Pertussis vaccine greatly reduced the incidence of adverse effects compared to the earlier "whole-cell" pertussis vaccine, however immunity wanes faster after the acellular vaccine than the whole-cell vaccine. Between 10% and 50% of people given the whole-cell vaccines develop redness, swelling, soreness or tenderness at the injection site and/or fever, less than 1% experience febrile seizures or long periods of crying, and less than 1 out of every 1,000 to 2,000 people vaccinated have a hypotonic-hyporesponsive episode. The same reactions may occur after acellular vaccines, but are less common. Side effects with both types of vaccines, but especially the whole-cell vaccine, are
Tay–Sachs disease Researchers are looking at gene therapy or enzyme replacement therapy as possible treatments. Tay–Sachs disease is typically first noticed in infants around 6 months old displaying an abnormally strong response to sudden noises or other stimuli, known as the "startle response". There may also be listlessness or muscle stiffness (hypertonia). The disease is classified into several forms, which are differentiated based on the onset age of neurological symptoms. Until the 1970s and 1980s, when the disease's molecular genetics became known, the juvenile and adult forms of the disease were not always recognized as variants of Tay–Sachs disease. Post-infantile Tay–Sachs was