We report a fatal case of febrile encephalopathy in an 84-year-old man following administration of the live-attenuated chikungunya vaccine IXCHIQ® (VLA1553, Valneva SE) during the 2025 outbreak in Réunion Island. The patient, previously autonomous with stable comorbidities, developed fever, asthenia, and polyarthralgia 3 days post-vaccination. His condition rapidly deteriorated, with confusion, acute kidney injury, and hemodynamic instability requiring intensive care. Chikungunya virus RNA was detected in both serum and cerebrospinal fluid, with sequencing confirming the presence of the vaccine strain in both compartments. Despite broad-spectrum antimicrobials, antiviral therapy targeting herpesviruses, and hemodialysis, his neurological status worsened and he died 14 days after symptom onset. This case is the first fatal adverse event officially recognized by French health authorities as plausibly related to VLA1553 vaccine. It raises concerns regarding potential neuroinvasive disease following vaccination in elderly individuals and highlights the importance of close clinical and virological evaluation in post-vaccination adverse events during outbreak settings.

Background: Health literacy involves individuals’ knowledge, personal skills, and confidence to take action to evaluate and appraise health-related information and improve their health or that of their community. Objective: This study aimed to analyze the association between health literacy and attitude toward vaccines, adjusted with other factors. Methods: We used the SLAVACO Wave 3, a survey conducted in December 2021 among a sample of 2022 individuals, representative of the French adult population. We investigated factors associated with the attitude toward vaccines using respondents’ different sociodemographic data, health literacy levels, and the health care system confidence levels using a multinomial logistic regression analysis. Results: Among the participants, 440.4 (21.8%) were classified as “distrustful of vaccines in general,” 729.2 (36.1%) were “selectively hesitant,” and 852.4 (42.2%) were “nonhesitant.” In our model, the level of health literacy was not statistically different between the “distrustful of vaccines in general” and the “selectively hesitant” (P=.48), but it was associated with being a “nonhesitant” (adjusted odds ratio [aOR] 1.86, 95% CI 1.25-2.76). The confidence in the health care system was a strong predictor for a “nonhesitant” attitude toward vaccines (aOR 12.4, 95% CI 7.97-19.2). We found a positive correlation of 0.34 (P<.001) between health literacy and confidence in the health care system, but the interaction term between health literacy and health care system confidence was not significant in our model. Conclusions: Health literacy was associated with a “nonhesitant” attitude toward vaccines. The findings demonstrated that health literacy and confidence in the health care system are modestly correlated. Therefore, to tackle the subject of vaccine hesitancy, the main focus should be on increasing the population’s confidence and on increasing their health literacy levels or providing vaccine information addressing the needs of less literate citizens.

Question addressed by the study: Do three coronavirus disease 2019 (COVID-19) vaccine doses induce a serological response in lung transplant recipients?Methods: We retrospectively included 1071 adults (551 (52%) males) at nine transplant centres in France. Each had received three COVID-19 vaccine doses in 2021, after lung transplantation. An anti-spike protein IgG response, defined as a titre >264 BAU·mL⁻¹after the third dose (median (interquartile range (IQR)) 3.0 (1.7–4.1) months), was the primary outcome and adverse events were the secondary outcomes. Median (IQR) age at the first vaccine dose was 54 (40–63) years and median (IQR) time from transplantation to the first dose was 64 (30–110) months.Results: Median (IQR) follow-up after the first dose was 8.3 (6.7–9.3) months. A vaccine response developed in 173 (16%) patients. Factors independently associated with a response were younger age at vaccination, longer time from transplantation to vaccination and absence of corticosteroid or mycophenolate therapy. After vaccination, 51 (5%) patients (47 non-responders (47/898 (5%)) and four (4/173 (2%)) responders) experienced COVID-19, at a median (IQR) of 6.6 (5.1–7.3) months after the third dose. No responders had severe COVID-19 compared with 15 non-responders, including six who died of the disease.Conclusions: Few lung transplant recipients achieved a serological response to three COVID-19 vaccine doses, indicating a need for other protective measures. Older age and use of mycophenolate or corticosteroids were associated with absence of a response. The low incidence of COVID-19 might reflect vaccine protectionviacellular immunity and/or good adherence to shielding measures.

The efficacy of vaccines against coronavirus disease 2019 (COVID-19) has now been well established in phase III clinical trials. However, clinical studies based on real-world data remain critical to assess vaccines effectiveness (VE), especially in specific populations and against variants of concern (VOC). This review presents the principles and methods of VE studies and the main available results on VE of COVID-19 vaccines at the time of Omicron circulation. References for this narrative review were identified through searches of PubMed database up to 13 September 2022. The results of phase III clinical trials have been globally confirmed by VE in real-life studies, including in the elderly. Emergence of VOC Omicron emphasized the importance of booster doses to maintain a high level of protection against severe forms. There are still numerous challenges regarding booster(s) and duration of immunity, particularly in specific subpopulations, and regarding the need for adapted vaccines.

Background: We aimed to compare the characteristics of human metapneumovirus (hMPV) infection with influenza A and B virus (FLUV) and respiratory syncytial virus (RSV) infections in adults hospitalized with influenza-like illness (ILI). Methods: We conducted a post hoc analysis of adult patients hospitalized with community-acquired ILI who were enrolled in the FLUVAC study at 5 French referral hospitals from 2012 to 2022. Results: At least 1 respiratory virus was detected in 3620 of 6618 patients (55%), including FLUV (1524/3620 [42%]), RSV (248/3620 [7%]), and hMPV (162/3620 [5%]). hMPV+ patients, when compared to FLUV+ patients were more likely to develop at least 1 complication (60% [86/143] vs 50% [716/1435]; P = .02), especially acute heart failure, which occurred twice as often in hMPV+ during the hospital stay (22% [32/143] vs 11% [160/1434]; P < .001). The rates of respiratory (30% [43/143] vs 32% [70/216]; P = .73) or cardiac (22% [32/143] vs 15% [33/216]; P = .09) complications did not differ between hMPV+ and RSV+ patients. The in-hospital all-cause death rate was similar among all 3 populations (4% hMPV+, 4% FLUV+, and 5% RSV+). Conclusions: Hospitalized hMPV infections affect older patients with multiple chronic conditions who face frequent cardiac and pulmonary complications during hospitalization more frequently than with influenza and similar to RSV.