Question

How did polio change over time

Answer 1

Answer:

Over millennia, polio survived quietly as an endemic pathogen until the 1900s when major epidemics began to occur in Europe. Soon after, widespread epidemics appeared in the United States. By 1910, frequent epidemics became regular events throughout the developed world primarily in cities during the summer months

Explanation:

hope it helps

Answer 2

Answer:

• Between 1961 and 1996, children in the United States received four doses of the oral vaccine. This changed beginning in 1997 and continued throughout 1999 when children typically received two doses of the shot followed by two doses of the oral vaccine. Since that time, infants have received four doses of the shot.

Explanation:

i hope it helps you ☺️ ✌️