Except in so far as in any particular case any privilege or immunity is waived by the Organisation, all officials of the Organisation (other than those referred to in Article 4 above) shall enjoy—
(a) immunity from suit and legal process in respect of words spoken or written and all acts done by them in the course of the performance of their official duties;
(b) exemption from income tax in respect of emoluments received by them as officers or servants of the Organisation.