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12077 & OHM - vo 6.1 Introd SCI-201 -P 6.3 Respire Scl201. X @& Newtab | Chat Thread + 0 Cc 23 webtexts.com/courses/85310/traditional_book/chi 4% & (@) : Mf contents OURLIVING WORLD The effectiveness of a vaccine depends on the individual and on the pathogen being vaccinated against. For a vaccine to be effective, it has to stimulate the adaptive immune system. Sometimes an individual's immune system does not respond. This can happen due to complications from diabetes, age, or HIV infection. Some people have \"unlucky\" genetics: Their body does not have a B cell that responds to the particular component used for vaccination. Alternatively, the individual may not mount a sufficient response to the vaccine, or may do so too slowly. The flu and similar pathogens present different challenges. These viruses mutate quickly, appearing in different forms from year to year. In addition, multiple variations can appear at the same time. To develop the correct vaccine, scientists must predict which strains are most likely to spread throughout the population. Sometimes their prediction is incorrect and the vaccine they develop is ineffective. For this reason, the flu shot is effective 67% of the time on average. MULTIPLE-CHOICE QUESTION Which statement suggests the measles vaccines are effective? O There were 750,000 cases of measles resulting in over 500 deaths in 1958. () The number of measles cases fell dramatically after vaccines became available. () There are less than 150 measles cases every year. Vaccines are most effective against a particular pathogen when a majority of a population chooses to get that vaccine. When enough people get the same vaccine, the entire population can experience herd immunity. Sometimes, high rates of vaccination can eradicate a disease entirely. You'll learn more about this phenomenon on the next page. ad \">