Quadrivalent Influenza Vaccine is a type of flu shot designed to protect against four different strains of the influenza virus. In this clinical trial, the vaccine is being tested in two different strengths to see which one is more effective in preventing serious illnesses like the flu and pneumonia in older adults. The goal is to find out if a higher dose of the vaccine offers better protection compared to the standard dose. This vaccine works by helping your body build up its defense system against the flu, reducing the chances of getting sick or needing to go to the hospital.

Influenza – Influenza, commonly known as the flu, is a contagious respiratory illness caused by influenza viruses. It primarily affects the nose, throat, and sometimes the lungs. The disease typically begins suddenly and can cause symptoms such as fever, cough, sore throat, runny or stuffy nose, muscle or body aches, headaches, and fatigue. In some cases, it can lead to more severe complications, especially in older adults and those with weakened immune systems. The virus spreads through droplets when an infected person coughs, sneezes, or talks. It can also spread by touching surfaces contaminated with the virus and then touching the face.

Pneumonia – Pneumonia is an infection that inflames the air sacs in one or both lungs, which may fill with fluid or pus. It can be caused by a variety of organisms, including bacteria, viruses, and fungi. Symptoms of pneumonia can include cough with phlegm or pus, fever, chills, and difficulty breathing. The disease can range from mild to severe, with severity often depending on the type of germ causing the infection, as well as the age and overall health of the individual. Pneumonia can be spread through airborne droplets from a cough or sneeze, or by touching contaminated surfaces. It is more common in older adults, infants, and those with weakened immune systems.