http://www.ajpmonline.org/article/S0749379722001313/pdf

The Association Between Previous Influenza Vaccination and COVID-19 Infection Risk and Severity: A Systematic Review and Meta-analysis

https://doi.org/10.1016/j.mad.2022.111672

Immunosenescence and COVID-19

SARS-CoV-2 and influenza are the main respiratory viruses for which effective vaccines are currently available. Strategies in which COVID-19 and influenza vaccines are administered simultaneously or combined into a single preparation are advantageous and may increase vaccination uptake. Here, we comprehensively review the available evidence on COVID-19/influenza vaccine co-administration and combination vaccine candidates from the standpoints of safety, immunogenicity, efficacy, policy and public acceptance. While several observational studies have shown that the trained immunity induced by influenza vaccines can protect against some COVID-19-related endpoints, it is not yet understood whether co-administration or combination vaccines can exert additive effects on relevant outcomes. In randomized controlled trials, co-administration has proved safe, with a reactogenicity profile similar to that of either vaccine administered alone. From the immunogenicity standpoint, the immune response towards four influenza strains and the SARS-CoV-2 spike protein in co-administration groups is generally non-inferior to that seen in groups receiving either vaccine alone. Several public health authorities have advocated co-administration. Different combination vaccine candidates are in (pre)-clinical development. The hesitancy towards vaccine co-administration or combination vaccines is a multifaceted phenomenon and may be higher than the acceptance of either vaccine administered separately. Public health implications are discussed.

/pdf/covid-19-and-seasonal-influenza-vaccination-cross-protection-8qc0deqd.pdf

COVID-19 and Seasonal Influenza Vaccination: Cross-Protection, Co-Administration, Combination Vaccines, and Hesitancy

Background: Prior studies have found a reduced risk of dementia of any etiology following influenza vaccination in selected populations, including veterans and patients with serious chronic health conditions. However, the effect of influenza vaccination on Alzheimer’s disease (AD) risk in a general cohort of older US adults has not been characterized. Objective: To compare the risk of incident AD between patients with and without prior influenza vaccination in a large US claims database. Methods: Deidentified claims data spanning September 1, 2009 through August 31, 2019 were used. Eligible patients were free of dementia during the 6-year look-back period and≥65 years old by the start of follow-up. Propensity-score matching (PSM) was used to create flu-vaccinated and flu-unvaccinated cohorts with similar baseline demographics, medication usage, and comorbidities. Relative risk (RR) and absolute risk reduction (ARR) were estimated to assess the effect of influenza vaccination on AD risk during the 4-year follow-up. Results: From the unmatched sample of eligible patients (n = 2,356,479), PSM produced a sample of 935,887 flu–vaccinated-unvaccinated matched pairs. The matched sample was 73.7 (SD, 8.7) years of age and 56.9% female, with median follow-up of 46 (IQR, 29–48) months; 5.1% (n = 47,889) of the flu-vaccinated patients and 8.5% (n = 79,630) of the flu-unvaccinated patients developed AD during follow-up. The RR was 0.60 (95% CI, 0.59–0.61) and ARR was 0.034 (95% CI, 0.033–0.035), corresponding to a number needed to treat of 29.4. Conclusion: This study demonstrates that influenza vaccination is associated with reduced AD risk in a nationwide sample of US adults aged 65 and older. 

/pdf/risk-of-alzheimers-disease-following-influenza-vaccination-a-1lyhd04q.pdf

Risk of Alzheimer’s Disease Following Influenza Vaccination: A Claims-Based Cohort Study Using Propensity Score Matching

Trained immunity-related vaccines: innate immune memory and heterologous protection against infections.

Non-specific protective effects of certain vaccines have been reported, and long-term boosting of innate immunity, termed trained immunity, has been proposed as one of the mechanisms mediating these effects. Several epidemiological studies suggested cross-protection between influenza vaccination and COVID-19. In a large academic Dutch hospital, we found that SARS-CoV-2 infection was less common among employees who had received a previous influenza vaccination: relative risk reductions of 37% and 49% were observed following influenza vaccination during the first and second COVID-19 waves, respectively. The quadrivalent inactivated influenza vaccine induced a trained immunity program that boosted innate immune responses against various viral stimuli and fine-tuned the anti-SARS-CoV-2 response, which may result in better protection against COVID-19. Influenza vaccination led to transcriptional reprogramming of monocytes and reduced systemic inflammation. These epidemiological and immunological data argue for potential benefits of influenza vaccination against COVID-19, and future randomized trials are warranted to test this possibility.

/pdf/induction-of-trained-immunity-by-influenza-vaccination-3wear5noq2.pdf

Induction of trained immunity by influenza vaccination - impact on COVID-19.

For almost 30 years, the term "holobiont" has referred to an ecological unit where a host (e.g., human) and all species living in or around it are considered together. The concept highlights the complex interactions between the host and the other species, which, if disturbed may lead to disease and premature aging. Specifically, the impact of microbiome alterations on the etiology of acute lymphoblastic leukemia (ALL) in children is not fully understood, but has been the focus of much research in recent years. In ALL patients, significant reductions in microbiome diversity are already observable at disease onset. It remains unclear whether such alterations at diagnosis are etiologically linked with leukemogenesis or simply due to immunological alteration preceding ALL onset. Regardless, all chemotherapeutic treatment regimens severely affect the microbiome, accompanied by severe side effects, including mucositis, systemic inflammation, and infection. In particular, dominance of Enterococcaceae is predictive of infections during chemotherapy. Long-term dysbiosis, like depletion of Faecalibacterium, has been observed in ALL survivors. Modulation of the microbiome (e.g., by fecal microbiota transplant, probiotics, or prebiotics) is currently being researched for potential protective effects. Herein, we review the latest microbiome studies in pediatric ALL patients.

The Microbiome in Childhood Acute Lymphoblastic Leukemia.

/pdf/induction-of-trained-immunity-by-influenza-vaccination-34a7ii7ptf.pdf

Nadine Rüchel

Papers

Induction of trained immunity by influenza vaccination - impact on COVID-19.

The Microbiome in Childhood Acute Lymphoblastic Leukemia.

Induction of trained immunity by influenza vaccination - impact on COVID-19