Denis Marke, manager of the Expanded Programme on Immunization, revealed the figure at the start of a week-long immunization campaign that is to vaccinate about 1.3 million children nationwide.
Ninety-two percent of the suspected cases were children under five, he said, while infants accounted for 29 percent and children aged one to four took up another 64 percent.
He attributed the large number of suspected cases identified during the assessment period to the fact that children were not immunized in the second half of 2014 because of the Ebola outbreak.
Most of the children under one year old are likely to have missed one or more vaccine doses, he said, adding they should be vaccinated this time.
The ministry of health, the United Nations children's fund, UNICEF and the World Health Organization will use the vaccination campaign to provide essential health services to the public, the official said.
Their objective, he said, is to achieve a 95 percent coverage of life-saving interventions for women and children, especially kids aged 59 months and below, to reduce the mortality and morbidity rates in Sierra Leone.