Regarding polio which of the following statement is TRUE?

95% of patients with polio infections are asymptomatic. Patients who become ill develop manifestations such as aboive poliomyelitis, nonparalytic poliomyelitis and paralytic poliomyelitis. In patients with spinal poliomyelitis, flaccid paralysis occur over 2-3 days in an asymmetric distribution and affects the proximal muscles of the lower extremities more frequently. Paralysis of the shoulder girdle often precedes intercostal and diaphragmatic paralysis, which leads to diminish chest expansion and decreased vital capacity. The 4 doses of oral polio vaccine and inactivated parenteral vaccine are given at age 2, 4, 6-18 and at 4-6 years. Ref: CURRENT Medical Diagnosis & Treatment 2014 chapter 32.