Hemagglutination Inhibition Geometric Mean Titers Research Articles

Safety and immunogenicity of high-dose trivalent inactivated influenza vaccine in adults 50–64 years of age

BackgroundIndividuals 50–64 years of age have reduced immune responses to influenza vaccines. The current study examined whether a high-dose inactivated trivalent influenza vaccine (IIV3-HD) might improve immune responses over a standard-dose inactivated influenza vaccine (IIV3-SD) in this age group. MethodsThis was a multicenter, observer-blinded, randomized, active-controlled phase II trial. Adults 50–64 years of age were randomized 1:1 to receive IIV3-HD or IIV3-SD. Hemagglutination inhibition titers were measured before and 28 days after vaccination. Reactogenicity was recorded for 7 days after vaccination and adverse events for 28 days. Results148 participants received IIV3-HD and 152 received IIV3-SD. For all vaccine strains, day 28 geometric mean hemagglutination inhibition titers were significantly higher in the IIV3-HD group than in the IIV3-SD group (geometric mean titer ratio [95% confidence interval (CI)]=1.43 [1.04–1.97] for A/H1N1, 1.65 [1.21–2.25] for A/H3N2, and 1.60 [1.23–2.08] for B). Seroconversion rates were significantly higher in the IIV3-HD group than in the IIV3-SD group for strains A/H3N2 and B but not A/H1N1 (difference [95% CI]=13.5% [4.76–22.0] for A/H3N2, 23.1% [11.7–33.6] for B, and −0.2% [−9.66 to 9.18] for A/H1N1). The post-vaccination seroprotection rate was significantly higher in the IIV3-HD group than in the IIV3-SD group for strain B but not for strains A/H1N1 or A/H3N2 (difference=9.1% [2.95–15.7] for B, 2.0% [−0.907 to 5.68] for A/H1N1, and 0.6% [−3.14 to 4.43] for A/H3N2). Reactogenicity was higher in the IIV3-HD group than in the IIV3-SD group, but reactions were mostly of low intensity, transient, and self-limited. Rates of unsolicited adverse events were similar between groups. No serious AEs, AEs leading to early withdrawal, or deaths were reported. ConclusionsThe study suggests that in adults 50–64 years of age, IIV3-HD may improve immunogenicity compared to IIV3-SD while maintaining an acceptable safety profile.

Influenza Vaccination of Pregnant Women and Protection of Their Infants

Madhi SA, Cutland CL, Kuwanda L. Influenza vaccination of pregnant women and protection of their infants. N Engl J Med 2014; 371:918–31. Pregnant women are at risk for severe influenza from the second trimester to the early postpartum period, making them a priority group for seasonal influenza vaccination. Because pregnancy is characterized by the attenuation of cell-mediated immune responses, the efficacy of the inactivated influenza vaccine (IIV) in pregnant women may differ from that in nonpregnant women. Nevertheless, to date, no controlled trials have been performed to evaluate the efficacy of IIV during pregnancy. Furthermore, the vaccination of pregnant women may also confer partial protection against confirmed influenza in their infants. However, observational studies have had conflicting results with regard to the efficacy of the trivalent IIV during pregnancy in protecting infants against respiratory illness. The aim of this study was to evaluate the immunogenicity, safety, and efficacy of IIV in pregnant women and their infants until 24 weeks after birth. The authors performed 2 randomized, double-blind, placebo-controlled trials of trivalent IIV in pregnant women with and without human immunodeficiency virus (HIV). Healthy women aged 18 to 38 years with an estimated gestational age of 20 to 36 weeks were enrolled at 1 of 4 antenatal clinics in South Africa during the 2011 and 2012 influenza seasons. HIV-infected women who met these same eligibility criteria were enrolled during 2011. Participants were randomly assigned in a 1:1 ratio to receive IIV or placebo. Active surveillance for influenzalike illness was conducted through weekly contact with the participants. Women and infants identified as having influenza-like illness were tested for influenza virus by means of a reverse transcriptase–polymerase chain reaction (RT-PCR) assay. All the mothers and infants in the HIV-infected cohort and a nested group of uninfected mother–infant dyads were enrolled in an intensive safety and immunogenicity study. Those women were provided with diary cards on which to document for 1 week the possible local and systemic reactions to the vaccination, and blood samples were collected for hemagglutination inhibition (HAI) studies. A total of 2116 HIV-uninfected pregnant women were enrolled (mean age, 26.2 years; mean gestational age, 26.8 weeks) and gave birth to 2049 live infants. In the immunogenicity subset, seroconversion rates for strains A(H1N1), A(H3N2), and B(Victoria) among IIV recipients 1 month after immunization were 72.5%, 64.8%, and 92.3%, respectively; the rates among the placebo recipients were 8.1%, 2.7%, and 2.0%, respectively (P < .001 for all comparisons). Newborns of IIV recipients had higher HAI geometric mean titers for all the vaccine strains than did newborns of the placebo recipients, and they were also more likely to have an HAI titer of 1:40 or higher for A(H1N1) (81.1% vs 34.0%, respectively), A(H3N2) (60.0% vs 17.5%, respectively), and B (82.1% vs 43.7%, respectively) (P < .001 for all comparisons). The attack rate for RT-PCR–confirmed influenza among both the placebo recipients and their infants was 3.6%. The attack rates among IIV recipients and their infants were 1.8% and 1.9%, respectively, and the respective vaccine-efficacy rates were 50.4% (95% confidence interval [CI], 14.5–71.2) and 48.8% (95% CI, 11.6–70.4). A total of 194 HIV-infected women were included (mean maternal age, 28.2 years; mean gestational age, 27.3 weeks; baseline median CD4 T-cell count, 393.5 cells per μL; median level of plasma HIV-1 RNA, 1067 copies per milliliter). The attack rate for the placebo recipients was 17.0%, and the rate for IIV recipients was 7.0%; Literature Review

