A Phase 2 Clinical Trial to Evaluate the Safety, Reactogenicity, and Immunogenicity of Different Prime-Boost Vaccination Schedules of 2013 and 2017 A(H7N9) Inactivated Influenza Virus Vaccines Administered with and without AS03 Adjuvant in Healthy US Adults.

INTRODUCTION: A surge of human influenza A(H7N9) cases began in 2016 in China due to an antigenically distinct lineage. Data are needed about the safety and immunogenicity of 2013 and 2017 A(H7N9) inactivated influenza vaccines (IIVs) and the effects of AS03 adjuvant, prime-boost interval, and priming effects of 2013 and 2017 A(H7N9) IIVs. METHODS: Healthy adults (n=180), ages 19-50 years, were enrolled into this partially-blinded, randomized, multi-center Phase 2 clinical trial. Participants were randomly assigned to 1 of 6 vaccination groups evaluating homologous versus heterologous prime-boost strategies with two different boost intervals (21 versus 120 days) and two dosages (3.75 or 15 µg of hemagglutinin) administered with or without AS03 adjuvant. Reactogenicity, safety, and immunogenicity measured by hemagglutination inhibition (HAI) and neutralizing antibody titers were assessed. RESULTS: Two doses of A(H7N9) IIV were well tolerated, and no safety issues were identified. Although most participants had injection site and systemic reactogenicity, these symptoms were mostly mild to moderate in severity; injection site reactogenicity was greater in vaccination groups receiving adjuvant. Immune responses were greater after an adjuvanted second dose, and with a longer interval between prime and boost. The highest HAI GMT (95%CI) observed against the 2017 A(H7N9) strain was 133.4 (83.6, 212.6) among participants who received homologous, adjuvanted 3.75 ug+AS03/2017 doses with delayed boost interval. CONCLUSIONS: Administering AS03 adjuvant with the second H7N9 IIV dose and extending the boost interval to 4 months resulted in higher peak antibody responses. These observations can broadly inform strategic approaches for pandemic preparedness. (NCT03589807).

Immunogenicity and safety of varying dosages of a fifth-wave influenza A/H7N9 inactivated vaccine given with and without AS03 adjuvant in healthy adults.

BACKGROUND: Human infections with the avian influenza A(H7N9) virus were first reported in China in 2013 and continued to occur in annual waves. In the 2016/2017 fifth wave, Yangtze River Delta (YRD) lineage viruses, which differed antigenically from those of earlier waves, predominated. METHODS: In this phase 2 double-blinded trial we randomized 720 adults ≥ 19 years of age to receive two injections of a YRD lineage inactivated A/Hong Kong/125/2017 fifth-wave H7N9 vaccine, given 21 days apart, at doses of 3.75, 7.5, and 15 µg of hemagglutinin (HA) with AS03A adjuvant and at doses of 15 and 45 µg of HA without adjuvant. RESULTS: Two doses of adjuvanted vaccine were required to induce HA inhibition (HI) antibody titers ≥ 40 in most participants. After two doses of the 15 µg H7N9 formulation, given with or without AS03 adjuvant, the proportion achieving a HI titer ≥ 40 against the vaccine strain at 21 days after the second vaccination was 65 % (95 % CI, 57 %-73 %) and 0 % (95 % CI, 0 %-4%), respectively. Among those who received two doses of the 15 µg adjuvanted formulation the proportion with HI titer ≥ 40 at 21 days after the second vaccination was 76 % (95 % CI, 66 %-84 %) in those 19-64 years of age and 49 % (95 % CI, 37 %-62 %) in those ≥ 65 years of age. Responses to the adjuvanted vaccine formulations did not vary by HA content. Antibody responses declined over time and responses against drifted H7N9 strains were diminished. Overall, the vaccines were well tolerated but, as expected, adjuvanted vaccines were associated with more frequent solicited systemic and local adverse events. CONCLUSIONS: AS03 adjuvant improved the immune responses to an inactivated fifth-wave H7N9 influenza vaccine, particularly in younger adults, but invoked lower responses to drifted H7N9 strains. These findings may inform future influenza pandemic preparedness strategies.

Incident HIV Infection Among Young Men Associated With Female Sexual Partner Types Identified Through Latent Class Analysis, Rakai, Uganda.

BACKGROUND: Sexual partner characteristics are important determinants of HIV acquisition, but little is known about partner types of young men in sub-Saharan Africa. METHODS: Sexually active men aged 15-24 years from 5 rounds (2005-2013) of the Rakai Community Cohort Study in Uganda reported characteristics of up to 4 past-year female partners. Partner types were identified using latent class analysis. HIV incidence rates (IRs) were calculated by partner-type combinations, and individual-level risk adjusted IR ratios (aIRRs) relative to the lowest incidence type were estimated using the Poisson regression with generalized estimating equations. RESULTS: Young men (N = 1771) reported 4539 past-year female sexual partners. Three partner types were identified: type A: noncohabiting, student, medium duration partnerships; type B: cohabiting, nonstudent, longer duration partnerships; and type C: noncohabiting, nonstudent shorter duration partnerships. Type C partners engaged in the most HIV-related risk behaviors. Many men (29%) had more than 1 partner type/round. IR overall was 9.8/1000 person-years [95% confidence interval (CI): 4.7 to 20.6]. IR was 4.0 (95% CI: 1.2 to 12.7) for men with type A partners alone (41% of men). Relative to them, IR for those with type B partners alone (25%) was not significantly different. Men with type C partners alone (5%) had higher risk (aIRR = 3.2; 95% CI: 1.0 to 9.9), as did men with >1 partner type, including men with both type A and type B partners (12%; aIRR = 6.3; 95% CI: 2.5 to 15.9) and men with type C and other partner types (17%; aIRR = 4.3; 95% CI: 1.7 to 10.8). CONCLUSIONS: Partner-type combination was strongly associated with HIV incidence; type C partners and having more than 1 partner type were the riskiest patterns.