The introduction of the conjugated typhoid vaccine in India (Peda TyphTM), and for the first time in the world, has come as one of the vaccines on the wish list of pediatricians living in the South of Globe. This novel vaccine has been found to be safe and effective in inducing very high levels of immune response (>90%) in infants, young children and adults. Since this vaccine induces ‘T’ cell dependent response, it would get boosted by field exposure and is expected to confer long lasting immunity. This new vaccine can be used to vaccinate and protect patients after clinical recovery and thus prevent disease carriers and relapses. We wish to offer our views on the previous correspondence on this issue(1,2).

Serologic correlates of typhoid immunity induced by Vi antigen was first reported by Felix and Pitt in 1935(3). Over the years the protective immunity conferred by Vi antigen has been well established and adopted by the WHO(4). The commonly known antigens of S. typhi viz ‘O’ & ‘H’ antigens induce serological response which are not protective in nature.

The valuable suggestion for bridging studies can only be taken up when an equivalent vaccine becomes available(1). Clinical trials are suggested involving more volunteers of all age groups over longer periods to establish that results of Peda TyphTM vaccine shall be similar to the Vi-rEPA vaccine in the Vietnam trials. Bio-Med (P) Ltd shall support any such initiative to bring more scientific information. Already more than 30000 doses of Peda TyphTM have been used over past 6-7 months all over India in all age groups. If doctors cooperate by providing serum samples for analysis, huge database can be created.

Reservations have been expressed on the relevance of vaccination for control of typhoid in India(2). Typhoid is very prevalent in whole of India. Everyone knows about typhoid as a common disease which has affected atleast one family member over 20 years time. The disease is in the memory of everyone due to its characteristic fever lasting for over 3 weeks, damaging consequences and high cost of treatment.

Typhoid vaccine was withdrawn from the UIP of Government of India in 1985 since the whole cell typhoid vaccine available at that time was highly reactogenic and provided very low protective value. The withdrawl of typhoid did not signal the significance of typhoid in India. Epidemiologists in affected countries would like to see control of typhoid by vaccination of over 60-70% population from the current levels of 4-5% only. Vaccination is at least 10 times cheaper and will save innumerable man days lost, doctor’s time, and hospital space, and the pain and suffering etc.

The launch of Vi conjugated typhoid vaccine (Peda TyphTM) is expected to bring an end of age old disease of man, since Salmonella typhi has no other host except man as was the case with smallpox virus.

Competing interests: Author is an employee of Bio-Med(P) Ltd, which manufactures Peda Typh.TM