A nurse is teaching a client about the purpose of checking vaccine titers. Which client statement indicates an understanding of the teaching?

A. A titer measures the presence of antibodies in the blood, indicating immunity to a disease, not current infection or contagiousness. Testing for active infection requires other laboratory tests, such as PCR or culture, not a titer. B. Titers measure immunity status but do not dictate the precise dosage of a vaccine. Vaccine doses are standardized, and titers are used to decide whether a booster is necessary, not the exact amount to administer. C. Titers are used to assess immunity, particularly for individuals with uncertain vaccination history or those at risk of inadequate immune response. Allergic reactions are unrelated to whether a titer is needed. D. Vaccine titers are laboratory tests that measure the presence and level of specific antibodies in the blood. If the titer shows insufficient antibodies, it indicates that the individual did not mount an adequate immune response, and a repeat vaccination or booster may be required. This statement demonstrates accurate understanding of the purpose of titers.