The England players have all taken anti-malaria tablets ahead of their World Cup opener against Italy in Manaus on Saturday.
The 23-man party took the Malarone tablets, which can cause side-effects including stomach cramps, dizziness and sickness, during their breakfast on Tuesday morning.
While manager Roy Hodgson is concerned about his players getting struck with illness, the 66-year-old has insisted that the tablets are worth it to prevent his stars contracting the disease.
"As far as I'm concerned, I've got to go with medical opinion and if the doctors are telling me that when we go to Manaus the players must take malaria tablets, whether it has side-effects or not, what do I do?" PA quotes Hodgson as saying
"I can't turn around and say 'we will not take malaria tablets' because the bottom line is better stomach cramps or whatever it is for one player in 10 than have someone contract malaria because that would be unthinkable."
After England play Italy, they will face Uruguay and Costa Rica in Group D.
