The World Health Organization (WHO) on Monday recommended that immunocompromised people be given an additional dose of the Covid-19 vaccine, due to their higher risk of breakthrough infections after standard immunisation.

The Strategic Advisory Group of Experts on immunisation said the additional dose should be offered "as part of an extended primary series since these individuals are less likely to respond adequately to vaccination following a standard primary vaccine series and are at high risk of severe Covid-19 disease".

WHO vaccine director Kate O'Brien, referring to...