Sweden’s Health Agency recommended on Monday that people aged 80 or above should receive a second booster shot of COVID-19 vaccine, the fourth jab in total, to ward off waning immunity amid the rampant spread of the Omicron variant.

The recommendation also covered all people living in nursing homes or who receive assisted living services at home. The second booster shot should be administered at least four months after the first booster jab, the agency said in a statement.