Table VI.

Model Inputs for the Albania Outbreak Model

Model input (symbol)	Best estimate	Source	Notes
Number of subpopulations	1		Focus model only on undervaccinated communities
Relative population size compared to all of Albania	0.5
Number of age groups	9		0–2; 3–17; 18–23 months; 2–4; 5–9; 10–19; 20–29*; 30–49*; ≥ 50 years
Number of mixing age groups	6		0–4; 5–9; 10–19; 20–29; 30–49; ≥ 50 years
Year when model run-up starts	1930
Year when R0 seasonality starts	1940
Year when die-out first allowed	1960
Average basic reproductive number (PV1) (R0)			Fitted within range for middle tier (Table III); assume higher values during 1996 outbreak than endemic viruses
- During run-up	7
- During 1996 outbreak	8
Proportional change in R0 due to seasonality ($\alpha$)	0.4
Day of seasonal peak in R(pd)	200 (July 19)	13
Relative weight of other age groups to force-of-infection ($\kappa$)			Assume highly heterogeneous mixing to allow accumulation of fully susceptibility adults despite secondary OPV exposure
- 0–4 years	0.5
- 5–9 years	0.97
- 10–19 years	0.97
- 20–29 years	0.95
- 30–49 years	0.7
- ≥ 50 years	0.7
Proportion of transmissions via oropharyngeal route ($p^{oro}$)	0.8	19	Fitted within range of expert assessments(19) and using Netherlands value as upper bound (Table V)
Per-dose take rate (tr)(PV1)			IPV take rates loosely based on field efficacy of IPV against type 1 poliomyelitis in the USA in 1954;(55) mOPV take rates based on assumed cumulative take after 1 mOPV1 dose and one tOPV dose a year later of 80% and 90% for poor and better cold chain conditions before and after 1970, respectively; increasing tOPV take rate reflects improving cold chain conditions
- IPV (Salk)	0.50a
- mOPV1, 1960–1970	0.55b
- mOPV1, 19701–1977	0.68b
- tOPV, 1978–1991	0.30c
- tOPV, 1992–1996	0.45d
Assumptions about IPV use 1958–1959		57	Coverage and schedule represent assumptions in the absence of details about IPV usage in Albania
- Coverage with 3 doses by age 2 years	0.72
Coverage with 1 mOPV1 dose (1960–1977) or 3 tOPV doses (1978–1996) by age 1 year	Time series	57,76,82	See Appendix A4 for values used
Characterization of annual mOPV campaigns 1960–1977		57
- Date of round (day number)	120 (April 30)
- Duration (days)	30
- Ages targeted	0–18 months
Characterization of routine tOPV vaccination 1978–1996		57	Coverage correction factor accounts for likely overreporting of coverage calculated from doses distributed;(82) booster dose at 5–6 years of age added to routine schedule in 1982(57)
- Coverage correction factor	0.9
- Cumulative effect of 3 primary doses at ages (months)	3
- Booster doses at ages (years)	1.5, 5
- Relative coverage of booster dose	0.5
Characterization of 1983 tOPV campaign		57	Campaign targeted children born 1979–1981; assume NID dates as for mOPV campaigns
- Number of doses, 2–4 years	1
- Effective impact ($\zeta$)	0.5
Date of introduction for 1996 outbreak	February 19, 1996	13	Fitted within previously characterized range
Characterization of spring’96 tOPV campaign		13, 57	Assume coverage significantly lower than official report of 98% coverage; campaigns targeted children ≥ 2 months of age, which represents one-third of the first age group in our model, leading to a relative coverage of one-third for this age group
- Number of doses, 3 months–4 years	2
- First day of first round (1996)	105 (April 8)
- First day of second round (1996)	134 (May 13)
- Duration of both rounds (days)	7
- Effective per-round impact ($\zeta$)	0.6
- Relative coverage for children aged 0–2	1/3
Characterization of outbreak response campaign		13, 57
- Number of doses, 0–49 years	2
- First day of first round (1996)	281 (October 7)
- First day of second round (1996)	315 (November 11)
- Duration of both rounds (days)	7
- Effective per-round impact ($\zeta$) (round 1; round 2)	0.82; 0.88

Acronyms: IPV = inactivated poliovirus vaccine; mOPV(1) = monovalent oral poliovirus vaccine (type 1); NID = national immunization day; PV1 = poliovirus type 1; tOPV = trivalent oral poliovirus vaccine; USA = United States of America

^*Age groups marked with an asterisk indicate age groups that count towards determining the fraction of newborns that receive maternal antibodies, based on the immune fraction in those age groups (see Appendix A1).

^aFor runs to verify behavior of other serotypes, we use take rates for IPV (Salk) of 0.6 and 0.5 for type 2 and 3, respectively.

^bFor runs to verify behavior of other serotypes, we use the same take rates.

^cFor runs to verify behavior of other serotypes, we use take rates for tOPV 1978–1991 of 0.55 and 0.27 for type 2 and 3, respectively.

^dFor runs to verify behavior of other serotypes, we use take rates for tOPV 1992–1996 of 0.70 and 0.40 for type 2 and 3, respectively.