London, Aug 2 (Prensa Latina) Tamiflu antibiotic prescribed for severe viral infections, including swine flu, may cause secondary effects in children, a study has said.

Researchers of the British Agency of Protection observed reactions to the medicine, such as headaches, stomach pains, nausea and nightmares in children between the ages of 11 and 12 who received preventive treatment for the disease.

Of the total 248 children who took part in the study, 51 percent reported adverse effects.

Although experts consider these symptoms were mild in nature, they point out that the antibiotic should be administered only when there are symptoms of A(H1N1) viral flu infection, the study published in the latest issue of the Eurosurveillance journal, said.

However, the head physician of the British government, Liam Donaldson, said Saturday: 'All medicines have secondary effects. It is a question of evaluating the benefits for a patient regardless of unwanted reactions.'