Amsterdam, Oct 5 (IANS): The Amsterdam-based European Medicines Agency (EMA) has approved booster doses of the Pfizer/BioNTech Covid-19 vaccine for all people aged 18 and over.

The EMA said in a statement on Monday that data for the vaccine had shown a rise in antibody levels when a booster shot is administered approximately six months after the second dose in people aged 18 to 55, reports Xinhua news agency.

It recommended that the booster doses "may be considered at least six months after the second dose for people aged 18 years and older".

Meanwhile, the EMA also recommended an extra dose of Pfizer/BioNTech and Moderna vaccines for those with severely weakened immune systems.

The EMA said that it had given the green light after studies showed that an extra dose of these vaccines increases the ability of organ transplant patients with severely weakened immune systems to produce antibodies against the virus that causes Covid-19.

The extra dose should be given to the severely immune-compromised at least 28 days after their second dose, the EMA said.

"Although there is no direct evidence that the ability to produce antibodies in these patients protected against Covid-19, it is expected that the extra dose would increase protection at least in some patients," it said, adding that it will continue monitoring any new data on its effectiveness.

The agency also added: "The risk of inflammatory heart conditions or other very rare side effects after a booster is not known and is being carefully monitored."

Member states will take decisions related to booster vaccines, according to the EMA.