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Volume 19, Number 8—August 2013

Research

Duration of Immunity to Norovirus Gastroenteritis

Kirsten Simmons, Manoj Gambhir, Juan Leon, and Ben LopmanComments to Author 
Author affiliations: Rollins School of Public Health, Emory University, Atlanta, Georgia, USA (K. Simmons, J. Leon, B. Lopman); Centers for Disease Control and Prevention, Atlanta (K. Simmons, B. Lopman); Imperial College London, London, UK (M. Gambhir)

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Table 3

Duration of immunity, fitted parameter estimates, and log-likelihood and basic reproductive number for models of duration of immunity to norovirus gastroenteritis

Parameter Symbol Model A Model B Model C Model D Model E Model F
Duration of immunity, y θ 5.1 (3.9–6.5) 5.1 (4.0– 6.7) 8.7 (6.8–11.3) 4.1 (3.2–5.1) 7.6 (5.6–8.0) 5.1 (3.9–6.6)
Probability of transmission per infected contact, 0–4 y q1 0.25 (0.21–0.31) 0.18 (0.15–0.21) 0.37 (0.14–0.91) 0.35 (0.27–0.44) 0.23 (0.19–0.25) 0.25 (0.21–0.31)
Probability of transmission per infected contact, >5 y
q2
0.050 (0.042–0.055)
0.036 (0.032–0.039)
0.094 (0.078–0.114))
0.062 (0.057–0.066)
0.051 (0.47–0.056)
0.050 (0.046–0.054)
Negative log likelihood 615.497 613.905 663.052 616.597 611.509 615.375
Annual incidence, %† 5.2 5.3 5.5 5.1 3.8 5.2
Basic reproductive number (all ages) R0 1.79 1.64 3.34 1.88 1.73 1.79
Basic reproductive number (0–4 y) R0 4.33 3.98 6.41 4.84 3.98 4.33

*Model A, only symptomatic infectiousness; model B, presyymptomatic and postsymptomatic infectiousness (low); model C, presymptomatic and postsymptomatic infectiousness (high); model D, innate genetic resistance; model E, genogroup 2 type 4 (GII.4); model F, no immune boosting by asymptomatic infection.
†Compared with an observed annual incidence 4.5% from Phillips et al. (5), except for model E, which should be compared with norovirus GII.4-specific incidence of 3.2%.

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