Describe what a vaccine is made of and how it prevent infection.

Viruses use the host's machinery to make copies of themselves. however, some human viruses require a type of replication that humans do not normally have. for example, humans normally do not have the ability to convert rna into dna. how can these types of viruses infect humans, when human cells cannot perform a particular role that the virus requires? a) the virus causes mutations in the human cells, resulting in the formation of new enzymes that are capable of performing these roles.b) the viral genome codes for specialized enzymes not in the host.c) the virus infects only those cells and species that can perform all the replication roles necessary.d) viruses can stay in a quiescent state until the host cell evolves this ability.

A5-year-old boy suddenly begins coughing while eating peanuts. he is choking and gagging. when he is brought to the ed, but he is awake and is able to give his name. on physical examination, his vital signs are stable. on examination of the chest, inspiratory stridor and intercostal and suprasternal retractions are apparent. which of the following is the most appropriate initial step in management? - allow patient to clear foreign object by spontaneous coughing- clear oropharynx with multiple blind sweeps with finger- position patient and perform back blows- stand behind patient and perform abdominal thrusts- perform emergency tracheostomy and take to surgery

How does emergency conception reduce the risk of pregnancy