Immunity against influenza A(H1N1) infections is determined by age at the time of initial strain circulation

Post-vaccination serum cytokines levels correlate with breakthrough influenza infections

Post-vaccination cytokine levels from 256 young adults who subsequently suffered breakthrough influenza infections were compared with matched controls. Modulation within the immune system is important for eliciting a protective response, and the optimal response differs according to vaccine formulation and delivery. For both inactivated influenza vaccine (IIV) and live attenuated influenza vaccines (LAIV) lower levels of IL-8 were observed in post-vaccination sera. Post-vaccination antibody levels were higher and IFN-γ levels were lower in IIV sera compared to LAIV sera. Subjects who suffered breakthrough infections after IIV vaccination had higher levels of sCD25 compared to the control group. There were differences in LAIV post-vaccination interleukin levels for subjects who subsequently suffered breakthrough infections, but these differences were masked in subjects who received concomitant vaccines. Wide variances, sex-based differences and confounders such as concomitant vaccines thwart the establishment of specific cytokine responses as a correlate of protection, but our results provide real world evidence that the status of the immune system following vaccination is important for successful vaccination and subsequent protection against disease.

Seasonal burden of severe influenza virus infection in the critically ill patients, using the Assistance Publique-Hôpitaux de Paris clinical data warehouse: a pilot study

Purpose

At the critical care level, the flu surveillance system is limited in France, with heterogeneous regional modalities of implementation.

Materials, patients and methods

We aimed at assessing the relevance of the Assistance Publique-Hôpitaux de Paris (AP-HP) clinical data warehouse for estimating the burden of the influenza epidemic on medical adult critical care units of the AP-HP, and outcome of patients during the flu season 2017–2018. This exploratory multi-site epidemiological study comprised all consecutive adult stays (n = 320) in 18 medical intensive care units (ICU) or intermediate care wards (ICW) for probable or confirmed Influenza virus infection during the 2017–2018 flu season.

Results

Patients admitted to ICU/ICW had low vaccination coverage (21%), required life support in 60% of cases, stayed in the ICU for a median of 8 days, and had high 28-day mortality rate (19.7%; 95% confidence interval 15.5–24.5). Early prognostic factors included age, core temperature, the acute organ failures score, and the early administration of antiviral therapy.

Conclusions

Data directly extracted from the electronic medical records stored in the data warehouse provide detailed clinical, care pathway and prognosis information. The real-time availability should enable to detect and assess the burden of the most severe cases. By a firmer and more acute monitoring and adjustment of care and patient management, hospitals could generate more ICU/ICW capacities, sensitize their emergency department and contribute to the recommendations from health authorities. This pilot study is of particular relevance in the context of emerging epidemics of severe acute respiratory diseases.

Supplementary Information

The online version contains supplementary material available at 10.1186/s13613-021-00884-8.

Pediatric influenza and illness severity: what is known and what questions remain?

PURPOSE OF REVIEW

Influenza causes a range of illnesses in children, from uncomplicated self-limited illness to severe disease and death. This review provides an update on the severity and burden of influenza in US children over recent seasons.

RECENT FINDINGS

The 2017-2018 influenza season was widespread and severe across all ages, including children. Disease severity is influenced by influenza virologic characteristics and host factors, as well as public health interventions such as influenza vaccination and antiviral treatment. In recent influenza A (H3N2)-predominant seasons (2016-2017 and 2017-2018), influenza vaccination effectiveness was higher in younger children compared with older children and adolescents, although the reasons for this are unclear. Interestingly, even in seasons when influenza A (H3N2) viruses predominate, influenza A (H1N1)pdm09 and B viruses can play a large role in severe pediatric disease. Although children less than 5 years of age and those with underlying medical conditions are at increased risk for severe disease, influenza-associated hospitalizations and deaths occur every season in healthy children.

SUMMARY

Influenza causes a substantial burden of outpatient visits, hospitalizations, and deaths among children. Ongoing research is important to better characterize factors that contribute to influenza severity, and to identify strategies to improve the impact of influenza vaccination and treatment.