Create a measles post-exposure prophylaxis (PEP) intervention

Usage

InterventionMeaslesPEP(
  name,
  mmr_efficacy,
  ig_efficacy,
  ig_half_life_mean,
  ig_half_life_sd,
  mmr_willingness,
  ig_willingness,
  mmr_window,
  ig_window,
  target_states,
  states_if_pep_effective,
  states_if_pep_ineffective,
  agent_groups = integer(0)
)

Arguments

name: Name of the intervention.
mmr_efficacy: Probability of MMR vaccine efficacy.
ig_efficacy: Probability of immunoglobulin (IG) efficacy.
ig_half_life_mean: Mean of the half-life of immunoglobulin (IG) in days.
ig_half_life_sd: Standard deviation of the half-life of immunoglobulin (IG) in days.
mmr_willingness: Probability that an individual will accept MMR vaccine.
ig_willingness: Probability that an individual will accept immunoglobulin (IG).
mmr_window: Time window for MMR vaccine administration.
ig_window: Time window for immunoglobulin (IG) administration.
target_states, states_if_pep_effective, states_if_pep_ineffective: Integer vectors of target and destination states (see details).
agent_groups: Optional integer vector of group (e.g. classroom) membership, with one entry per agent, in agent order. When supplied, PEP is offered only within the group(s) of the identified case(s). Defaults to integer(0), meaning the whole population is treated as a single exposed group (see details).

Value

An object of class epiworld_globalevent representing the measles PEP intervention.

Details

This functions creates a global event that represents a post-exposure prophylaxis (PEP) intervention for measles. The intervention includes the administration of MMR vaccine and immunoglobulin (IG) to individuals after exposure to the virus, with the goal of reducing the probability of infection and preventing the spread of the disease.

The process involves both PEP Measles-Mumps-Rubella (MMR) vaccine and immunoglobulin (IG). The system decides which agent gets MMR or IG based on the time since exposure and the willingness to accept PEP. The flow is the following:

Agents in target_states are eligible for PEP if they are willing to accept it (based on pep_willingness).
If the agent is already infected (for example, in a latent state) for at most mmr_window days, they are offered MMR vaccine. Otherwise, they are offered IG.
Susceptible agents are offered the MMR vaccine, and if they accept, they are automatically moved out of the quarantine process.
Agents who were already infected and got either MMR or IG may move out of the quarantine process if the PEP is effective (based on mmr_efficacy or ig_efficacy). The destination state depends on whether the PEP was effective or not, and is determined by states_if_pep_effective and states_if_pep_ineffective, respectively.

Since IG winds down over time, the IG "tool" may be removed from the agent as a function of the half-life of IG (based on ig_half_life_mean and ig_half_life_sd). Particularly, after applied, the IG "tool" will have a random duration based on a normal distribution with mean ig_half_life_mean and standard deviation ig_half_life_sd. Once the duration is over, the IG "tool" is removed from the agent, and they are again eligible for PEP if they are exposed again.

Who is offered PEP

Public health rarely has time to trace individual contacts. When a case is identified, the exposed group is treated as exposed as a whole, and the only question is how long ago that exposure started. By default that group is the entire population, which is appropriate for a single classroom but misleading when the population is really a set of separate communities.

agent_groups circumscribes the response. Supply one group label per agent, in agent order, and PEP is offered only to agents sharing the label of an identified case. Labels are arbitrary integers: agents with the same label are in the same group. For example, with 60 agents in three classrooms, agent_groups = rep(1:3, each = 20). A vector whose length is neither zero nor the number of agents is an error, since it is matched to agents by position.

Each group is also timed from its own exposure, so a case identified in one classroom does not shorten (or extend) the window available to another.