Who was the most at risk during Spanish flu and why?

The Spanish flu was in 1918 and 1919. There was no vaccine or antibiotics during this time and infants and children were at risk the most. Childrens health was not like adults health but still improving. Plus as a parent back then, if you had 12 children, you would be considered lucky if half of them survived. The Spanish flu made it worse. People over 65 were also at risk.