You have heard wrong, after the first injection of an antigen the body starts production of antibodies (or B-cells) this progresses over time. When the second injection (commonly called a ‘booster’) is given then the body reacts to produce greater numbers of antibodies, or ‘boosts’ the number of B-cells. The older you are the higher the likelihood of systemic and local reaction.
Antibodies do not attack antibodies.
Adverse reactions to covid vaccines are generally mild and transient, even if you are unlucky enough to get a systemic reaction it is better than getting the disease, everyone should get their shots.
If anyone has concerns, look at the science yourself, don’t just read the headlines.
As an example, scroll to the final paragraph of this.....
https://www.cdc.gov/vaccines/covid-19/info-by-product/pfizer/reactogenicity.htmlClick to expand...