Trivalent and quadrivalent influenza vaccination effectiveness in Australia and South Africa: results from a modelling study.

George J Milne,Ian G Barr,Joel K Kelso,Nilimesh Halder,Jocelyn Moyes,Rhian Twine,Cheryl Cohen,Kathleen Kahn

doi:10.1111/irv.12367

Abstract

BackgroundA modelling study was conducted to determine the effectiveness of trivalent (TIV) and quadrivalent (QIV) vaccination in South Africa and Australia.ObjectivesThis study aimed to determine the potential benefits of alternative vaccination strategies which may depend on community‐specific demographic and health characteristics.MethodsTwo influenza A and two influenza B strains were simulated using individual‐based simulation models representing specific communities in South Africa and Australia over 11 years. Scenarios using TIV or QIV, with alternative prioritisation strategies and vaccine coverage levels, were evaluated using a country‐specific health outcomes process.ResultsIn South Africa, approximately 18% fewer deaths and hospitalisations would be expected to result from the use of QIV compared to TIV over the 11 modelled years (P = 0·031). In Australia, only 2% (P = 0·30) fewer deaths and hospitalisations would result. Vaccinating 2%, 5%, 15% or 20% of the population with TIV using a strategy of prioritising vulnerable age groups, including HIV‐positive individuals, resulted in reductions in hospitalisations and mortality of at least 7%, 18%, 57% and 66%, respectively, in both communities.ConclusionsThe degree to which QIV can reduce health burden compared to TIV is strongly dependent on the number of years in which the influenza B lineage in the TIV matches the circulating B lineages. Assuming a moderate level of B cross‐strain protection, TIV may be as effective as QIV. The choice of vaccination prioritisation has a greater impact than the QIV/TIV choice, with strategies targeting those most responsible for transmission being most effective.

Highlights

Seasonal influenza is an infectious respiratory illness responsible for an estimated 250 000–500 000 deaths globally each year.[1]
The reason for this difference is that the B lineage component of the trivalent inactivated vaccine (TIV), which was the same in both communities and based on the WHO Southern Hemisphere recommendations,[8] was less well matched to the circulating South African B strains than the Australian strains for the 11 years of the study
We have shown that the benefit of QIV over TIV is strongly related to which B lineages circulate in a given year and the lineage contained in the TIV

Summary

Introduction

Seasonal influenza is an infectious respiratory illness responsible for an estimated 250 000–500 000 deaths globally each year.[1] Young children, the elderly and those with other underlying health conditions such as HIV have an increased risk of developing complications of influenza, such as pneumonia.[2,3,4]. Vaccination to mitigate seasonal influenza is widely used in some countries, with 20% or more of the population being vaccinated annually in Australia, the UK and the United States, for example.[5,6,7] The most common vaccine in use over the last 30 years has been a trivalent inactivated vaccine (TIV) containing three vaccine strains: two influenza A strains [e.g. A(H1N1) and A(H3N2)] and an influenza B strain. A modelling study was conducted to determine the effectiveness of trivalent (TIV) and quadrivalent (QIV) vaccination in South Africa and Australia

Objectives

Methods

Results

Discussion

Conclusion