Quantifying the waning of humoral immunity.

Immunological memory is a defining feature of immunity, yet surprisingly there is no consensus on how to quantitatively describe how antibody titers wane over time. A major problem is that the slow waning of antibody titers requires the collection of data for decades post-infection or vaccination. Our analysis of the largest existing dataset shows that a power-law model describes antibody waning better than other frequently used models. Our analysis suggests: (i) Protective levels of antibodies to many vaccine/virus antigens may be maintained for longer than previously estimated. (ii) The rate of waning of antibodies to protein toxoid vaccines such as tetanus may be similar to those elicited by live virus infections. (iii) The long-term waning of antibodies can be estimated from data for a much shorter time-frame of about 1-3 years following immunization, suggesting that using a power-law analysis could allow rapid estimation for the waning of immunity to new vaccines.