Safety and immunogenicity of a modified-vaccinia-virus-Ankara-based influenza A H5N1 vaccine: a randomised, double-blind phase 1/2a clinical trial

Modified vaccinia virus Ankara (MVA) is a promising viral vector platform for the development of an H5N1 influenza vaccine. Preclinical assessment of MVA-based H5N1 vaccines showed their immunogenicity and safety in different animal models. We aimed to assess the safety and immunogenicity of the MVA-haemagglutinin-based H5N1 vaccine MVA-H5-sfMR in healthy individuals. In a single-centre, double-blind phase 1/2a study, young volunteers (aged 18-28 years) were randomly assigned with a computer-generated list in equal numbers to one of eight groups and were given one injection or two injections intramuscularly at an interval of 4 weeks of a standard dose (10(8) plaque forming units [pfu]) or a ten times lower dose (10(7) pfu) of the MVA-H5-sfMR (vector encoding the haemagglutinin gene of influenza A/Vietnam/1194/2004 virus [H5N1 subtype]) or MVA-F6-sfMR (empty vector) vaccine. Volunteers and physicians who examined and administered the vaccine were masked to vaccine assignment. Individuals who received the MVA-H5-sfMR vaccine were eligible for a booster immunisation 1 year after the first immunisation. Primary endpoint was safety. Secondary outcome was immunogenicity. The trial is registered with the Dutch Trial Register, number NTR3401. 79 of 80 individuals who were enrolled completed the study. No serious adverse events were identified. 11 individuals reported severe headache and lightheadedness, erythema nodosum, respiratory illness (accompanied by influenza-like symptoms), sore throat, or injection-site reaction. Most of the volunteers had one or more local (itch, pain, redness, and swelling) and systemic reactions (rise in body temperature, headache, myalgia, arthralgia, chills, malaise, and fatigue) after the first, second, and booster immunisations. Individuals who received the 10(7) dose had fewer systemic reactions. The MVA-H5-sfMR vaccine at 10(8) pfu induced significantly higher antibody responses after one and two immunisations than did 10(7) pfu when assessed with haemagglutination inhibition geometric mean titre at 8 weeks against H5N1 A/Vietnam/1194/2004 (30·2 [SD 3·8] vs 9·2 [2·3] and 108·1 [2·4] vs 15·8 [3·2]). 27 of 39 eligible individuals were enrolled in the booster immunisation study. A single shot of MVA-H5-sfMR 10(8) pfu prime immunisation resulted in higher antibody responses after the booster immunisation than did two shots of MVA-H5-sfMR at the ten times lower dose. The MVA-based H5N1 vaccine was well tolerated and immunogenic and therefore the vaccine candidates arising from the MVA platform hold great promise for rapid development in response to a future influenza pandemic threat. However, the immunogenicity of this vaccine needs to be compared with conventional H5N1 inactivated non-adjuvanted vaccine candidates in head-to-head clinical trials. European Research Council.

Enhanced and persistent antibody response against homologous and heterologous strains elicited by a MF59®-adjuvanted influenza vaccine in infants and young children

BackgroundNon-adjuvanted seasonal influenza vaccines show only modest efficacy in young children. This study compared the immunogenicity, reactogenicity and safety of the MF59®-adjuvanted trivalent subunit vaccine (aTIV) with two non-adjuvanted trivalent vaccines, TIV-1, the non-adjuvanted version of aTIV, and TIV-2, a split virion vaccine. Methods6078 children received two doses of aTIV (n=3125), TIV-1 (n=1479), or TIV-2 (n=1474) four weeks apart (Days 1 and 29). Children aged 6 to <36 months and 36 to <72 months received 0.25mL and 0.50mL doses, respectively. Immunogenicity was assessed by hemagglutination inhibition (HI) assay (n=2435) on Days 1, 29, 50 and 209. Safety was assessed up to Day 394. ResultsAfter the second vaccination (Day 50), the aTIV group showed significantly higher geometric mean HI titers and seroconversion rates than the TIV-1 or TIV-2 groups against all homologous and heterologous strains. The difference was enhanced at HI titers ≥110. aTIV elicited a faster, more persistent antibody response, with significantly higher titers in the aTIV group after one vaccination (Day 29) and after six months (Day 209) than in either TIV group. aTIV was more reactogenic than were TIV-1 and TIV-2 but rates of severe adverse events were very low for all three vaccines. ConclusionIn infants and young children, the MF59-adjuvanted vaccine induced substantially faster (after one dose), higher, persistent HI titers than the non-adjuvanted vaccines, with consistently higher seroprotection rates at increased threshold HI titers.This trial is registered at clinicaltrials.gov: NCT01346592.

