But their study assumes day of birth vaccination increases immunity later compared to delayed start. It does not.
by James Lyons-Weiler, PhD, Popular Rationalism, ©2026
(Oct. 24, 2026) — An 83 percent projected increase in chronic infections combines delayed vaccination with a large assumed effect of decline in vaccine completion – an assumption is not backed by data.
Parents deciding when their newborn should receive a hepatitis B vaccine deserve an answer to a specific question: what additional protection does vaccination at birth provide compared with beginning later and completing the series? A new simulation study in Annals of Internal Medicine estimates a whopping 83% increase in chronic infections under a shared decision-making strategy and recommends restoring universal birth-dose vaccination. Yet its headline comparison changes both the timing of vaccination and the proportion of children who complete it. That makes the result a conditional forecast of a policy package, with an unresolved question about how much of the projected benefit belongs to the birth dose itself.
Amir Mohareb and colleagues modeled 3.6 million U.S.-born infants over their first 20 years. They assumed vaccine completion rates of 91.1% to universal birth-dose vaccination, 87.1% to vaccination beginning at two months, and 50.0% to shared decision-making. The resulting counts of chronic HBV infections are 255, 303, and 467. These are outputs from a Markov model, which moves a simulated population through health states using specified probabilities. The 2026 birth cohort has not been followed for 20 years.
The arithmetic deserves to be visible beside the relative percentages. All three strategies apply to the same population and horizon, so their projected risks can be compared directly.
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