Association of vaccine handling conditions with effectiveness of live attenuated influenza vaccine against H1N1pdm09 viruses in the United States.

PURPOSE: This analysis examined potential causes of the lack of vaccine effectiveness (VE) of live attenuated influenza vaccine (LAIV) against A/H1N1pdm09 viruses in the United States (US) during the 2013-2014 season. Laboratory studies have demonstrated reduced thermal stability of A/California/07/2009, the A/H1N1pdm09 strain utilized in LAIV from 2009 through 2013-2014. METHODS: Post hoc analyses of a 2013-2014 test-negative case-control (TNCC) effectiveness study investigated associations between vaccine shipping conditions and LAIV lot effectiveness. Investigational sites provided the LAIV lot numbers administered to each LAIV recipient enrolled in the study, and the vaccine distributor used by the site for commercially purchased vaccine. Additionally, a review was conducted of 2009-2014 pediatric observational TNCC effectiveness studies of LAIV, summarizing effectiveness by type/subtype, season, and geographic location. RESULTS: From the 2013 to 2014 TNCC study, the proportion of LAIV recipients who tested positive for H1N1pdm09 was significantly higher among children who received a lot released between August 1 and September 15, 2013, compared with a lot shipped either earlier or later (21% versus 4%; P<0.01). A linear relationship was observed between the proportion of subjects testing positive for H1N1pdm09 and outdoor temperatures during truck unloading at distributors' central locations. The review of LAIV VE studies showed that in the 2010-2011 and 2013-2014 influenza seasons, no significant effectiveness of LAIV against H1N1pdm09 was demonstrated for the trivalent or quadrivalent formulations of LAIV in the US, respectively, in contrast to significant effectiveness against A/H3N2 and B strains during 2010-2014. CONCLUSIONS: This study showed that the lack of VE observed with LAIV in the US against H1N1pdm09 viruses was associated with exposure of some LAIV lots to temperatures above recommended storage conditions during US distribution, and is likely explained by the increased susceptibility of the A/California/7/2009 (H1N1pdm09) LAIV strain to thermal degradation. CLINICAL TRIAL REGISTRY: NCT01997450.

Development of live attenuated influenza vaccines against pandemic influenza strains.

Avian and animal influenza viruses can sporadically transmit to humans, causing outbreaks of varying severity. In some cases, further human-to-human virus transmission does not occur, and the outbreak in humans is limited. In other cases, sustained human-to-human transmission occurs, resulting in worldwide influenza pandemics. Preparation for future pandemics is an important global public health goal. A key objective of preparedness is to gain an understanding of how to design, test, and manufacture effective vaccines that could be stockpiled for use in a pandemic. This review summarizes results of an ongoing collaboration to produce, characterize, and clinically test a library of live attenuated influenza vaccine strains (based on Ann Arbor attenuated Type A strain) containing protective antigens from influenza viruses considered to be of high pandemic potential.

Genetic stability of live, cold-adapted influenza virus components of the FluMist/CAIV-T vaccine throughout the manufacturing process.

FluMist is a live-attenuated, trivalent influenza vaccine (LAIV) recently approved for intranasal administration. To demonstrate genetic stability during manufacture of the vaccine viruses in LAIV and a similar vaccine in development (CAIV-T), full genome consensus sequences were determined at multiple manufacturing stages for four influenza type A and five type B strains. The critical cold-adapted (ca), temperature-sensitive (ts) and attenuated (att) mutations were preserved in the virus manufacturing intermediates. Moreover, sequence identity was observed for all vaccine intermediates of the same strain. Minor sequence differences were noted in the shared gene segments of the vaccine viruses and their common progenitor master donor virus (MDV) and several of the hemagglutinin (HA) and neuraminidase (NA) genes contained nucleotide differences when compared to the wild-type parent. Nonetheless, all vaccine viruses retained the ca, ts, and att phenotypes. Thus, genetic and phenotypic stability of the vaccine viruses is maintained during the manufacture of LAIV/CAIV-T vaccines.

Genetic and phenotypic stability of cold-adapted influenza viruses in a trivalent vaccine administered to children in a day care setting.

The genetic and phenotypic stability of viruses isolated from young children following intranasal administration of the trivalent live-attenuated influenza virus vaccine (LAIV, marketed in the United States as FluMist) was evaluated by determination of genomic sequence and assessment of the cold-adapted (ca), temperature-sensitive (ts) and attenuated (att) phenotypes. The complete genomic sequence was determined for 56 independent isolates obtained from children following vaccination (21 type A/H1N1, 12 A/H3N2, 1 A/H3N1 and 22 type B viruses), 20% of which had no nucleotide misincorporations compared with administered vaccine. The remaining isolates had from one to seven changes per genome. None of the observed misincorporations resulted in predicted amino acid codon substitutions at sites previously shown to contribute to the ca, ts or att phenotypes, and all vaccine-derived isolates retained ca and ts phenotypes consistent with the observation that none of the vaccine recipients displayed distinctive symptoms. The results indicate that LAIV strains undergo very limited genetic change following replication in vaccine recipients and that those changes did not affect vaccine attenuation.

A bovine parainfluenza virus type 3 vaccine is safe and immunogenic in early infancy.