Nine μg intradermal influenza vaccine and 15 μg intramuscular influenza vaccine induce similar cellular and humoral immune responses in adults

Intanza® 9 μg (Sanofi Pasteur), a trivalent split-virion vaccine administered by intradermal (ID) injection, was approved in Europe in 2009 for the prevention of seasonal influenza in adults 18 to 59 years. Here, we examined the immune responses induced in adults by the ID 9 μg vaccine and the standard trivalent intramuscular (IM) vaccine (Vaxigrip® 15 μg, Sanofi Pasteur). This trial was a randomized, controlled, single-center, open-label study in healthy adults 18 to 40 years of age during the 2007/8 influenza season. Subjects received a single vaccination with the ID 9 μg (n = 38) or IM 15 μg (n = 42) vaccine. Serum, saliva, and peripheral blood mononuclear cells were collected up to 180 days post-vaccination.Geometric mean hemagglutination inhibition titers, seroprotection rates, seroconversion rates, and pre-vaccination-to-post-vaccination ratios of geometric mean hemagglutination inhibition titers did not differ between the two vaccines. Compared with pre-vaccination, the vaccines induced similar increases in vaccine-specific circulating B cells at day 7 but did not induce significant increases in vaccine-specific memory B cells at day 180. Cell-mediated immunity to all three vaccine strains, measured in peripheral blood mononuclear cells, was high at baseline and not increased by either vaccine. Neither vaccine induced a mucosal immune response. These results show that the humoral and cellular immune responses to the ID 9 μg vaccine are similar to those to the standard IM 15 μg vaccine.

Cellular and Humoral Immune Responses to Influenza Vaccine in SOT Recipients After Thymoglobulin or Basiliximab Induction.

Antibody responses to influenza vaccine are suboptimal in SOT recipients due to immunosuppression. We assessed both humoral and cellular responses after influenza vaccination in a cohort of SOT recipients receiving induction therapy with either basiliximab (BSX) or thymoglobulin (Thymo). During the 2012-2013 influenza season patients were vaccinated with the trivalent inactivated influenza vaccine. Blood was collected before and 6 weeks after vaccination. A hemagglutination inhibition (HI) assay was used to assess the humoral response. Seroprotection was defined as a titer ≥40 after vaccination. T-cell responses were assessed by IFN-γ Elispot and by flow cytometry with ICS for IFN-γ, IL-2, and TNF-α. 66 patients (61 kidney, 5 heart) were included (BSX n=39, Thymo n=27). Clinical baseline characteristics were similar between groups. Median time from transplant to vaccination was 31 months for BSX and 22 months for Thymo groups (p=0.24). CD4+ T-cell counts were lower in the Thymo than in the BSX group (307 c/mm3 vs. 673 c/mm3, p<0.001). After vaccination, HI geometric mean titers in the BSX vs. Thymo groups were 53 vs. 55 for H1N1 (p=0.92), 145 vs. 162 for H3N2 (p=0.59) and 11 vs. 28 for B strains (p=0.005). Seroprotective levels were achieved in 62% vs. 56% for H1N1 (p=0.79), 100% vs 100% for H3N2 (p=1.0) and 18% vs. 52% for B (p=0.006). By IFN-γ Elispot, the mean SFU/10e6 PBMC were comparable between the two groups (103 BSX vs. 107 Thymo, p=0.90). Increase of ≥2 times in the number of SFU were seen in 44% in the BSX vs. 52% in the Thymo groups (p=0.61). By ICS (n=51), multifunctional T-cell responses producing all 3 cytokines (IFN+, IL2+, TNF+) were not significantly different between the two groups (p=0.34). Similar results were observed in patients vaccinated during the first year post transplant (n=20). No correlation was noted between HI titers and IFN-γ spots (r=-0.092, p=0.46). No influenza or acute rejection occurred within 6 months post vaccination. Despite differences in CD4+ T-cells at baseline, the induction therapy regimen (BSX vs. Thymo) did not affect the global antibody and multifunctional T-cell responses of SOT recipients to influenza vaccine. Surprisingly, antibody responses to influenza B in the Thymo group were higher than those observed in the BSX group.

