First Covid-19 shot

Yeah, this Wuhan virus affects different people in different ways. My 62 year old sister-in-law is a RN. She was masked and working in a cubicle at the hospital when she became infected. It took her a month to get over the major symptoms but it took her 5 months to get over the fatigue.
I recently met and talked with a guy who got his first shot because he is 52 with asthma. He has had a non-stop headache since the shot. He doesn’t know if he should take the second. The doctor has no advice on whether the second shot will clear his headache, make it worse, or have no affect. He is struggling with the decision.
I have three friends (65 years old) who have taken the shots and have had no adverse reaction or side affects.