Antibody Titer Kinetics: Primary vs Booster Response

Vaccination Events

Antigen dose strength 1.0×

Simulation speed 4 days/s

Immune State

Below protective threshold

Antibody titer0.0 AU/mL

Days since last dose—

Memory B-cell pool0.0 U

How it works

Each dose triggers plasma cells to secrete antibody, and a fraction of the responding B cells differentiate into long-lived memory B cells. Three coupled quantities are integrated every frame:

dP/dt = −P/τP              (plasma-cell secretion activity decays)
dA/dt =  P − A/τA          (titer A rises with secretion, decays with serum half-life)
dM/dt = −M/τM               (memory pool decays very slowly)

On a dose of strength s at memory level M:
  boost = 1 + k·M           (anamnestic amplification)
  P += s · boost
  M += g · s / (1 + M/Mmax)  (diminishing-returns recruitment)

Primary dose — first exposure. No memory pool yet, so boost ≈ 1: a slow, modest rise (~7–14 simulated days to peak) that decays back down over weeks.
Booster dose — because memory B cells persist from the primary dose, the anamnestic (secondary) response fires with boost > 1: production starts higher and the titer overshoots the primary peak while rising faster.
Antibody titer — visualised as the swarm of small particles orbiting the germinal centre; particle count and glow track A(t) in real time.
Memory B-cell pool — the ring of gold nodes around the germinal centre; it barely decays between doses, which is exactly why a booster produces a faster, larger response than the original dose.
The dashed line on the scrolling titer graph marks the protective threshold used for the status readout above.

This is a simplified two-compartment pharmacokinetic model of humoral immunity — the same qualitative shape (slow primary rise, fast high secondary rise) is what real serology studies measure after prime-boost vaccination schedules (e.g. two-dose mRNA or hepatitis B series).

Antibody titer Memory B cells Protective threshold

⚠ Couldn't load the 3D engineThree.js failed to load from the CDN. Check your connection and reload.