It is generally or it was believed that quinine is prophylactic. But several papers have questionned this believe and a large scale clinical trial from India in 1918 demonstrated that it is not the case and that large quantities of quinine have been swallowed by a large number of people without providing protection against the infection nor significantly reducing transmission
G Waugh Scott. Quinine prophylaxis in malaria. Brit Med Journal, 1918, May 11th.