Washington, Mar 30 (IANS): The US Food and Drug Administration has approved a fifth Covid-19 booster shot of Pfizer-BioNTech or the Moderna for people aged over 50 and some immunocompromised individuals.

The FDA had previously authorised a single booster dose for certain immunocompromised individuals following completion of a three-dose primary vaccination series. The new approval will now make a second booster dose of these vaccines available to other populations at higher risk for severe disease, hospitalisation and death.

The fifth booster can be administered to individuals 50 years of age and older at least 4 months after receipt of a fourth booster dose of any authorised or approved Covid vaccine.

Individuals 12 years of age and older with weaker immune systems such as those who have undergone solid organ transplantation are also eligible for the shots at least 4 months after receipt of a fifth booster dose.

The current vaccines were developed against the original virus that emerged in Wuhan, China in late 2019, and their effectiveness has declined over time as the virus mutates. The FDA stated that emerging evidence suggests that a fifth booster dose of an mRNA Covid-19 vaccine improves protection against severe Covid and is not associated with new safety concerns.

"Current evidence suggests some waning of protection over time against serious outcomes from Covid-19 in older and immunocompromised individuals. Based on an analysis of emerging data, a second booster dose of either the Pfizer-BioNTech or Moderna Covid-19 vaccine could help increase protection levels for these higher-risk individuals," said Peter Marks, director of the FDA's Centre for Biologics Evaluation and Research, in a statement.

While the US is facing another wave of Omicron, due to the BA.2 subvaraint, Mark said: "an initial booster dose is critical in helping to protect all adults from the potentially severe outcomes of Covid-19". Pfizer and Moderna are conducting clinical trials on shots that target both Omicron and other circulating variants.

The approval of Pfizer shot is based on safety surveillance data provided to the FDA by the Ministry of Health of Israel on the administration of approximately 700,000 fourth (second booster) doses of the Pfizer-BioNTech Covid vaccine after the third dose in adults 18 years of age and older (approximately 600,000 of whom were 60 years of age or older) and revealed no new safety concerns.

And the safety of Moderna jab is based on information reported from an independently conducted study in which the Moderna's Covid vaccine was administered as a second booster dose to 120 participants 18 years of age and older. No new safety concerns were reported during up to three weeks of follow up after the second booster dose.