pfizer-BioNTech) who have undergone solid organ transplantation, or who are diagnosed with conditions that are considered to have an equivalent level of immune-compromised, the Food and Drug Administration said in a statement on Thursday.

People with organ transplantation and those immune-compromised in a similar manner have a reduced ability to fight infections and other diseases, and they are especially vulnerable to infections, including Covid-19.

Mr. Janet Woodcock, Acting FDA Commissioner said: "The country has entered yet another wave of the Covid-19 pandemic, and the FDA is especially cognizant that immune-compromised people are particularly at risk for severe disease. After a thorough review of the available data, the FDA determined that this small, vulnerable group may benefit from a third dose of the Pfizer-BioNTech or Moderna Vaccines."

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