Vaccines prevent diseases that can cause serious illness and even death. They also stop them from spreading, reducing the burden on families and health systems. It takes many years for a vaccine to make it through all the tests and trials required before it can be approved. Some vaccines can completely prevent disease and others reduce the severity of the illness. Even if you or your child has been vaccinated, you can still get the disease if enough of the people around you are not vaccinated. This is because pathogens (like viruses and bacteria) can change over time, making them harder for your immune system to recognize and fight. Widespread vaccination prevents outbreaks of diseases and allows those who cannot get a vaccine to be protected by “herd immunity”.
Almost all vaccines contain a small amount of the bacteria, virus or toxin that causes the disease, which has been weakened in the lab. They may also contain excipients, like water or salt; adjuvants, which help the active ingredient work better; stabilizers, such as gelatin; and preservatives, such as thimerosal. The thimerosal is added to protect the vaccines from contamination during production and storage.
Some diseases, such as smallpox and polio, have been eradicated because of vaccination. Others, such as influenza and measles, remain endemic in parts of the world because not everyone is up to date on their vaccinations. Getting vaccinated keeps children healthy and ready to learn, adults working and caring for their loved ones, and makes our communities safer places for all.