Vitamin E, vitamin A, and zinc status are not related to serologic response to influenza vaccine in older adults: an observational prospective cohort study

It has been hypothesized that micronutrient levels play a role in the immune response to vaccination; however, population-level research on the association between micronutrient levels and immune response to influenza vaccination is needed. In this study, we hypothesized that decreasing levels of nutrients would be associated with decreased hemagglutination inhibition (HAI) responses to influenza vaccination. Therefore, the purpose of this study was to determine whether serum vitamin A, vitamin E, or zinc levels are associated with influenza vaccine response determined by HAI titer in adults 65 years or older. Participants in this study included 205 community-dwelling adults 65 years or older who resided in Marshfield, WI, USA, from fall 2008 through spring 2009. Participants received trivalent influenza vaccine and donated blood samples before and 21 to 28 days after vaccination. Prevaccination levels of serum retinol, α-tocopherol, and zinc as well as prevaccination and postvaccination HAI titer levels were measured. No participants were vitamin A or vitamin E deficient; 20% had low serum zinc levels (<70 μg/dL). Continuous variables and categorical quartiles coding for vitamin A, vitamin E, and zinc levels were not related to prevaccination or postvaccination seroprotection or seroconversion for any of the vaccine components (influenza A [H1N1], A [H3N2], or B), after adjusting for age, sex, body mass index, and prevaccination HAI geometric mean titer. In conclusion, our study population showed no association between variations in levels of serum vitamin A, vitamin E, or zinc and influenza vaccine response as measured by HAI in adults older than 65 years. Thus, associations between micronutrients and other measures of vaccine response, such as cell-mediated immune parameters, should also be explored.

The Safety and Immunogenicity of Trivalent Inactivated Influenza Vaccination: A Study of Maternal-Cord Blood Pairs in Taiwan

BackgroundThere are little data about adverse effects and immunogenicity of flu vaccine in Asian pregnant women.MethodsThis prospective trial (NCT01514708) enrolled 46 pregnant women who received a single intramuscular dose of trivalent flu vaccine (AdimFlu-S®) containing 15 mcg of hemagglutinin for each strain/0.5 mL from influenza A (H1N1), influenza A (H3N2), and influenza B after the first trimester. Blood samples were collected at day 0 and 28 after vaccination, and at delivery. Cord blood was also collected. Hemagglutination inhibition (HAI) assays were performed to determine seroprotection and seroconversion rates and fold increase in the HAI geometric mean titer (GMT).ResultsTwenty-eight days after vaccination the seroprotection rate against H1N1, H3N2, and influenza B was 91.3%, 84.8% and 56.5%, respectively. The GMT fold increase was 12.8, 8.4, and 4.6 for H1N1, H3N2, and influenza B, respectively. At delivery, both the seroprotection rate (86.4%, 68.2%, and 47.7%) and GMT fold increase (9.4, 5.7 and 3.8) were slightly lower than day 28. The seroprotection rate and GMT fold increase in maternal and cord blood samples were comparable. No significant adverse effects were detected.ConclusionsTrivalent flu vaccine induces a strong immune response in pregnant women and their infants without adverse effects.Trial RegistrationClinical Trials. gov NCT01514708

Safety and immunogenicity of an oral, replicating adenovirus serotype 4 vector vaccine for H5N1 influenza: a randomised, double-blind, placebo-controlled, phase 1 study

SummaryBackgroundReplication-competent virus vector vaccines might have advantages compared with non-replicating vector vaccines. We tested the safety and immunogenicity of an oral adenovirus serotype 4 vector vaccine candidate (Ad4-H5-Vtn) expressing the haemagglutinin from an avian influenza A H5N1 virus.MethodsWe did this phase 1 study at four sites in the USA. We used a computer-generated randomisation list (block size eight, stratified by site) to assign healthy volunteers aged 18–40 years to receive one of five doses of Ad4-H5-Vtn (107 viral particles [VP], 108 VP, 109 VP, 1010 VP, 1011 VP) or placebo (3:1). Vaccine or placebo was given on three occasions, about 56 days apart. Participants, investigators, and study-site personnel were masked to assignment throughout the study. Subsequently, volunteers received a boost dose with 90 μg of an inactivated parenteral H5N1 vaccine. Primary immunogenicity endpoints were seroconversion by haemagglutination-inhibition (HAI), defined as a four-times rise compared with baseline titre, and HAI geometric mean titre (GMT). We solicited symptoms of reactogenicity daily for 7 days after each vaccination and recorded symptoms that persisted beyond 7 days as adverse events. Primary analysis was per protocol. This trial is registered with ClinicalTrials.gov, number NCT01006798.FindingsWe enrolled 166 participants (125 vaccine; 41 placebo) between Oct 19, 2009, and Sept 9, 2010. HAI responses were low: 13 of 123 vaccinees (11%, 95% CI 6–17) and three of 41 placebo recipients (7%, 2–20) seroconverted. HAI GMT was 6 (95% CI 5–7) for vaccinees, and 5 (5–6) for placebo recipients. However, when inactivated H5N1 vaccine became available, one H5N1 boost was offered to all participants. In this substudy, HAI seroconversion occurred in 19 of 19 participants in the 1011 VP cohort (100%; 95% CI 82–100) and eight of 22 placebo recipients (36%; 17–59); 17 of 19 participants in the 1011 VP cohort (89%; 67–99) achieved seroprotection compared with four of 22 placebo recipients (18%; 5–40); GMT was 135 (89–205) with 1011 VP, compared with 13 (7–21) with placebo. The cumulative frequency of abdominal pain, diarrhoea, and nasal congestion after all three vaccinations was significantly higher in vaccinees than placebo recipients (21 [16·8%] of 125 vs one [2·4%] of 41, p=0·017; 24 [19·2%] of 125 vs two [4·9%] of 41, p=0·027; 41 [32·8%] of 125 vs six [14·6%] of 41, p=0·028; respectively). No serious treatment-related adverse events occurred.InterpretationOral Ad4 vector priming might enhance the efficacy of poorly immunogenic vaccines such as H5N1.FundingWellcome Trust Foundation, PaxVax.

