Encouraged, they introduced the DTPvaccine, which protects children from diphtheria, tetanus and pertussis (still a top seller), followed by an anti-snake-venom serum for snakebites.
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But selling only in India and mainly to the government wasn't a very profitable business. (A DTPvaccine might sell for three cents a dose in India, as mandated by the government, but triple the price in the export market.) So Poonawalla shifted course.