Influence of Population Demography and Immunization History on the Impact of an Antenatal Pertussis Program

Abstract

Background. Antenatal pertussis vaccination is being considered as a means to reduce the burden of infant pertussis in low- and middle-income countries (LMICs), but its likely impact in such settings is yet to be quantified.Methods. An individual-based model was used to simulate the demographic structure and dynamics of a population with characteristics similar to those of LMICs. Transmission of pertussis within this population was simulated to capture the incidence of infection in (1) the absence of vaccination; (2) with a primary course only (three doses of diphtheria, tetanus, and pertussis vaccines [DTP3] commencing in 1985, 1995, or 2005 at 20%, 50%, or 80% coverage); and (3) with the addition of an antenatal pertussis program.Results. Modeled annual incidence averaged over the period 2015–2024 reduced with increasing DTP3 coverage, regardless of the year childhood vaccination commenced. Over the same period, the proportion of infants born with passive protection did not change substantially compared with the prevaccination situation, regardless of DTP3 coverage and start year. We found minimal impact of antenatal vaccination on infection in all infants when mothers were eligible for a single antenatal dose. When mothers were eligible for multiple antenatal doses, incidence in infants aged 0–2 months was reduced by around 30%. This result did not hold for the full 0- to 1-year age group, for whom antenatal vaccination did not reduce infection levels.Conclusions. While antenatal vaccination could potentially reduce infant mortality in LMICs, broader gains at the population level are likely to be achieved by focusing efforts on increasing DTP3 coverage.

Potential Impact of Changes in the Schedule for Primary Diphtheria-Tetanus Toxoids-Pertussis Immunization as Control Strategy for Pertussis

“…effective vaccine dose and thus enter 1 AI P class (P AI : partial acquired immunity). The assumption that upon infection susceptible individuals enter the full symptomatic stage is often used in the modeling of pertussis (9,(22)(23)(24), although other approaches have been used too. ( 25 P boost their immunity when they get in contact with infected individuals, entering the immune class R. As the infection fades out at a constant rate, individuals in I 1 , I 2 and I 3 are transferred to R. Individuals who acquired maternal antibodies when born are assigned to the X 0 class, which has the same degree of immunity as 1 AI P .…”

Model-based estimation of the impact on rotavirus disease of RV3-BB vaccine administered in a neonatal or infant schedule

“…Models that include demographic dynamics also offer the ability to explore long-term trends in immunity and demographic change. 35 In particular, such models could be used to assess potential impacts of immunization programs on rotavirus strain replacement, with implications for ongoing vaccine effectiveness. 36 …”

Infection-acquired versus vaccine-acquired immunity in an SIRWS model

“…Our finding that decreased primary infection may not have a substantial impact on the overall infection prevalence due to secondary infections is consistent with that of Águas et al (2006). Others ( Águas et al, 2006;Campbell et al, 2016) have included immune boosting into their transmission models. However, different from Águas et al (2006) who modelled the boosting of immunity as an infectious process, our interpretation of boosting as a non-infectious process allows immune boosting to be more easily triggered than a transmissible infection (ν > 1).…”

“…Where immunity is temporary, it wanes over time but may be subsequently boosted upon asymptomatic reexposure, as observed for measles (Whittle et al, 1999) and pertussis (Cattaneo et al, 1996). Mathematical models of vaccine-preventable infectious diseases (Glass and Grenfell, 2003;Águas et al, 2006;Wearing and Rohani, 2009;Lavine et al, 2011;Campbell et al, 2016) are based on the susceptibleinfectious-recovered-susceptible (SIRS) framework (Keeling and Rohani, 2008), where every individual in a population is categorised by one of three states based on his or her immune status: susceptible (S) to infection, infected and infectious (I) if they can transmit the infection, and recovered (R) from infection and immune. As immunity wanes, recovered individuals become susceptible to infection again.…”