When do two to four month old babies typically get sick?

Immunity. A baby is seldom ill in the first few months of life. Much of mother's immunity transfers to the baby providing temporary protection that begins to wear off by three months. At this point, we begin to see fever, congestion, or diarrhea as a sign of babies new susceptibility to viruses.
Sick in 2-4 months. Anytime at any age, sickness can occur. Just observe, head elevation if cough occurs,
tylenol every 4 hrs for pain, temp. If appears ill or in distress, a pediatrician should
check since they are smaller, younger and more vulnerable to getting ill.