Why would the cdc recommend certain groups of people

Explanation:

Flu shots are usually recommended to people with delicate health. Influenza usually hits children that are usually 12 moths old or younger, older people, aged 65 and older. It hits people who are under constant stress due to work or personal life. Also, ones who suffered from any serious disease which weakened their immune system. It hits pregnant women, obese people, people who take too much medicament, and ones suffering from chronic diseases.