Here is the current Mayo guidance on vaccine boosters: "Are COVID-19 vaccine boosters recommended?
Currently, the CDC and the FDA state that people in the U.S. who have been fully vaccinated don’t need a vaccine booster. This is because fully vaccinated people are protected from severe disease and death with the COVID-19 virus, including from COVID-19 variants. Most COVID-19 hospitalizations and deaths are among people who are unvaccinated.

However, COVID-19 vaccine manufacturers continue to research and test booster doses."

As the Delta variant spreads, and CDC, FDA & the vaccine manufacturers begin to learn more, it is quite likely a booster will be recommended, at least for the most vulnerable people.

As for an anti-body test, there are a couple tests being used very selectively on people on immunosuppressant drugs, such as transplant patients. The rest of us are being asked to wait for further guidance.
Sue