INFORMATION ON THE INFLUENZA VACCINE DURING PREGNANCY OR BREASTFEEDING

What is the influenza vaccine?

Influenza vaccine is a shot that is given to train the immune system to recognize and defend against influenza (“flu”) virus, of which there are two main groups, or serotypes, known as A and B. New vaccines are produced each year, because influenza viruses evolve rapidly such that they can be very different from season to season in terms of how they are seen by the human immune system, and also because the immunity from previous years' vaccination weakens over time. Over the past several years, both weakened live attenuated (living but weakened) flu vaccines and inactivated (not living) have been produced, but as of the writing of this report data show that the inactivated influenza vaccines work better. Thus, for the 2017- 2018 flu season, inactivated influenza vaccine (IIV) is what is being given to most people getting influenza vaccine in North America.  The most commonly given influenza vaccine is designed to protect against four strains of flu virus, three of these being A and B serotypes, and the other being another common flu virus.