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Vaccine Development

Vaccination is the best way to protect yourself from the flu. Flu vaccines have a very good safety track record.

  • Getting the flu vaccine creates antibodies in your body that protect you from infection.
  • Developing effective vaccines for the flu is challenging because flu strains change constantly.

How are vaccines developed for new and seasonal flu viruses?

Several different strains of flu viruses circulate each year. To protect people from infection, the National Institute of Allergy and Infectious Diseases (NIAID) laboratories develop new vaccines for seasonal flu viruses and animal strains that could become pandemics.

Although researchers are working to develop new ways to make flu vaccines, current flu vaccines start with chicken eggs. New flu strains identified as possible pandemics are injected into an egg to grow before being harvested and made into vaccines.

As our existing flu vaccine production processes improve, our ability to quickly respond to outbreaks and potential pandemics with strain-specific vaccines improves as well.

Learn more about recent advances in flu vaccination.

Learn more about vaccine production.

How do flu vaccines work?

Vaccines help develop immunity by imitating an infection. This type of infection does not cause illness, however. Instead, it causes your immune system to produce antibodies. Sometimes, after getting a vaccine, the imitation infection causes minor symptoms, such as fever. Such minor symptoms are normal and should be expected as the body builds immunity.

Once the imitation infection goes away, the body is left with a supply of “memory” antibodies that remember how to fight that disease in the future. However, it usually takes a few weeks  for the body to produce antibodies after vaccination.  Therefore, it is possible to get the flu if you are exposed to the virus just before or just after you get the vaccine because your body has not had enough time to provide protection.

Are there challenges to developing flu vaccines?

Although vaccination is the best way to protect people from the flu, developing vaccines presents two challenges:

  • Flu viruses are constantly changing or mutating. Seasonal vaccines, the shots we get each winter, protect against three and sometimes even four different flu viruses. Those viruses change and a new vaccine must be developed each year.
  • Animals, especially birds, carry many flu viruses. Sometimes these animal viruses mutate and become capable of infecting humans. These new flu variants are of great concern because humans have no acquired immunity to them. They have the potential of causing a pandemic, and it is essential to develop a new vaccine as quickly as possible.

Related Links

Selecting the Viruses in the Seasonal Influenza (Flu) Vaccine

FDA Approves FluBlok: First Flu Vaccine Made Using Recombinant DNA Technology

FDA Approves First Seasonal Influenza Vaccine Manufactured Using Cell Culture Technology

FDA Approves First Quadrivalent Vaccine to Prevent Seasonal Influenza

Community Immunity (“Herd Immunity”)

Vaccine Safety