Ans. is 'a' i.e., 1, 3, 5 days ANTI-TYPHOID VACCINES The old parenteral killed whole-cell vaccine was effective but produced strong side-effects. So, they are not used now. Two safe and effective vaccines are now licensed and available : - 1.The Vi polysachharide vaccine It is composed of purified Vi capsular polysaccharide from the Ty2 strain of S.Typhi. It is administered subcutaneously or intramuscularly. Only one dose is required. The vaccine confers protection 7 days after injection. To maintain protection, re-vaccination is recommended every 3 years. The vaccine is licensed for individuals aged 2 years. - It does not elicit immune response in children < 2 years. The vaccine is stable for 6 months at 37deg C and for 2 years at 20degC. The recommended storage temprature is 2-8degC. The Vi polysaccharide vaccine can be co-administered with other vaccines relevant for international travellers-such as yellow fever and hepatitis A Acyclovir is given to prevent the development of systemic disease in varicella infected immunosuppresed patients & can halt the progression of zoster in adults. Varicella zoster immunoglobulin given within 72 hrs of exposure can prevent chicken pox and is recommended in exposed immunocompromised persons. A live attenuated varicella vaccine is recommended for children between 12-18 months. It is effective even if given within 3-5 days after exposure. 2.The Ty 21a oral vaccine It is an orally administered, live attenuated Ty2 strain of S.Typhi in which multiple genes (including for Vi Capsular polysaccharide) have been mutated chemically. This lyophilized vaccine is available in 2 preparations : ? 1. Enteric coated capsules - Used for travellers to developing countries. It is used in individuals 5 years of age. 2.Liquid suspension - Used by public health programmes for young children in developing countries. It can be administered from the age of 2 years. Vaccine is administered on 1, 3 and 5the day, i.e., a 3-dose regimen is recommended. Vaccine confers protection 7 days after the last dose. The recommendation is to repeat this series (3 doses) every 3 years for people living in endemic areas, and every year for individuals travelling from non-endemic to endemic countries. Ty 21 a requires storage at 2-8degC, it retains potency for approximately 14 days at 25degC. Proguanil and antibacterial drugs should be stopped from 3 days before until 3 days after giving Ty 21 a, as these drugs may harm live bacteria. The vaccine is not efficacious if administered at the time of ongoing diarrhea. Avoided during diarrhoea as efficacy will reduce. Can be given to HIV +ve, asymptomatic persons with CD4 cell count of > 200/mm3 Well tolerated and has low rates of adverse events. Not recommended in congenital or acquired immunodeficiency, acute febrile illness, acute intestinal infection and in patients on antimitotic drugs May be given simultaneously with live vaccines of polio, cholera, yellow fever and MMR.