Nasovac-S Vaccine helps protect you from influenza (flu). It works by exposing you to a small dose of the flu virus which helps your body to develop immunity against the disease. It will not treat an existing flu virus infection. Nasovac-S Vaccine should be used as you have been advised by your doctor. It is usually given just before the cold season when the flu virus begins to increase. Normally you should blow your nose gently before using it, keep one nostril closed while applying the medicine into the other, and then sniff hard to make sure it reaches deep into the nose. Then repeat for the other nostril. The most common side effects of this medicine are nasal discomfort, sneezing, runny nose, chills, and facial swelling. It may also cause fever, headache, fatigue, sore throat, cough, wheezing, and nausea. These are usually mild but if they bother you or do not go away, let your doctor know. Your doctor may be able to suggest ways of preventing or reducing them. Before using this medicine, you should tell your doctor if you have any preexisting medical conditions or if you have ever had an allergic reaction to a vaccine. Some other medicines may react with the flu vaccine so talk to your doctor about other medications you are taking as well. As with any vaccine, this treatment may not fully protect everybody, although it will reduce the symptoms of the flu if you get it. This vaccine is safe for use in adults and children over 2 years old. Ask your doctor for advice before using this medicine if you are pregnant or breastfeeding.