The health ministry in the Republic of Congo has successfully vaccinated 400,000 children under the age of five against polio, officials said.

The campaign, which was mainly carried out to prevent the spread of polio from neighbouring Democratic Republic of Congo (DRC), took place in the administrative departments of Brazzaville, Pool in the south, Plateaux and Cuvette in the central region and Likouala in the north.

Congo's director-general of health, Damase Bozongo, said the June vaccination campaign was prompted by reports of new cases of wild poliomyelitis (polio) in the DRC in 2006.

"The wild polio virus was noticed in the DRC and it could reach us through border areas. We organised the vaccination campaign to prevent importation," said Bozongo. The campaign was supported by the UN World Health Organization (WHO) and the UN Children’s Fund (UNICEF).

Before the sustained polio vaccination campaigns, the DRC had the highest number of polio cases globally. During the 1980s, about 8,000 Congolese children contracted the disease. New cases have been reported in the DRC and Angola in recent years, but no new cases of polio have been reported in the Republic of Congo since 2000.

Poliomyelitis is caused by the polio virus, which enters the body orally, infecting the intestinal lining. It may proceed to the blood stream and into the central nervous system, causing muscle weakness and often paralysis.

In areas with poor hygiene and sanitation, polio spreads through human contact, usually by faecally contaminated water or food, but the virus can also be spread through coughing and sneezing in crowded environments.

Symptoms include fatigue, sore throat, fever, vomiting, gastro-intestinal disturbances, headache and pain in the neck and extremities. Weakness of muscles often leads to permanent paralysis and deformity of the limbs.