PROTECTIVE EFFICACY OF ORAL WHOLE-CELL RECOMBINANT-B-SUBUNIT CHOLERA VACCINE IN PERUVIAN MILITARY RECRUITS

The cholera epidemic in South America has reinforced the need for safe and effective oral vaccines. In a randomised, double-blind, placebo-c ontrolled efficacy trial among 1563 Peruvian military recruits we have investigated the protective efficacy of an oral inactivated whole-cel l/recombinant-B-subunit (WC/rBS) cholera vaccine. Participants were gi ven two oral doses of cholera vaccine or Escherichia coli K12 placebo, with an interval of 7-14 days. 1426 (91%) subjects received the two p rescribed doses and were followed up for a mean of 18 weeks (median 21 weeks). After vaccination, Vibrio cholerae O1 El Tor Ogawa was isolat ed from 17 subjects with diarrhoea. 16 of the cholera cases occurred 2 weeks or longer after the second dose of vaccine (14 placebo recipien ts, 2 vaccinees). We also detected 14 symptomless infections (11 [7 pl acebo recipients, 4 vaccinees]) 2 weeks or longer after the second dos e. The vaccine had significant protective efficacy against cholera (86 % [95% Cl 37-97], p<0.01) but not against symptomless infection (42% [ -96 to 85]). All cholera cases were in people of blood group O, who ma de up 76% of the study population (p<0.01). Two doses of WC/rBS vaccin e, given 1 to 2 weeks apart, provide rapid, short-term protection agai nst symptomatic cholera in adult South Americans, who are predominantl y of blood group O. Long-term efficacy studies in Peruvian adults and children are under way.