Influenza Vaccination

The goal of this clinical trial is to learn if a family-physician nudge intervention works to improve influenza vaccination among adults aged 55 years and older in China. Three independent, parallel cluster randomized controlled trials will be conducted under three distinct vaccine payment policies, i.e. free vaccination for those older than 65 years and self-paid vaccination for those \<65 years in rural areas, and partially insurance-covered vaccination in urban areas. The main questions it aims to answer are: 1. Does the family-physician nudge intervention increase influenza vaccination uptake among older adults? How does the effectiveness of the nudge intervention vary under different payment policies？ 2. Is the family-physician nudge intervention cost-effective, acceptable, feasible, and potentially sustainable in primary care settings? Researchers will compare an intervention group receiving a family-physician nudge with a control group receiving routine care to see if the nudge is effective at increasing influenza vaccination among older adults. Participants will: 1. Be recruited at community health service centers and cluster-randomized by their family physicians into one of two groups. 2. Receive either a physician nudge (provider recommendation by an endowment-framing educational pamphlet + default appointment + a follow-up reminder) or routine health education. 3. Have their influenza vaccination status verified through the immunization information system at the end of the trial.

The goal of this clinical trial is to compare immune responses to different influenza vaccine formulations in older adults and to understand how immune aging and repeated annual influenza vaccination affect these responses. The main questions it aims to answer are: * Do standard dose, MF59 adjuvanted, and high dose influenza vaccines produce different immune responses in adults aged 65 years or older? * How does immune aging affect responses to different influenza vaccine formulations? * How do immune responses change with repeated annual influenza vaccination, and do these changes differ among vaccine formulations? Researchers will compare older adults who receive a standard dose, MF59 adjuvanted, or high dose influenza vaccine. Younger adults aged 19-49 years who receive a standard dose influenza vaccine will also be included as a reference group to help evaluate age related differences in immune responses. Participants will: * Receive an influenza vaccine. * Provide blood samples before and after vaccination to measure antibody and other immune responses. * Some participants will provide additional blood or nasal samples for more detailed evaluation of immune responses.

Some authors have proposed the use of the flu vaccine to reduce the severity of COVID-19 cases, while some have proposed the use of ACE Inhibitors (ACEI) or Angiotensin Receptor blockers (ARB), since this virus shares hemagglutinin as a transmission mechanism and acts on the ACE2 enzyme during infection. Other authors described how none of the elderly patients receiving antihistamines and azythromycin in two nursing homes in Toledo -Spain- during the first wave died or needed hospital admission, even considering that 100% of residents had a positive serological test after that wave. Other authors have described a positive evolution in patients receiving amantadine for their Parkinson's disease. The aim is to evaluate whether the admitted patients who are previously vaccinated or those who were already receiving these treatments showed a better evolution.

The goal of this intervention study is to learn if giving children influenza vaccinations in early childhood education facilities (i.e., daycare) will increase vaccination coverage compared to giving vaccinations only at healthcare. The main question it aims to answer is: • Does offering children nasal influenza vaccine in daycare result in higher proportion of children getting influenza vaccine. Researchers will compare daycare setting and healthcare setting as the location of giving influenza vaccines to children to see if more children will get vaccinated if they have an opportunity to receive nasal influenza vaccine at daycare. Participants in the intervention group will: • Have the opportunity to receive influenza vaccine in the daycare or in the healthcare Participants in the comparison group will: • Have the opportunity to receive influenza vaccine in the healthcare only