Field effectiveness of highly pathogenic avian influenza H5N1 vaccination in commercial layers in Indonesia

Abstract

Although vaccination of poultry for control of highly pathogenic avian influenza virus (HPAIV) H5N1 has been practiced during the last decade in several countries, its effectiveness under field conditions remains largely unquantified. Effective HPAI vaccination is however essential in preventing incursions, silent infections and generation of new H5N1 antigenic variants. The objective of this study was to asses the level and duration of vaccine induced immunity in commercial layers in Indonesia. Titres of H5N1 haemagglutination inhibition (HI) antibodies were followed in individual birds from sixteen flocks, age 18–68 week old (wo). The study revealed that H5N1 vaccination had highly variable outcome, including vaccination failures, and was largely ineffective in providing long lasting protective immunity. Flocks were vaccinated with seven different vaccines, administer at various times that could be grouped into three regimes: In regime A, flocks (n = 8) were vaccinated two or three times before 19 wo; in regime B (n = 2), two times before and once after 19 wo; and in regime C (n = 6) three to four times before and two to three times after 19 wo. HI titres in regime C birds were significantly higher during the entire observation period in comparison to titres of regime A or B birds, which also differed significantly from each other. The HI titres of individual birds in each flock differed significantly from birds in other flocks, indicating that the effectiveness of field vaccination was highly variable and farm related. Protective HI titres of >4log2, were present in the majority of flocks at 18 wo, declined thereafter at variable rate and only two regime C flocks had protective HI titres at 68 wo. Laboratory challenge with HPAIV H5N1 of birds from regime A and C flocks confirmed that protective immunity differed significantly between flocks vaccinated by these two regimes. The study revealed that effectiveness of the currently applied H5N1 vaccination could be improved and measures to achieve this are discussed.

Zoonotic Potential of Influenza A Viruses: A Comprehensive Overview

“…This is making it hard to select of a representative and genetically stable prepandemic candidate vaccine strain. Additionally, effective vaccination of animals against IAV can be influenced by several factors including, but not limited to, on-farm biosecurity measures [ 271 , 272 ], immune response of different bird species [ 272 ], immunosuppression, uncontrolled distribution and storage of the vaccines, and interference of maternal immunity with early vaccination of the offspring [ 273 ]. Rearing habits can also complicate the situation.…”

The Pandemic Threat of Emerging H5 and H7 Avian Influenza Viruses

“…Despite this campaign, outbreaks of HPAI H7N9 in poultry are ongoing [ 155 ], and the potential for future outbreaks and zoonotic infections remains. Importantly, vaccination of poultry does not typically confer sterilizing immunity, and most avian influenza vaccines reduced clinical illness and spread but do not block infection or viral replication in birds [ 156 , 157 ]. As a result, vaccination may drive antigenic drift of the virus as observed Marek’s disease [ 158 ], and this may result in the reemergence of the H7N9 viruses.…”

Peer Review #1 of "Individual and flock immunity responses of naïve ducks on smallholder farms after vaccination with H5N1 Avian Influenza vaccine: a study in a province of the Mekong Delta, Vietnam (v0.1)"

“…These results are consistent with findings of Tarigan et al who reported that outcomes of field H5N1 vaccination were highly variable and farm-related. Specifically, HI titers of individual birds in each flock differed from those of birds in other flocks [30]. Second, GMTs varied on the farm level (Fig.…”