hope your Tigger gets well soon. it is awful when a friend is ill.
i lost my last one to FIV. my Demelza has had every jab the vets supply and i take her back for boosters every year, pricy but worth it. cats are very sensitive to emotion and will usually try to comfort anyone they consider family.
my thoughts are with you and Tigger.
(Demelza sends her love to Tigger)