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The safety and effectiveness of vaccines are under constant study. Because vaccines are designed to be given routinely during well-child care visits, they must be extraordinarily safe. Safety testing begins as soon as a new vaccine is contemplated, continues until it is licensed, and is monitored indefinitely after licensure.
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Answer:the decline of lichens is an important indicator of an imbalance in the ecosystem. this research can help system ecologists predict how pollution will affect the entire ecosystem
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