Serology-Anchored Comparison of Self-Reported Vaccination: Reported Hepatitis B Series Completion Exceeds Vaccine-Consistent Immunity in the Same Participants

A large secondary literature draws adult vaccination status from the National Health and Nutrition Examination Survey (NHANES), whose accuracy is rarely quantified alongside it. The objective of this article is to quantify that accuracy in the same participants, because its size and direction decide whether these items can support a coverage claim. The methods we used pooled ten NHANES cycles (1999–2018, adults ≥ 20 years; analytic n 13,992–48,959 by vaccine) and compared self-reported, completed-series uptake with a within-person biological reference. That reference exists for hepatitis B in 2015–2016 only and does not validate the hepatitis A or human papillomavirus (HPV) estimates. Our results are that among the 4473 respondents with both measures, self-reported vaccination rates (33.5%, 95% CI: 30.5–36.5%) stood 10.9 percentage points (7.5–14.3) above vaccine-consistent serology (22.6%, 19.9–25.2%), a ratio of 1.48 (1.30–1.67). They disagreed in both directions, 845 reporting the series without the serologic profile and 294 carrying the profile without reporting it, so the difference is not a measure of over-reporting. Tested directly, it was a near-constant multiple across sex, age, and race. Published National Health Interview Survey coverage, matched on dose definition, population, and year, gave ratios up to 3.00. Four adjusted estimators placed the effect of a usual source of care at 5.7–6.5 percentage points for hepatitis B and 2.5–3.2 for HPV, three excluding zero and the causal forest’s wider interval covering it. The conclusions drawn are that the two measures are not interchangeable and that NHANES figures should be read as reported uptake, not coverage surveillance.