Table 4.

Model parameters.

Parameter description	Symbol	Parameter value or prior value	Reference	Note
Transmission dynamic models
Duration of infectiousness
First infection	$1/{\gamma }_1$	10 days	65–67
Second infection	$1/{\gamma }_2$	7 days
Subsequent infection	$1/{\gamma }_3$	5 days
Relative risk of infection following
First infection	${\sigma }_1$	0.76	58–61
Second infection	${\sigma }_2$	0.6
Subsequent infection	${\sigma }_3$	0.4
Relative infectiousness
Second infections	${\rho }_1$	0.75	58,59,68
Subsequent infections	${\rho }_2$	0.51
Proportion of RSV infections leading to hospitalization
First infection			68–74	The probability of hospitalization given infection was estimated as the product of the probability of hospitalization given lower respiratory tract infections, the probability of lower respiratory tract infections given symptomatic infection (IS), and the probability of symptoms given infection: $\mathrm{Pr}\left(hosp\mathrm{\mid }I\right)=\mathrm{Pr}\left(hosp\mathrm{\mid }LRI\right)\times \mathrm{Pr}\left(LRI\mathrm{\mid }{I}_s\right)\times \mathrm{Pr}\left(I_s\mathrm{\mid }I\right)$ We estimated the age-specific probability by fitting polynomial regressions to reported aggregate probabilities for 3-month or 6-month age groups
0–1 months old	$h_{p,0-1}$	0.082
2–3 months old	$h_{p,2-3}$	0.048
4–5 months old	$h_{p,4-5}$	0.027
6–7 months old	$h_{p,6-7}$	0.016
8–9 months old	$h_{p,8-9}$	0.012
10–11 months old	$h_{p,10-11}$	0.012
1 year old	$h_{p,1y}$	0.010
2–4 years old	$h_{p,2-4y}$	0.007
$\ge 5$ years old	$h_{p,5+y}$	0.001
Second infection	$h_{s,a}$	0.4*$h_{p,a}$	59
Third+ infection	$h_{t,a}$	$0$	75
Waning rate of maternal immunity and cocooning effects (1/months)	$\omega$	$logN\left(-1,0.6\right)$	46–49,76
Transmission parameter*	$q$	$N\left(3,1\right)$	39	Truncated at (1, 5)
Amplitude of seasonality	$\alpha$	$N\left(0.2,0.05\right)$	39
Timing of seasonality	$\varphi$	$N\left(3.4,1\right)$	39	Truncated at (0, 2$\pi$)
Reporting fraction	$\theta$	$beta\left(2,2\right)$	39
Vaccine efficacy parameters
Relative risk reduction in infants	${\sigma }_i$	84.7% (50.0%–97.6%)	5,12,45	Maternal immunization
Relative risk reduction in mothers	${\sigma }_m$	90.0% (80.0%–100.0%)	12,25,45	Maternal immunization
The duration of vaccine-induced protection	$1/{\omega }_v$	150 days	12,46–49	Maternal immunization
The duration of protection of extended half-life monoclonal antibodies	$1/{\omega }_{mAb}$	275 days (150 days – 400 days)	9,27,47	Extended half-life monoclonal antibodies
The probability of seroconversion	$\mathrm{\xi }$	90.0% (80.0%–100.0%)	39,50	Live-attenuated vaccines
Duration of shedding of vaccine virus	$1/{\gamma }_v$	5 days	39,50	Live-attenuated vaccines
Coverage parameters
Ideal coverage	${\mathrm{C}}_i$	85.0%–95.0%
Realistic coverage
Maternal immunization	${\mathrm{C}}_r^{Mat}$	53%–70%	50
Extended half-life monoclonal antibodies	${\mathrm{C}}_r^{mAb}$	70%–82%	52
Live-attenuated vaccines	${\mathrm{C}}_r^{Live}$	70%–86%	52

*The basic reproductive number (R₀) was estimated from $R_0=\frac{\det \left({\beta }_{a,k}\right)}{{\gamma }_1}=\frac{\det \left(q{C}_{a,k}\right)}{{\gamma }_1},$ using the next-generation matrix method; the transmission parameter q was fitted to the data, $C_{a,k}$ is the contact matrix scaled by the proportion of the population within each age class.