The Madin-Darby canine kidney cell culture derived influenza A/H5N1 vaccine: A Phase I trial in Taiwan

Avian H5N1 influenza has caused human infections globally and has a high mortality rate. Rapid production of effective vaccines is needed. A phase 1, randomized, observer-blinded clinical trial was conducted to examine the safety and immunogenicity of an inactivated whole virion vaccine against the influenza A/H5N1 virus produced from the Madin-Darby canine kidney (MDCK) cell line. Participants were randomized to four groups and administered two intramuscular doses of vaccine containing 3 μg hemagglutinin (HA), 3 μg HA with 300 μg aluminum phosphate (AlPO4), 6 μg HA, and 6 μg HA with 300 μg AlPO4, respectively, at two visits, 21 days apart. Serum hemagglutination inhibition (HAI) and neutralizing antibody levels were determined at baseline and on Days 21 and 42. Sixty healthy individuals were enrolled. The neutralization assay showed a significant immune response in the 6 μg with ALPO4 group on Day 42 compared to pre-vaccination levels (11.32±9.77 vs. 4.00±0, p=0.02). The adjuvant effect in neutralization assay was also significant on Day 42 in the 6 μg group (4.52±1.94 without adjuvant vs. 11.32±9.77 with adjuvant, p=0.02). HAI assay also showed an aluminum adjuvant-induced increasing trend in HAI geometric mean titer on Day 42 in the 3 μg and 6 μg groups (6.02 versus 8.20, p=0.05 and 5.74 versus 8.21, p=0.14). The most frequent adverse event was local pain (20% to 60%). There were no vaccine-related severe adverse effects. MDCK cell line-derived H5N1 vaccine was well tolerated. It is necessary to investigate further the immunogenicity of higher antigen doses and the role of aluminum adjuvant in augmenting the effect of the vaccine.

Compatibility of ASO3-adjuvanted H1N1pdm09 and seasonal trivalent influenza vaccines in adults: Results of a randomized, controlled trial

When Canada chose a novel adjuvanted vaccine to combat the 2009 influenza pandemic, seasonal trivalent inactivated vaccine (TIV) was also available but compatibility of the two had not been assessed. To compare responses after concurrent or sequential administration of these vaccines, adults 20–59 years old were randomly assigned (1:1) to receive ASO3-adjuvanted H1N1pdm09 vaccine (Arepanrix®, GSK, Quebec City, Quebec), with TIV (Vaxigrip®, Sanofi Pasteur, Toronto) given concurrently or 21 days later. Blood was obtained at baseline and 21 days after each vaccination to measure hemagglutination inhibition (HAI) titers. Adverse effects were assessed using symptom diaries and personal interviews. 282 participants completed the study (concurrent vaccines 145, sequential vaccines 137). HAI titers to H1N1pdm09 were ≥40 at baseline in 15–18% of participants and following vaccination in 91–92%. Initially seropositive subjects (titer ≥10) had lower H1N1pdm09 geometric mean HAI titers (GMT) after concurrent than separate vaccinations (320.0 vs 476.5, p=0.039) but both exceeded GM responses of initially naïve participants, which were unaffected by concurrent TIV. Responses to TIV were not lower after concurrent than separate vaccination. Adverse event rates were not increased by concurrent vaccinations above those with H1N1pdm09 vaccine alone. This adjuvanted H1N1pdm09 vaccine was immunogenic and compatible with concurrently administered TIV.

Higher Antigen Content Improves the Immune Response to 2009 H1N1 Influenza Vaccine in HIV-Infected Adults: A Randomized Clinical Trial

The immunogenicity of a high hemagglutinin (HA) dose or a second dose of influenza vaccine in human immunodeficiency virus (HIV)-infected individuals has not been fully explored. One hundered ninety-two HIV-infected individuals aged 18-64 years were stratified by CD4 cell count (<200 cells/mL or ≥200 cells/mL) and randomized to receive 2 doses of 15 μg or 30 μg HA 2009 H1N1 vaccine 21 days apart. Hemagglutination inhibition (HAI) and microneutralization (MN) antibodies were measured on days 0, 10, 21, 31, 42, and 201. Recipients of 30 μg HA had significantly higher HAI geometric mean titers (GMTs), compared with recipients of 15 μg HA on days 10 (139.0 vs 51.9; P = .01), 21 (106.7 vs 51.9; P = .001), and 31 (130.0 vs 73.7; P = .03) but not on days 42 (91.8 vs 61.6; P = .11) and 201 (43.0 vs 27.0; P = .08). When analyzed by CD4 cell count stratum, HAI GMTs were significantly higher among 30 μg HA recipients than among 15 μg HA in the CD4 cell count <200 cells/mL stratum on days 21 and 31 and the MN GMTs on days 10, 21, 31, and 42 (P < .05). In the CD4 cell count ≥200 cells/mL stratum, MN GMTs were significantly higher among recipients of 30 μg HA than among recipients of 15 μg HA on day 10 (P = .03). Increasing the HA dose of the 2009 H1N1 vaccine improves the vaccine's immunogenicity in HIV-infected individuals. NCT00992433.

