Why Some Vaccines Require More Than One Dose

Despite being declared beaten in 2000, measles is back, due largely to declining vaccination rates in parts of the United States. "We should not be in this boat," Dr. Pritish Tosh, an infectious diseases physician and researcher at the Mayo Clinic, told The Huffington Post. "This is a completely preventable disease." That's because of the measles, mumps and rubella vaccine, which Tosh called "phenomenal" in its ability to protect large percentages of the general population. The vaccine is one of several different vaccines, however, that are given in multiple doses. Children receive the first dose of the MMR vaccine between 12 and 15 months and the second before they go to school, around age 4 to 6. Every vaccine ever created has to take many variables into consideration, he explained, including the individual pathogen or bug; how our immune systems respond to it; what parts of the bug can be used to generate an immune response that is protective in nature; and also how long that response will last. Because that equation is notably complex, sometimes a second (or third) dose is a good idea. "Sometimes, if you take a large group of people with one vaccination you might expect 90 percent [to be protected]," he said. "But if you give a second dose, you may get up to 98 percent." Rather than testing the population to find the 10 percent not protected by the first dose, "what is probably a more straightforward strategy is just giving two doses to insure you have that high leve...
Source: Science - The Huffington Post - Category: Science Source Type: news