Are vaccines 100% effective?

First, no vaccine is 100% effective. To make vaccines safer than the disease, the bacteria or virus is killed or weakened (attenuated). For reasons related to the individual, not all vaccinated persons develop immunity. Most routine childhood vaccines are effective for 85% to 95% of recipients. read more

It could be the vaccine, the environment, or the host, or a combination. read more

Seasonal flu vaccines are designed to protect against infection and illness caused by the three or four influenza viruses (depending on vaccine) that research indicates will be most common during the flu season. read more

Vaccines Work. Vaccines are very effective — and they’re the best protection against many serious diseases. Most people who get vaccinated will have immunity (protection) against the disease. read more