THE CAPSULAR POLYSACCHARIDE TYPHOID VACCINE CONTAINS 25 MICROGRAMS OF THE VI POLYSACCHARIDE ANTIGEN PER DOSE. A SINGLE DOSE OF 0.5 ML IS GIVEN BY DEEP SUBCUTANEOUS OR INTRAMUSCULAR INJECTION. BOOSTER DOSES MAY BE GIVEN EVERY 3 YEARS TO THOSE WHO REMAIN AT RISK. THE RESPONSE IN CHILDREN UNDER 18 MONTHS OF AGE MAY BE SUBOPTIMAL, AND THE DECISION TO VACCINATE WILL BE GOVERNED BY THE RISK OF EXPOSURE TO INFECTION.
IN THE USA, THE VI CAPSULAR POLYSACCHARIDE VACCINE AND THE LIVE ORAL TY 21A VACCINE ARE AVAILABLE. THE CAPSULAR POLYSACCHARIDE VACCINE IS GIVEN INTRAMUSCULARLY SIMILARLY TO THAT IN THE UK, WITH A BOOSTER DOSE SUGGESTED EVERY 2 YEARS. FOR THE ORAL VACCINE, 4 DOSES ON ALTERNATE DAYS ARE RECOMMENDED FOR BOTH PRIMARY IMMUNISATION AND BOOSTERS, WHICH ARE GIVEN EVERY 5 YEARS IF EXPOSURE CONTINUES.
IN AREAS WHERE TYPHOID IS ENDEMIC WHO ADVISES THAT IMMUNISATION SHOULD BE CONSIDERED AS PART OF THE ROUTINE SCHEDULES; EITHER THE VI CAPSULAR POLYSACCHARIDE VACCINE OR THE TY 21A LIVE ORAL VACCINE SHOULD BE GIVEN TO SCHOOLCHILDREN OVER THE AGE OF 2 YEARS. IMMUNISATION OF THE WHOLE COMMUNITY SHOULD ALSO BE CONSIDERED DURING AN OUTBREAK OF TYPHOID; IF THIS IS NOT POSSIBLE, PERSONS AGED 2 TO 19 YEARS SHOULD BE THE TARGET GROUP.