The CDC has announced that the booster shot you get for the COVID-19 vaccine does not have to match the original vaccine you got. Meaning, you can get the Moderna booster shot even if you got the Pfizer vaccine the first time. Booster shots are available for people 65 years and older, for people that are between the ages of 18-64 with underlying health conditions, and people that work in high risk environments. Another stipulation is that you can only get the booster shot if you have gotten one of the mRNA vaccines and it must be at least six months since your last dose of the vaccine.
It may seem odd that you can suddenly mix and match boosters with vaccines, but research actually shows that mixing them can create a stronger antibody response. Research also shows that none of the booster shots is better than the others, but research does show a benefit to getting a booster shot.
It remains unclear when booster shots will become available for everyone.