diff --git a/NAMESPACE b/NAMESPACE
index aebaadca..287e0ee7 100644
--- a/NAMESPACE
+++ b/NAMESPACE
@@ -120,6 +120,7 @@ S3method(compute_terms,cohort)
 S3method(compute_terms,human)
 S3method(compute_terms,na)
 S3method(compute_terms,xde)
+S3method(dEIPdt,static)
 S3method(dHdt,numeric)
 S3method(dHdt,static)
 S3method(dLdt,basic)
@@ -314,6 +315,7 @@ export(compute_kappa_ty)
 export(compute_local_frac)
 export(compute_terms)
 export(compute_terms_steady)
+export(dEIPdt)
 export(dHdt)
 export(dLdt)
 export(dMYZdt)
diff --git a/R/adult-GeRM.R b/R/adult-GeRM.R
index dd1839ff..0cac2fae 100644
--- a/R/adult-GeRM.R
+++ b/R/adult-GeRM.R
@@ -109,7 +109,7 @@ dMYZdt.GeRM_dde <- function(t, y, pars, Lambda, kappa) {
     dGdt <- f*(M - G) - nu*G - (Omega %*% G)
     dYdt <- f*q*kappa*(M - Y) - (Omega %*% Y)
     dZdt <- Upsilon %*% diag(f_eip*q_eip*kappa_eip, nPatches) %*% (M_eip - Y_eip) - (Omega %*% Z)
-    dUdt <- as.vector((Omega_eip - Omega) %*% Upsilon)
+    dUdt <- as.vector(((1-dEIPdt(t,pars))*Omega_eip - Omega) %*% Upsilon)
 
     return(c(dMdt, dGdt, dYdt, dZdt, dUdt, kappa, f, q, g, sigma))
   })
diff --git a/R/adult-RM.R b/R/adult-RM.R
index 20c6357e..bc927f2b 100644
--- a/R/adult-RM.R
+++ b/R/adult-RM.R
@@ -105,7 +105,7 @@ dMYZdt.RM_dde <- function(t, y, pars, Lambda, kappa) {
     dPdt <- f*(M - P) - (Omega %*% P)
     dYdt <- f*q*kappa*(M - Y) - (Omega %*% Y)
     dZdt <- Upsilon %*% (fqkappa_eip * (M_eip - Y_eip)) - (Omega %*% Z)
-    dUdt <- as.vector((Omega_eip - Omega) %*% Upsilon)
+    dUdt <- as.vector(((1-dEIPdt(t,pars))*Omega_eip - Omega) %*% Upsilon)
 
     return(c(dMdt, dPdt, dYdt, dZdt, dUdt, f*q*kappa, g, sigma))
   })
diff --git a/R/eip.R b/R/eip.R
index 98cbccb0..5c0f4b19 100644
--- a/R/eip.R
+++ b/R/eip.R
@@ -10,6 +10,16 @@ EIP <- function(t, pars) {
   UseMethod("EIP", pars$EIPmod)
 }
 
+#' @title Compute the derivative of the EIP as a function of time
+#' @description This method dispatches on the type of `pars$EIPmod`.
+#' @param t current simulation time
+#' @param pars a [list]
+#' @return [numeric]
+#' @export
+dEIPdt <- function(t, pars) {
+  UseMethod("dEIPdt", pars$EIPmod)
+}
+
 #' @title Modify parameters due to exogenous forcing by all kinds of control
 #' @description Implements [EIP] for the static model (the EIP is constant)
 #' @inheritParams EIP
@@ -17,6 +27,13 @@ EIP <- function(t, pars) {
 #' @export
 EIP.static <- function(t, pars) {pars}
 
+#' @title This function computes the negative derivative of the EIP as a function of time
+#' @description Implements [EIP] for the static model (the dEIPdt=0)
+#' @inheritParams EIP
+#' @return [numeric]
+#' @export
+dEIPdt.static <- function(t, pars){0}
+
 #' @title Set up the static model for control forcing (do nothing)
 #' @param pars a [list]
 #' @return [list]
diff --git a/R/utils.R b/R/utils.R
index 583700a1..20cbb0a6 100644
--- a/R/utils.R
+++ b/R/utils.R
@@ -73,18 +73,20 @@ get_inits <- function(pars){
 #' @export
 parse_deout <- function(deout, pars){
   varslist = list()
-  varslist$time = deout[,1]
   if ('Lpar' %in% names(pars)) {
     varslist$L = parse_deout_L(deout, pars)
+    varslist$L$time = deout[,1]
   }
   if ('MYZpar' %in% names(pars)) {
     varslist$MYZ = parse_deout_MYZ(deout, pars)
+    varslist$MYZ$time = deout[,1]
   }
   if ('Xpar' %in% names(pars)) {
     varslist$XH = parse_deout_X(deout, pars)
+    varslist$XH$time = deout[,1]
   }
   varslist$terms = compute_terms(varslist, deout, pars)
-  varslist$terms$time = varslist$time
+  varslist$terms$time = deout[,1]
   varslist$deout = deout
   return(varslist)
 }
diff --git a/_pkgdown.yml b/_pkgdown.yml
index cfcc5965..a346b457 100644
--- a/_pkgdown.yml
+++ b/_pkgdown.yml
@@ -93,6 +93,8 @@ reference:
   contents:
   - EIP
   - EIP.static
+  - dEIPdt
+  - dEIPdt.static
   - setup_eip_static
 - subtitle: Ztrace
   desc: |
diff --git a/man/dEIPdt.Rd b/man/dEIPdt.Rd
new file mode 100644
index 00000000..25de2557
--- /dev/null
+++ b/man/dEIPdt.Rd
@@ -0,0 +1,19 @@
+% Generated by roxygen2: do not edit by hand
+% Please edit documentation in R/eip.R
+\name{dEIPdt}
+\alias{dEIPdt}
+\title{Compute the derivative of the EIP as a function of time}
+\usage{
+dEIPdt(t, pars)
+}
+\arguments{
+\item{t}{current simulation time}
+
+\item{pars}{a \link{list}}
+}
+\value{
+\link{numeric}
+}
+\description{
+This method dispatches on the type of \code{pars$EIPmod}.
+}
diff --git a/man/dEIPdt.static.Rd b/man/dEIPdt.static.Rd
new file mode 100644
index 00000000..2d5114cc
--- /dev/null
+++ b/man/dEIPdt.static.Rd
@@ -0,0 +1,19 @@
+% Generated by roxygen2: do not edit by hand
+% Please edit documentation in R/eip.R
+\name{dEIPdt.static}
+\alias{dEIPdt.static}
+\title{This function computes the negative derivative of the EIP as a function of time}
+\usage{
+\method{dEIPdt}{static}(t, pars)
+}
+\arguments{
+\item{t}{current simulation time}
+
+\item{pars}{a \link{list}}
+}
+\value{
+\link{numeric}
+}
+\description{
+Implements \link{EIP} for the static model (the dEIPdt=0)
+}