In an air-handling system that provides cooled air to occupants of a building, most of the air is returned from the space back to the air handler to be reused. This is called â¦ Return Air, or RA. However, some fresh air (called Outside Air, or OA) must be mixed in.
Polio is a viral infection that can cause permanent paralysis. The inactivated poliovirus vaccine (IPV) is usually given at ages 2 months, 4 months, 6â18 months, and 4â6 years. Though the oral poliovirus vaccine (OPV) is still used in many parts of the world, it has not been used in the United States since 2000.
A Look at Each Vaccine: Polio Vaccine. The inactivated polio vaccine (or IPV) is now the only vaccine given in the United States to prevent polio. IPV is given as a series of four shots at 2 months, 4 months, 6 to 18 months, and again at 4 to 6 years of age.aralysis caused by polio occurs when the virus replicates in and attacks the nervous system. Two polio vaccines have been available since 1955. The inactivated polio vaccine (IPV) was available first, given as a shot in 1955. A more convenient form, given as liquid drops via the mouth, was developed in 1961.