Modeling and predicting the long-term effects of various strategies and objectives of varicella-zoster vaccination campaigns

ABSTRACT

Background: Susceptible, exposed, infected, and recovered (SEIR) models are increasingly developed and used, but their simplicity contrasts with the wide variety of scenarios before launching vaccination campaigns.

Methods: We investigated the effects of some model-building choices (targets, pace, coverage rate) on the results of SEIR models in the case of vaccination against varicella and herpes zoster.

Results: The analysis demonstrated the need for a progressive unvaccinated to vaccinated transition and a dynamic system-equilibrium before vaccination onset. When several doses are considered, new compartments are needed to account for vaccination histories. For varicella, the delay to reach the expected coverage rate and the pace until reaching this rate have significant impacts, especially on the short-term incidence. The impact of vaccination through herd immunity should be systematically investigated.

Conclusions: Graphs help understanding the progress of instantaneous incidence; however, tables of cumulative average incidence over decades should be preferred because of higher stability.

KEYWORDS:

• SEIR models
• immunization strategy
• vaccination modeling
• varicella
• herpes zoster
• prediction

Acknowledgments

The authors thank François Simondon (Sanofi Pasteur MSD) for his contribution to several rounds of opinion exchange about the subject and the formulation of several model choices.

Declaration of interests

H Bricout and M-L Kürzinger are affiliated to Sanofi Pasteur MSD. The authors have no other relevant affiliations or financial involvement with any organization or entity with a financial interest in or financial conflict with the subject matter or materials discussed in the manuscript apart from those disclosed.

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