Safety, tolerability, and immunogenicity of inactivated trivalent seasonal influenza vaccine administered with a needle-free disposable-syringe jet injector

Jet injectors (JIs) avoid safety drawbacks of needle-syringe (N-S) while generating similar immune responses. A new generation of disposable-syringe jet injectors (DSJIs) overcomes the cross-contamination risk of multi-use-nozzle devices used in 20th-century campaigns. In the first study in humans, the newly-US-licensed LectraJet(®) model M3 RA DSJI was compared to N-S. Sixty healthy adults received one 0.5 mL intramuscular dose of the 2009-2010 seasonal, trivalent, inactivated influenza vaccine (TIV) in randomized, double-masked fashion by either DSJI (n=30) or N-S (n=30). Adverse reactions were monitored for 90 days after injection, and serologic responses assayed by hemagglutination inhibition (HI) at days 28 and 90. There were no related serious adverse events (SAEs), nor differing rates of unsolicited AEs between DSJI and N-S. Solicited erythema and induration occurred more often after DSJI, but were transient and well-tolerated; a trend was noted for fewer systemic reactions by DSJI. Pre-vaccination HI geometric mean titers (GMT) increased by 28 days for H1N1, H3N2, and B antigens by 13-, 14-, and 8-fold via DSJI, and by 7-, 10-, and 7-fold for N-S, respectively. No trending differences in GMT, seroconversion, or seroprotection were noted; sample sizes precluded non-inferiority assessment. DSJI delivery of TIV is well-tolerated and immunogenic.

Safety and immunogenicity of a virus-like particle pandemic influenza A (H1N1) 2009 vaccine in a blinded, randomized, placebo-controlled trial of adults in Mexico

Virus-like particles (VLPs) can be rapidly developed from influenza virus genetic sequences in order to supply vaccine after the onset of a pandemic. The safety and immunogenicity of one or two doses of a recombinant A (H1N1) 2009 influenza VLP vaccine was evaluated in a two-stage, Phase 2, randomized, double-blind, placebo-controlled study conducted in 4563 healthy adults, 18–64 years of age, during the H1N1 2009 pandemic in Mexico. In Part A, 1013 subjects were randomized into four treatment groups (5μg, 15μg, or 45μg hemagglutinin [HA] VLP vaccine or placebo) and vaccinated 21 days apart, with sera collected on Days 1, 14 and 36 for hemagglutination inhibition (HAI) testing. After review of safety and immunogenicity data from Part A, additional subjects were immunized with a single dose of 15μg VLP vaccine (N=2537) or placebo (N=1011) and assessed for safety in Part B. Results showed the H1N1 2009 VLP vaccine was safe and well-tolerated. Systemic solicited events were similar between placebo and VLP vaccinated groups with no vaccine-related serious adverse events. Dose response trends for solicited local adverse events were observed, with higher incidences of local pain, swelling, tenderness, and redness reported in the higher VLP dose groups (15μg and 45μg) compared to the placebo and 5μg VLP groups following both vaccinations. Although the majority of local AEs were mild in severity, a dose trend in events of moderate or greater severity was also noted for these solicited events. The VLP vaccine groups demonstrated robust HAI immune responses after a single vaccination, with high rates of seroprotection (≥40 HAI titer) in 82–92% of all subjects and in 64–85% of subjects who were seronegative at the time of immunization. HAI geometric mean titers (GMTs), geometric mean ratios (GMRs) and seroconversion rates were also all statistically higher in the VLP groups compared to placebo for both post-baseline time points. Based on these data, additional clinical trials are in development to evaluate influenza vaccine candidate antigens manufactured using Spodoptera frugiperda (Sf9)/baculovirus-based VLP technology.

Mycoplasma gallisepticum experimental infection and tissue distribution in chickens, sparrows and pigeons

The most effective approaches to control the spread of Mycoplasma gallisepticum include strict biosecurity measures, continuous surveillance and eradication of infected flocks. The rapid expansion of the poultry industry worldwide in restricted geographical areas and severe economic losses due to M. gallisepticum outbreaks make it crucial to identify and better control the vectors responsible for the transmission of the disease. In the present study we evaluated the susceptibility of sparrows and pigeons to M. gallisepticum and the tissue distribution of M. gallisepticum in these species as compared with chickens. This information will further define the role of these common avian species in M. gallisepticum transmission. Twenty-six chickens, pigeons, and sparrows were experimentally inoculated with a field strain of M. gallisepticum and were monitored for the development of clinical signs, seroconversion, productive infection by culture, and M. gallisepticum distribution in their tissues by immunohistochemistry. All M. gallisepticum-inoculated chickens showed mild respiratory signs, seroconverted (haemagglutination inhibition geometric mean titre = 494) and shed M. gallisepticum in their tracheas. M. gallisepticum antigens were observed at high levels by immunohistochemistry in their tracheas, conjunctivas, nasal turbinates, and air sacs. The pigeons and sparrows did not show clinical signs or seroconvert but M. gallisepticum was reisolated up to 7 days post inoculation from pigeons and intermittently from sparrows. M. gallisepticum antigens were observed at low level in the conjunctiva of some pigeons and sparrows, as well as in the trachea of some sparrows. We conclude that pigeons and sparrows are partially susceptible to M. gallisepticum infection but do not seroconvert or maintain a steady carrier state similar to chickens and that these species may play a role in M. gallisepticum transmission between poultry farms as mechanical vectors.

