Data released this week by the Centers for Disease Control and Prevention indicate COVID-19 booster shots provided some protection against recent subvariants.

According to an early CDC estimate, the booster shots prevented 52% of symptomatic infections in the BA.5 subvariant and 48% of symptomatic infections against the XBB.1.5 subvariant among those ages 18-49. The data look specifically at people who had gotten their shots two or three months earlier.

The CDC looked specifically at people who had gotten the new bivalent booster against those considered fully vaccinated but had not gotten the updated shots.

In the last week, the XBB 1.5 subvariant has comprised an estimated 49% of U.S. COVID-19 cases.

Although most of the U.S. population is fully vaccinated, just 15.3% of those eligible have gotten an updated booster shot, according to CDC data.