BACKGROUND: A phase 2 trial was conducted to assess in young infants the safety, tolerability, infectivity, and immunogenicity of multiple doses of an intranasal vaccine using bovine parainfluenza virus type 3 (bPIV3). METHODS: One hundred ninety-two healthy 2-month-old infants were randomized 1 : 1 : 1 to receive 1x10(5) median tissue culture infective dose (TCID(50)) bPIV3 vaccine, 1x10(6) TCID(50) bPIV3 vaccine, or placebo at 2, 4, 6, and 12-15 months of age. Safety information was collected by use of diary sheets and telephone interviews. Nasal wash and serum specimens were collected for assessment of infectivity and immunogenicity. RESULTS: The safety profiles of both dosages of bPIV3 were similar to that of placebo, with the exception of fever with temperature of >/=38.1 degrees C after dose 2 only, occurring in 34% of the 1x10(5) TCID(50) group, 35% of the 1x10(6) TCID(50) group, and 12% of the placebo group (P<.01). No vaccine-related serious adverse events were reported. The cumulative vaccine infectivity (isolation of bPIV3 and/or bPIV3 seroconversion) after dose 3 was similar in the 2 vaccine groups (87% in the 1x10(5) TCID(50) group and 77% in the 1x10(6) TCID(50) group) (P=.46). Seroconversion rates after dose 3, assessed by means of hemagglutination inhibition assay, after adjustment for decrease in maternal antibody titers, were 67% in the 1x10(5) TCID(50) group, 57% in the 1x10(6) TCID(50) group, and 12% in the placebo group (P<.01). Isolation of bPIV3 was common after dose 1, dose 2, or dose 3, but only 1 of 51 participants in the vaccine groups had bPIV3 isolated after dose 4. CONCLUSIONS: Multiple doses of bPIV3 vaccine were well tolerated and immunogenic in young infants.

Evaluation of attenuation, immunogenicity and efficacy of a bovine parainfluenza virus type 3 (PIV-3) vaccine and a recombinant chimeric bovine/human PIV-3 vaccine vector in rhesus monkeys.

Restricted replication in the respiratory tract of rhesus monkeys is an intrinsic property of bovine parainfluenza virus type 3 (bPIV-3) strains. This host range phenotype of bPIV-3 has been utilized as a marker to evaluate the attenuation of bPIV-3 vaccines for human use. Two safety, immunogenicity and efficacy studies in primates evaluated and compared three human parainfluenza virus type 3 (hPIV-3) vaccine candidates: biologically derived bPIV-3, a plasmid-derived bPIV-3 (r-bPIV-3) and a chimeric bovine/human PIV-3 (b/hPIV-3). These studies also examined the feasibility of substituting Vero cells, cultured in the presence or absence of foetal bovine serum, for foetal rhesus lung-2 (FRhL-2) cells as the tissue culture substrate for the production of bPIV-3 vaccine. The results demonstrated that (i) Vero cell-produced bPIV-3 was as attenuated, immunogenic and efficacious as bPIV-3 vaccine grown in FRhL-2 cells, (ii) plasmid-derived bPIV-3 was as attenuated, immunogenic and efficacious as the biologically derived bPIV-3 and (iii) the b/hPIV-3 chimera displayed an intermediate attenuation phenotype and protected animals completely from hPIV-3 challenge. These results support the use of bPIV-3 vaccines propagated in Vero cells in human clinical trials and the use of b/hPIV-3 as a virus vaccine vector to express foreign viral antigens.

Safety and immunogenicity of a live-attenuated influenza vaccine blended and filled at two manufacturing facilities.

This study was designed to compare the safety and immunogenicity of a trivalent live-attenuated, cold-adapted influenza vaccine (CAIV-T) blended and filled at two different manufacturing facilities (Medeva and Aviron-PA). The vaccines contained approximately 10(7) TCID(50) (median tissue culture infectious dose) of each of the three recommended 1997-1998 influenza vaccine components, A/Shenzhen/227/95 (H1N1) (A/Bayern/7/95 (H1N1)-like strain), A/Wuhan/359/95 (H3N2), and B/Ann Arbor/1/94 (B/Beijing/184/93-like strain). Two hundred and twenty-five healthy Australian children aged 12-42 months were enrolled and randomized in a 3:2 ratio to receive CAIV-T blended and filled either at Medeva or at Aviron-PA. Two doses of CAIV-T were given 4-6 weeks apart as an intranasal spray. Three blood specimens were collected (immediately before doses one and two, and 28 +/- 5 days following dose two) for measuring hemagglutination inhibition (HAI) antibody responses. Adverse events occurring within 10 days and serious adverse events occurring within 42 days were collected. Serum HAI antibody levels were measured against the three vaccine strains. Equivalent immunogenicity between the two vaccine groups was pre-specified as: (1) within 20% difference in seroconversion rates (HAI titers > or =4-fold rise); and (2) within 4-fold difference in the 90% confidence interval of geometric mean titer ratio. Among 10 pre-specified adverse events, only vomiting had significantly different incidence rates in the two vaccine groups following dose one (3% versus 13%, P = 0.01) but the difference disappeared following dose two (4% versus 4%). Differences in seroconversion rates following dose two between the two vaccine groups in pre-vaccination seronegative children were all <20% for the three vaccine strains (16% for H1N1, 0% for H3N2, and 0% for B). The results indicate that CAIV-T blended and filled in the two facilities had equivalent profiles of safety and immunogenicity.