Immunogenicity and safety of inactivated influenza vaccines in primed populations: A systematic literature review and meta-analysis

Several inactivated influenza vaccine formulations for systemic administration in man are currently available for annual (seasonal) immunization: split virus and subunit (either plain-aqueous, or virosomal, or adjuvanted by MF59). From a literature search covering the period 1978–2009, 33 articles could be identified, which described randomized clinical trials comparing at least two of the four vaccine formulations with respect to serum hemagglutination inhibition (HI) antibody response, local and systemic vaccine reactions and serious adverse events after vaccination, and employing seasonal vaccine components and doses. In total, 9121 vaccinees of all ages, either healthy or with underlying diseases, were involved. Most vaccinees were primed or had been vaccinated in previous years. For immunogenicity, homologous post-vaccination geometric mean HI titers (GMTs) were analyzed by a random effects model for continuous data. Unreported standard deviations (SD) were addressed by imputing assumed SD-values. Age and health state of the vaccinees appeared to have little influence on the outcome. The immunogenicity of split, aqueous and virosomal subunit formulations were similar, with geometric mean ratio values (GMR, quotient of paired GMT-values) varying around one (0.93–1.24). The MF59-adjuvanted subunit vaccine induced, on average, larger antibody titers than the non-adjuvanted vaccine formulations, but the absolute increase was small (GMR-values varying between 1.25 and 1.40). Vaccine reactions were analyzed using a random effects model for binary data. Local and systemic reactogenicity was similar among non-adjuvanted formulations. The adjuvanted subunit formulation was more frequently associated with local reactions than the non-adjuvanted formulations (rate ratio: 2.12, significant). Systemic reactions were similar among all vaccine formulations. The original articles emphasized the mild and transient character of the vaccine reactions and the absence of serious vaccine-related adverse events. This adequate amount of evidence led to the conclusion that all the currently available inactivated influenza vaccine formulations are safe, well tolerated and similarly effective to control seasonal influenza outbreaks across primed populations and age ranges.

Effect on Cellular and Humoral Immune Responses of the AS03 Adjuvant System in an A/H1N1/2009 Influenza Virus Vaccine Administered to Adults during Two Randomized Controlled Trials

The influence of AS03(A), a tocopherol oil-in-water emulsion-based adjuvant system, on humoral and cell-mediated responses to A/California/7/2009 H1N1 pandemic vaccine was investigated. In two observer-blind studies, a total of 261 healthy adults aged 18 to 60 years were randomized to receive either AS03(A)-adjuvanted H1N1 vaccine containing 3.75 μg hemagglutinin (HA) or nonadjuvanted H1N1 vaccine containing 15 or 3.75 μg HA on days 0 and 21. Hemagglutination inhibition (HI) antibody and T-cell responses were analyzed up to day 42. A first dose of AS03(A)-adjuvanted vaccine (3.75 μg HA) or nonadjuvanted vaccine (15 μg HA) induced HI responses of similar magnitudes that exceeded licensure criteria (e.g., 94 to 100% with titers of ≥ 40). A lower response following 3.75 μg HA without adjuvant was observed (73% with titers of ≥ 40). Following a second dose, geometric mean HI titers at day 42 were higher for AS03(A)-adjuvanted vaccine (636 and 637) relative to nonadjuvanted vaccine (341 for 15 μg HA and 150 for 3.75 μg HA). Over the 42-day period, the increase in frequency of A/H1N1/2009-specific CD4⁺ T cells was significantly higher in the adjuvanted group than in the nonadjuvanted group. There was no evidence of correlation between baseline CD4⁺ T-cell frequencies and day 21 HI antibody titers, while there was some correlation (R = 0.35) between day 21 CD4⁺ T-cell frequencies and day 42 HI titers. AS03(A) adjuvant enhanced the humoral and CD4⁺ T-cell-mediated responses to A/H1N1/2009 vaccine. Baseline A/H1N1/2009-specific CD4⁺ T-cell frequencies did not predict post-dose 1 antibody responses, but there was some correlation between post-dose 1 CD4⁺ T-cell frequencies and post-dose 2 antibody responses.

