Moderna Vaccine's Side Effects

choi

(1)
(a) Except the typical sore arm after the first dose on Feb 17, 2021, I had no other side effects.
(b) On Mar 27 following, I received the booster (or second dose) -- both doses came from Moderna (based in Cambridge, Mass). That afternoon I did not feel well. That evening Boston temperature fell to ~30 degrees (which was typical) but I sensed cold and malaise. Returning to the shelter, I went to bed, but quivered on bed with a blanket on top of me.  I was better the following morning.
(2) On Saturday (Mar 20), an acquaintance -- a female bar tender who works and lives in New Hampshire, who came to Boston occasionally to meet with her boyfriend (both are about 60s), once I told her that I received the second dose of the vaccine, specifically asked me about reaction following the second dose. It seemed to that she knew something. I mentioned (1) to her, and asked her why she inquired about the second dose in particular. She said many people reported the same after the second dose, and let on that she would not take vaccination as a result. That evening, I recalled news paper accounts that COVID-19 patients felt malaise, bone-chilling and shaken (all described to be worst in their lives), and wondered whether the side effects comes from host's immune reaction rather than induced by the virus itself (because in all COVID-19 vaccines, S protein (S for surface) alone will be produced in the host (be the vaccine mRNA or delivered via adenovirus).
(3) This morning (Mar 22) I could not find a single research report on the cause of vaccines' side effects.
(4) However, when I re-read
Fact Sheet for Healthcare Providers Administering Vaccine (Vaccination Providers). FDA, December 2020, at page 10
https://www.fda.gov/media/144637/download
("OVERALL SAFETY SUMMARY * * * In clinical studies, the adverse reactions in participants 18 years of age and older were pain at the injection site (92.0%), fatigue (70.0%), headache (64.7%), myalgia (61.5%), arthralgia (46.4%), chills (45.4%), nausea/vomiting (23.0%), axillary swelling/tenderness (19.8%), fever (15.5%), swelling at the injection site (14.7%), and erythema at the injection site (10.0%)" )