Washington, Oct 21 : The US Food and Drug Administration (FDA) has authorised Covid-19 booster doses of Moderna and Johnson & Johnson, and approved "mix and match" booster dose for currently available approved Covid-19 vaccines. The agency on Wednesday authorised the use of a single booster dose of the Moderna Covid-19 vaccine at least 6 months after completion of the primary shots to people 65 years of age and older, 18 through 64 years of age at high risk of severe Covid-19, and 18 through 64 years of age with frequent institutional or occupational exposure to SARS-CoV-2, Xinhua news agency reported. As for the Johnson & Johnson booster dose, the FDA authorised the use of a single booster dose at least 2 months after completion of the single-dose primary regimen to individuals 18 years of age and older. A single booster dose of any of the available Covid-19 vaccines may be administered as a "mix and match" booster dose following completion of primary vaccination with a different available Covid-19 vaccine, according to the FDA. For instance, a person who got a Johnson & Johnson vaccine could receive one from Moderna or Pfizer-BioNTech as a booster. "The available data suggest waning immunity in some populations who are fully vaccinated," said Acting FDA Commissioner Janet Woodcock in a statement. "The availability of these authorized boosters is important for continued protection against Covid-19 disease." The decision came after an FDA advisory committee voted last week to recommend authorizing Moderna and Johnson & Johnson's Covid-19 booster doses. In September, the FDA authorized the first booster shots for the Pfizer-BioNTech Covid-19 vaccine, allowing a single booster dose of the Pfizer-BioNTech vaccine be administered at least 6 months after completion of the primary series to individuals 65 years of age and older, and 18 through 64 years of age with frequent institutional or occupational exposure to SARS-CoV-2. A recent study of the "mix and match" approach funded by the US National Institutes of Health found no safety concerns using different vaccines as a booster. The study found that people who received the Johnson & Johnson vaccine produced stronger antibody levels after they got booster shots made by Moderna or Pfizer-BioNTech, compared to boosters from Johnson & Johnson. /IANS