Reduced immunogenicity of influenza vaccines in HIV-infected compared with uninfected pregnant women is associated with regulatory T cells

To evaluate the immunogenicity of influenza vaccines in HIV-infected pregnant women and the factors that may determine this response. Prospective, single-site study of HIV-infected and uninfected women. Pregnant women had the following immunologic measurements at vaccination, 6 weeks after immunization, and 12 weeks after delivery: hemagglutination inhibition (HAI) antibody titers, lymphocyte proliferation (LPA), interferon-γ enzyme-linked immunospot (ELISPOT), and polychromatic flow cytometric enumeration of influenza-specific effector and regulatory T cells. At vaccination, demographic and gestational characteristics did not differ significantly between the 20 HIV-infected and 18 uninfected participants. Prevaccination HAI geometric mean titers (GMTs) against all strains of influenza in the vaccines were similar between the two groups. Antibody responses to vaccination measured by GMT or four-fold titer increase were significantly lower in HIV-infected compared with uninfected pregnant women for influenza A strains. Antibody responses to influenza B were equally low in the two groups of participants. There were no significant LPA or ELISPOT responses to vaccination in either group. LPA results were significantly lower in HIV-infected compared with uninfected women at all time points, but ELISPOT were not. Influenza-specific regulatory CD4(+)FoxP3(+)% and CD4(+)IL10(+)% increased after vaccination in both groups, but significantly more in HIV-infected compared with uninfected pregnant women. Higher influenza-specific CD4(+)FoxP3(+)% postvaccination correlated with lower antibody responses to the vaccine and lower LPA results. Influenza vaccines have reduced immunogenicity in HIV-infected compared with uninfected pregnant women. In HIV-infected women, increased regulatory CD4(+)FoxP3(+)% may attenuate the immunogenicity of vaccines.

Transmission of influenza A viruses between pigs and people, Iowa, 2002–2004

Triple-reassortant (tr) viruses of human, avian, and swine origin, including H1N1, H1N2, and H3N2 subtypes, emerged in North American swine herds in 1998 and have become predominant. While sporadic human infections with classical influenza A (H1N1) and with tr-swine influenza viruses have been reported, relatively few have been documented in occupationally exposed swine workers (SW). We conducted a 2-year (2002-2004) prospective cohort study of transmission of influenza viruses between pigs and SW from a single pork production company in Iowa. Respiratory samples were collected and tested for influenza viruses from SW and from pigs under their care through surveillance for influenza-like illnesses (ILI). Serial blood samples from study participants were tested by hemagglutination inhibition (HI) for antibody seroconversion against human and swine influenza viruses (SIV), and antibody seroprevalence was compared to age-matched urban Iowa blood donors. During the first year, 15 of 88 SW had ILI and were sampled; all were culture-negative for influenza. During the second year, 11 of 76 SW had ILI and were sampled; one was culture-positive for a human seasonal H3N2 virus. Among 20 swine herd ILI outbreaks sampled, influenza A virus was detected by rRT-PCR from 17 with 11 trH1N1 and five trH3N2 virus isolates cultured. During both years, HI geometric mean titers were significantly higher among SW compared to blood donor controls for three SIV: classical swine Sw/WI/238/97 (H1N1), tr Sw/IN/9K035/99 (H1N2), and trSw/IA/H02NJ56371/02 (H1N1)] (P < 0·0001). SW had serologic evidence for infection with both swine and human influenza viruses and were exposed to diverse influenza virus strains circulating in pigs. Influenza virus surveillance among pigs and SW should be encouraged to better understand cross-species transmission and diversity of influenza viruses at the human-swine interface.

RAPID DEVELOPMENT OF A VAXFECTIN®-ADJUVANTED DNA VACCINE ENCODING PANDEMIC SWINE-ORIGIN INFLUENZA A VIRUS (H1N1) HEMAGGLUTININ

To support the initiation of a clinical trial in humans, the immunogenicity of a plasmid DNA vaccine encoding the hemagglutinin (HA) of the swine-origin influenza A (H1N1) virus (S-OIV) isolate, A/California/04/09, formulated with the adjuvant, Vaxfectin®, was administered intramuscularly to mice and rabbits at 100 μg and 1 mg DNA per injection, respectively, on Days 0 and 21. In hemagglutination inhibition (HI) assays using the reassortant virus, A/CA/07/09 NYMC X-179A, the titers for all animals were < 10 before vaccination. Three weeks after the first vaccination, 88% of mice and 75% of rabbits reached an HI titer of ≥ 40 with geometric mean titers (GMT) of 73 and 95, respectively. Two weeks after the second vaccination, 100% of mice and rabbits reached an HI titer of ≥ 40 with GMTs of 987 (range: 320–2560) for mice and 1522 (range: 640–2560) for rabbits. Sera from vaccinated mice and rabbits were also tested for HI titers against related S-OIV isolates. For mouse sera at Day 42, the HI GMTs against A/California/07/09, A/Texas/15/09 and A/Mexico/4108/09 were 905, 1280, and 1174, respectively, and for rabbit sera at Day 35 were 1522, 1280, and 1280, respectively. The results of this study indicate that the Vaxfectin®-adjuvanted S-OIV DNA vaccine is immunogenic and elicits HI antibodies that are reactive with related S-OIV.