Actually, you have antibodies starting about two weeks after the
first dose. During the clinical trials, they were saying that the vaccines were 50% effective after the first dose and you would receive "peak protection" of 90% about two weeks after the second dose. But that wasn't to say that you had no protection or antibodies at all after the first dose.
As it were, additional studies conducted by the CDC, using real-world people who received the vaccine in the earliest rounds, have revealed that the Pfizer and Moderna vaccines were 80% effective after the first dose! 80%!! That means that the second dose only adds an additional 10% of protection.
See it here:
https://www.cnbc.com/2021/03/29/cdc-...effective.html
Also, an antibody test (from your blood donations) won't tell you if the COVID vaccine is working or not. Antibody tests are looking for a certain protein in people who have already had the actual COVID virus. If you have tested negative four times, congratulations! That means that you've never had COVID! Though, those tests don't mean that your body still hasn't produced antibodies from the vaccine. The antibody test you took, I presume, was looking for a different "piece" than the ones the vaccines makes. The Atlantic had an article that's a bit wordy, but it explains it well.
The Atlantic:
https://www.theatlantic.com/science/...-tests/617981/
Washington Post, easier read, but less informative:
https://www.washingtonpost.com/lifes...antibody-test/
Finally, the CDC says that fully vaccinated people are free to visit other fully vaccinated people indoors without masks. They can also visit with unvaccinated low-risk people from a single household indoors without masks. Of course, you and your parents are welcome to operate at your own comfort level; but, it is not necessary to fully stay inside and not visit anyone.
See the CDC guidelines here:
https://www.cdc.gov/coronavirus/2019...-guidance.html