A Phase 1 Randomized Placebo-Controlled Study to Assess the Safety, Immunogenicity and Genetic Stability of a New Potential Pandemic H7N9 Live Attenuated Influenza Vaccine in Healthy Adults

Safety and Viral Shedding of Live Attenuated Influenza Vaccine (LAIV) in Chinese Healthy Juveniles and Adults: A Phase Ⅰ Randomized, Double-Blind, Placebo-Controlled Study

This study was a randomized, double-blind, placebo-controlled study to evaluate the safety and viral shedding of live attenuated influenza vaccine (LAIV) in Chinese healthy juveniles and adults. A total of 80 Eligible volunteers were divided into two age groups (≥18 and 3–17 years old). Volunteers were randomly and equally assigned to the experimental group and placebo-controlled group by ratio of 3:1 in each age group. Vaccination was carried out in steps. Totally, 34 (56.67%) adverse events and 24 (40.00%) adverse reactions of the LAIV group were reported. Most adverse reactions were grade 1 and grade 2, and the incidence of adverse reactions that grade 3 was 5%. The most common local reaction was runny nose/nasal congestion (n = 4, 6.67%). And the most common general reaction was fever (n = 10, 16.67%). There were no statistically significant differences in the incidence of total adverse reactions, different grades of adverse reactions, and symptoms between the experimental group and placebo-controlled group. No severe adverse events were reported. Three subjects (5.00%) had been detected vaccine strains on the 3rd day after LAIV vaccination; one was type B and the other two were H3N2. Four subjects (6.67%) had been detected with vaccine strains on the 7th day after LAIV vaccination, all were H3N2. There were no subjects detected carrying the influenza virus on the 15th day after vaccination. There were no statistically significant differences in the positive rate of vaccine strains of influenza virus between the experimental group and placebo-controlled group. The vaccine was well tolerated and not associated with increased rates in adverse reactions or the occurrence of severe adverse events. Pathogenicity of shed vaccine virus to surrounding people was not observed. Thus, Phase Ⅱ study can be carried out as scheduled.

Antigenic Characterization of Neuraminidase of Influenza A/H7N9 Viruses Isolated in Different Years

Influenza outbreaks caused by A/H7N9 viruses have occurred since 2013. After 2016, A/H7N9 influenza viruses underwent evolutionary changes. In this study, we examined the antigenic properties of influenza neuraminidase (NA) of A/H7N9 viruses as part of a live influenza vaccine (LAIV). It was shown that neuraminidase inhibiting (NI) antibodies obtained after A/Anhui/1/2013(H7N9)-based LAIV vaccination did not inhibit A/Hong Kong/125/2017(H7N9) NA and vice versa. The A/Hong Kong/125/2017(H7N9)-based LAIV elicited higher levels of NI antibodies compared to the A/Anhui/1/2013(H7N9)-based LAIV after two doses. Thelow degree of coincidence of the antibody response to hemagglutinin (HA) and NA after LAIV vaccination allows us to consider an enzyme-linked lectin assay (ELLA) as an additional measure for assessing the immunogenicity of influenza vaccines. In mice, N9-reactive monoclonal antibodies (mABs) for the A/environment/Shanghai/RL01/2013(H7N9) influenza virus partially protected against lung infection from the A/Guangdong/17SF003/2016 IDCDC-RG56N(H7N9) virus, thus showing the cross-protective properties of monoclonal antibodies against the drift variant.

Safety and Efficacy of Spray Intranasal Live Attenuated Influenza Vaccine: Systematic Review and Meta-Analysis

Although influenza is a major public health concern, little is known about the use of spray live attenuated influenza vaccine (LAIV) among adults. For this reason, we conducted a systematic review and meta-analysis to investigate the efficacy and safety of LAIV, especially in adults with/without clinical conditions and children <2 years, with the final aim of possibly extending the clinical indications. PubMed/MEDLINE and Scopus were the two databases consulted through February 2021. The Preferred Reporting Items for Systematic Reviews and Meta-Analyses guidelines were followed. A critical appraisal was conducted. Analyses were performed by using ProMeta3 software. Twenty-two studies were included, showing that LAIV was associated with a higher probability of seroconversion when compared with a placebo and considering the A/H1N1 serotype (pooled OR = 2.26 (95% CI = 1.12–4.54), p-value = 0.022; based on 488 participants, without heterogeneity (I2 = 0.0%)). The meta-analysis also confirmed no significant association with systemic adverse events. Only rhinorrhea, nasal congestion, and sore throat were significantly associated with LAIV compared to the placebo. Despite limited available evidence, LAIV has proved to be a safe and effective flu vaccination, also due to its very low invasiveness, and our review’s results can be considered a starting point for guiding future research and shaping forthcoming vaccination campaigns.