Inducing Herd Immunity against Seasonal Influenza in Long-Term Care Facilities through Employee Vaccination Coverage: A Transmission Dynamics Model

Table 1

The parameter values for each variable in the SEIR compartmental model. Surveillance data refers to values obtained from conducting surveillance among each of the long-term care facilities in New Mexico during the 2006-2007 influenza season.

Parameter	Parameter value (range); Current study	Parameter value; van den Dool et al. [16] study
Number of residents	Surveillance data (5–345)	30
Number of HCWs	Surveillance data (12–207)	30
Vaccination coverage among residents	Surveillance data (0%–99%)	0.75
Vaccination coverage among HCWs	Surveillance data (0–100%)	0-1
Number of days	120 (surveillance period)	80
Number of facilities	63	1
Size of general population	1,937,916 [17]	100,000
Contact ()	46% (36%–48%)	Unknown
Average number of visitors	0.7 (0–2) per resident per day	0.7 (0.4–1) per resident per day
Time step	8 hours	8 hours
Discharge mortality rate	1/425 per day	1/425 per day
Infectious rate	1/1.4 per day	1/1.4 per day
Recovery rate	1/1.4 per day	1/1.4 per day
HCWs immune from cross protection	30%	30%
Probability of casual contact between patients	7%	7%
Probability of close contact between patients	6%	6%
Probability of casual contact between HCW and patient	52%	52%
Probability of close contact between HCW and patient	69%	69%
Probability of casual contact between HCWs	91%	91%
Probability of close contact between HCWs	32%	32%
Ratio of close to casual transmission probability	2	2
Vaccine efficacy among patients	25%	25%
Vaccine efficacy among HCWs	73%	73%

HCW: healthcare worker.