Answer:
Positive feedback is used to build more contractions.
Explanation:
Positive feedback mechanism in humans is also observed during childbirth which is induced by the pressing of the ovarian wall by the baby.
The pressing sensation is passed to the brain via different nerves, and in response, the brain stimulates the pituitary to produce oxytocin.
Oxytocin is responsible for the contractions of the uterine muscles which cause the movement of the fetus towards the cervix, further increasing the stimulus.  
The positive feedback loop continues until the baby is born.
 
        
                    
             
        
        
        
Answer:
Please mark me brainliest
Explanation:
Many of these diseases can be prevented by the use of viral vaccines, which stimulate protective immunity against the virus without causing major disease. Viral vaccines may also be used in active viral infections, boosting the ability of the immune system to control or destroy the virus.