Presence of defective viral genes in H1N1 live attenuated influenza vaccine strains is not associated with reduced human cell fitness or vaccine effectiveness

An Optimised Live Attenuated Influenza Vaccine Ferret Efficacy Model Successfully Translates H1N1 Clinical Data

Between 2013 and 2016, the A/H1N1pdm09 component of the live attenuated influenza vaccine (LAIV) produced instances of lower-than-expected vaccine effectiveness. Standard pre-clinical ferret models, using a human-like vaccine dose and focusing on antigenic match to circulating wildtype (wt) strains, were unable to predict these fluctuations. By optimising the vaccine dose and utilising clinically relevant endpoints, we aimed to develop a ferret efficacy model able to reproduce clinical observations. Ferrets were intranasally vaccinated with 4 Log10 FFU/animal (1000-fold reduction compared to clinical dose) of seven historical LAIV formulations with known (19-90%) H1N1 vaccine efficacy or effectiveness (VE). Following homologous H1N1 wt virus challenge, protection was assessed based on primary endpoints of wt virus shedding in the upper respiratory tract and the development of fever. LAIV formulations with high (82-90%) H1N1 VE provided significant protection from wt challenge, while formulations with reduced (19-32%) VE tended not to provide significant protection. The strongest correlation observed was between reduction in wt shedding and VE (R2 = 0.75). Conversely, serum immunogenicity following vaccination was not a reliable indicator of protection (R2 = 0.37). This demonstrated that, by optimisation of the vaccine dose and the use of non-serological, clinically relevant protection endpoints, the ferret model could successfully translate clinical H1N1 LAIV VE data.

Awareness and Uptake of COVID-19 Vaccines Among the Residents of Bisha in Saudi Arabia

OBJECTIVE

 Even though COVID-19 is no longer in an acute pandemic phase, sustaining awareness and promoting the uptake of COVID-19 vaccines are crucial for preventing future outbreaks and protecting public health. This study explores the awareness and uptake of COVID-19 vaccines among residents of Bisha, Asir province. It examines sources of information, healthcare providers' influence, and community engagement initiatives. The findings can inform future public health policies and strategies, supporting efforts to control the spread of the pandemic and enhance community resilience.

METHODS

 The cross-sectional study was administered to the adult population in Bisha. The study involved a total of 220 respondents. Data were collected using a questionnaire and analyzed using SPSS version 27 to obtain essential insights.

RESULTS

Most respondents (n = 204, 92.73%) reported receiving information about COVID-19 vaccines from healthcare professionals, other people, and family members. The study also revealed that only 46 (20.9%) individuals had exposure to COVID-19, with 36 (78.26%) reporting infection before vaccination and only 10 (21.74%) reporting infection after vaccination. Regarding COVID-19 vaccine first-dose uptake, less than half (27.73%) of the respondents had received the first dose. Among those who took the first dose, 29 (47.54%) took the second dose, while 32 (52.46%) did not. It also shows a statistically significant difference in COVID-19 vaccine uptake based on the participant's age, gender, education level, comorbidity, smoking status, and place of residence (P < 0.05).

CONCLUSION

There was a significantly high level of awareness about the vaccine, with significant proportions of respondents indicating their willingness to take preventive measures even after vaccination. However, vaccine uptake remains below optimal levels, with various reasons cited for non-vaccination, including concerns about vaccine availability, efficacy, and side effects. Healthcare professionals should intensify public education efforts and ensure the availability of vaccines in various forms at hospitals to address this issue.

Defective Interfering Particles of Influenza Virus and Their Characteristics, Impacts, and Use in Vaccines and Antiviral Strategies: A Systematic Review

Defective interfering particles (DIPs) are particles containing defective viral genomes (DVGs) generated during viral replication. DIPs have been found in various RNA viruses, especially in influenza viruses. Evidence indicates that DIPs interfere with the replication and encapsulation of wild-type viruses, namely standard viruses (STVs) that contain full-length viral genomes. DIPs may also activate the innate immune response by stimulating interferon synthesis. In this review, the underlying generation mechanisms and characteristics of influenza virus DIPs are summarized. We also discuss the potential impact of DIPs on the immunogenicity of live attenuated influenza vaccines (LAIVs) and development of influenza vaccines based on NS1 gene-defective DIPs. Finally, we review the antiviral strategies based on influenza virus DIPs that have been used against both influenza virus and SARS-CoV-2. This review provides systematic insights into the theory and application of influenza virus DIPs.

Roles for Pathogen Interference in Influenza Vaccination, with Implications to Vaccine Effectiveness (VE) and Attribution of Influenza Deaths

Pathogen interference is the ability of one pathogen to alter the course and clinical outcomes of infection by another. With up to 3000 species of human pathogens the potential combinations are vast. These combinations operate within further immune complexity induced by infection with multiple persistent pathogens, and by the role which the human microbiome plays in maintaining health, immune function, and resistance to infection. All the above are further complicated by malnutrition in children and the elderly. Influenza vaccination offers a measure of protection for elderly individuals subsequently infected with influenza. However, all vaccines induce both specific and non-specific effects. The specific effects involve stimulation of humoral and cellular immunity, while the nonspecific effects are far more nuanced including changes in gene expression patterns and production of small RNAs which contribute to pathogen interference. Little is known about the outcomes of vaccinated elderly not subsequently infected with influenza but infected with multiple other non-influenza winter pathogens. In this review we propose that in certain years the specific antigen mix in the seasonal influenza vaccine inadvertently increases the risk of infection from other non-influenza pathogens. The possibility that vaccination could upset the pathogen balance, and that the timing of vaccination relative to the pathogen balance was critical to success, was proposed in 2010 but was seemingly ignored. Persons vaccinated early in the winter are more likely to experience higher pathogen interference. Implications to the estimation of vaccine effectiveness and influenza deaths are discussed.

HA and M2 sequences alter the replication of 2013-16 H1 live attenuated influenza vaccine infection in human nasal epithelial cell cultures

From 2013 to 2016, the H1N1 component of live, attenuated influenza vaccine (LAIV) performed very poorly in contrast to the inactivated influenza vaccine. We utilized a primary, differentiated human nasal epithelial cell (hNEC) culture system to assess the replication differences between isogenic LAIVs containing the HA segment from either A/Bolivia/559/2013 (rBol), which showed poor vaccine efficacy, and A/Slovenia/2903/2015 (rSlov), which had reasonable vaccine efficacy. There were minimal differences in infectious virus production in Madin-Darby Canine Kidney (MDCK) cells, but the rSlov LAIV showed markedly improved replication in hNEC cultures at both 32 °C and 37 °C, demonstrating that the HA segment alone could impact LAIV replication in physiologically relevant systems. The rSlov-infected hNEC cultures showed stronger production of interferon and proinflammatory chemokines which might also be contributing to the increased overall vaccine effectiveness through enhanced recruitment and activation of immune cells. An M2-S86A mutation had no positive effects on H1 LAIV replication in hNEC cultures, in contrast to the increased infectious virus production seen in an H3 LAIV. No obvious defects in viral RNA packaging were detected, suggesting that HA function, rather than defective particle production, may be driving the differential infectious virus production in hNEC cultures. Overall, we have shown that not all H1 HA segments can be successfully used in LAIV, and this phenotype cannot be fully explained by segment incompatibilities. Physiologically relevant temperatures and primary cell cultures should be used to demonstrate that candidate LAIVs can replicate efficiently, which is a necessary property for effective vaccines.